Electrolyte correction and fluid support

ElectrolyteRx

Move quickly between correction formulas, diagnostic workups, replacement guidance, emergency hyperkalemia sequencing, and rate-limited sodium correction without losing clinical context.

11 clinical modulesDiagnosis and dosing supportCorrection-rate safeguards

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Corrected Calcium for Albumin

Payne formula (1973). Estimates total calcium as it would appear if albumin were normal — does not measure ionized calcium.

Measured Total Calcium (mg/dL)

Serum Albumin (g/dL)

Enter values and click Calculate.

Free Water Deficit

Estimates the water deficit driving hypernatremia, based on total body water. Does not itself set a safe correction rate — see the Hypernatremia Rate Limit tab to translate this into a rate.

Age (years)

Sex

Actual Body Weight (kg)

Current Serum Na (mEq/L)

Target Serum Na (mEq/L)

Enter values and click Calculate.

Maintenance IV Fluid Rate — Holliday-Segar

Weight-based maintenance fluid rate (the "4-2-1 rule"), derived from Holliday & Segar, Pediatrics 1957. Originally a pediatric formula; commonly extrapolated to adults but many adult protocols instead use a flat 25–30 mL/kg/day — see the note below before applying in adults.

Actual Body Weight (kg)

Enter weight and click Calculate.

Potassium / Magnesium / Phosphate / Calcium Replacement Reference

Adults onlyThe doses and bands on this tab are adult values. Children and neonates need weight-based doses (for example, the calcium gluconate label gives separate neonatal and pediatric mg/kg doses) — use a pediatric reference.

Common representative dosing bands, not a single universal standard — unlike the Payne, Holliday-Segar, or Katz/Hillier formulas above, exact replacement doses and infusion rates vary meaningfully by institution. Confirm against your institutional protocol, particularly infusion-rate limits and cardiac-monitoring requirements for IV replacement.

Potassium

Serum K⁺	Typical Replacement
3.0–3.4 mEq/L	40–60 mEq PO (divided doses; GI upset common with single large doses)
2.5–2.9 mEq/L	60–80 mEq, PO and/or IV combined
<2.5 mEq/L or symptomatic (arrhythmia, significant weakness)	IV KCl, typically 10 mEq/hr peripheral line (up to ~20 mEq/hr via central line with continuous cardiac monitoring) — institutional max infusion rates vary; recheck level after each 20–40 mEq infused

Concentration/rate limits — label vs. common institutional practiceThe FDA label for KCl injection concentrate says: if serum potassium is greater than 2.5 mEq/L, give at no more than 10 mEq/hour and at a concentration of up to 40 mEq/L, with a 24-hour total not exceeding 200 mEq; if urgent treatment is indicated (potassium less than 2 mEq/L with ECG changes and/or muscle paralysis) it may be infused very cautiously at up to 40 mEq/hour with continuous cardiac monitoring, and as much as 400 mEq may be given in 24 hours. The label for premixed KCl bags states that the highest concentrations (300 and 400 mEq/L) must be given exclusively by the central route. The commonly used institutional peripheral limit (≤10 mEq/100 mL, i.e. 100 mEq/L, and ≤10 mEq/hr) and central limit (up to ~20 mEq/100 mL, 20–40 mEq/hr with monitoring) are NOT in the concentrate label: its 40 mEq/L concentration limit applies at potassium above 2.5 mEq/L, so a 100 mEq/L peripheral bag is a higher concentration than that label figure rather than a more conservative one. The tool cannot reconcile the label and common practice for you — follow your institutional policy, and note KCl is an ISMP-designated high-alert medication regardless of route.

Magnesium

Serum Mg²⁺	Typical Replacement
1.0–1.5 mg/dL, asymptomatic	1–2 g MgSO₄ IV over 1–2 hr
<1.0 mg/dL or symptomatic (seizure, torsades de pointes)	1–2 g MgSO₄, diluted to ≤20%, IV at no more than 150 mg/min per the label (1 g takes at least ~7 min, 2 g at least ~14 min) for torsades; faster administration in unstable torsades is an emergency-practice decision outside the label. Otherwise 2 g IV over 1 hr, then reassess — consider a slower maintenance infusion for ongoing severe deficit

Renal impairmentReduce magnesium repletion dose and infusion rate in significant renal impairment — magnesium is renally cleared and accumulates; monitor levels more frequently.

Concentration/rate limits (FDA label)The 50% MgSO₄ stock solution must NEVER be injected IV undiluted — it is only given undiluted by the IM route. For IV use (push or infusion), it must first be diluted to a concentration of ≤20%; verify the pharmacy-prepared bag/syringe concentration is ≤20% before infusing peripherally or centrally. Maximum IV push rate is ≤150 mg/min (relevant to the torsades/seizure bolus above); for continuous infusion the label states no separate ceiling for hypomagnesemia (its 1–2 g/hour statement is in the eclampsia/pre-eclampsia dosing section, not hypomagnesemia).

Phosphate

Serum Phosphate	Typical Replacement
1.8 to <2.5 mg/dL, asymptomatic, able to take oral	Oral phosphate (e.g., potassium or sodium phosphate) — divided doses, GI tolerance limits total
1.8 to <2.5 mg/dL, when oral replacement is not possible	IV phosphorus 0.16–0.31 mmol/kg (potassium phosphates label, Table 2; actual body weight — consider adjusted body weight when well above ideal), maximum 45 mmol phosphorus per single dose
1.0 to <1.8 mg/dL	IV phosphorus 0.32–0.43 mmol/kg (same label table and limits), infused no faster than the label's 6.8 mmol/hr peripheral maximum (higher rates only via a central line per the label)
<1.0 mg/dL or symptomatic	IV phosphorus 0.44–0.64 mmol/kg (same label table, 45 mmol single-dose maximum), infused within the label's rate limits — monitor calcium (risk of hypocalcemia/precipitation with concurrent calcium-containing fluids) and recheck the level after infusion

Potassium phosphates: label contraindicationsThe potassium phosphates injection label contraindicates use in hyperkalemia, in severe renal impairment (eGFR below 30 mL/min/1.73 m²) or end-stage renal disease, in hyperphosphatemia, and in hypercalcemia or significant hypocalcemia. A normal potassium does not clear a patient with eGFR below 30 or on dialysis. Use sodium phosphates only after reviewing that product's own label and the patient's sodium load, and with nephrology or pharmacy input.

Salt selectionChoose potassium vs. sodium phosphate based on the patient's potassium status — do not add a potassium-containing phosphate salt to a hyperkalemic patient. In renal impairment a normal serum potassium does not make potassium phosphates safe (see the label contraindication above); prefer sodium phosphate unless the prescriber has a reason.

Peripheral infusion rate (FDA label)Current potassium phosphate injection labeling specifies a peripheral infusion rate of approximately 6.8 mmol phosphorus/hr (≈10 mEq potassium/hr), with ECG monitoring recommended above that rate, and a maximum single/initial dose of 45 mmol phosphorus. A current FDA label specifically for sodium phosphate injection with its own distinct rate limit was not located — use the potassium phosphate rate as the more conservative reference if using the sodium salt, and confirm against your institutional protocol.

Calcium

Corrected Serum Calcium

Typical Replacement

7.5 to <8.5 mg/dL, asymptomatic

Oral calcium carbonate or citrate ± vitamin D — address the underlying cause (vitamin D deficiency, hypomagnesemia, hypoparathyroidism)

<7.5 mg/dL or symptomatic (tetany, seizures, QTc prolongation)

Calcium gluconate 1-2 g (10-20 mL of 10%) diluted to 10–50 mg/mL (e.g. 1 g in at least 20 mL) per the label, IV over 10-20 minutes (never faster than 200 mg/min in adults), followed by a continuous infusion if ongoing repletion is needed (e.g., post-thyroidectomy hypoparathyroidism) — check ionized calcium and magnesium (correct hypomagnesemia first if present, as it blunts PTH response and repletion will not hold otherwise)

This is NOT the same indication or rate as the Hyperkalemia tab's calcium doseThe Hyperkalemia Management tab's calcium gluconate 1000 mg IV over at least 5 minutes (per the FDA label's 200 mg/min adult bolus rate cap) is for EMERGENT cardiac membrane stabilization in hyperkalemia — a different, faster protocol than routine symptomatic hypocalcemia repletion above. Do not confuse the two indications.

Concentration/rate limits (FDA label, calcium gluconate)Bolus dilution 10-50 mg/mL; continuous-infusion dilution 5.8-10 mg/mL. Maximum infusion rate 200 mg/min in adults, 100 mg/min in pediatric/neonatal patients. The label does not state a separate peripheral-specific concentration cap distinct from these dilution ranges, but does warn of extravasation/tissue necrosis — secure IV access is required regardless of route. (Calcium chloride, in contrast, requires central/deep-vein administration only per its own current label — see the Hyperkalemia tab for that distinction.)

⚠ Hyperkalemia Emergency Management

Stratifies urgency and sequences treatment. Per current nephrology consensus (Palmer & Clegg, Nephrol Dial Transplant 2024), the ECG is not reliable — it can remain normal despite severe hyperkalemia, so a normal ECG must never be used to defer treatment at K⁺ >6.0 mEq/L. Conversely, ANY ECG change (even at a lower K⁺, especially if the level rose rapidly) mandates emergent treatment regardless of the lab value.

Adults (18 years and older) onlyThe doses and thresholds on this tab are adult values. Children and neonates need weight-based dosing and different potassium thresholds — use a pediatric protocol and poison control or pediatric nephrology/critical care input; do not apply this sequence to a child.

Serum Potassium (mEq/L)

ECG changes present?

Concurrent significant metabolic acidosis?

Making urine / residual renal function?

Digoxin?

Ongoing potassium load or rapid rise expected? (rhabdomyolysis/crush, tumor lysis, hemolysis, GI bleeding, burns, reperfusion, recent succinylcholine after burns/trauma/denervation)

Kidney failure? (AKI, advanced CKD or dialysis-dependent)

Baseline glucose (mg/dL) — optional

Enter serum potassium and click Assess.

Step 1 — Confirm Hypotonic Hyponatremia

Before using volume status or urine studies to find the CAUSE, confirm this is actually hypotonic (true, water-excess) hyponatremia. Hyperglycemia (translocational) and pseudohyponatremia (severe hyperlipidemia/hyperproteinemia, with an older ion-selective-electrode assay) can produce a low measured sodium that is NOT hypotonic — routing these into the volume-status/SIADH tree below would misclassify them.

Measured serum osmolality (mOsm/kg) — preferred

Serum glucose (mg/dL) — if osmolality not available

Severe hyperlipidemia or hyperproteinemia (e.g. myeloma) present?

Enter serum osmolality (preferred) or glucose, then click Check Tonicity, before proceeding to Step 2.

Step 2 — Assess Volume Status

Once hypotonicity is confirmed in Step 1, the volume-status exam is the next branch point for diagnosing the CAUSE of hyponatremia — this is separate from the correction-RATE safety check in the Hyponatremia Rate Limit tab. Assess before checking urine studies below.

Category	Exam findings
Hypovolemic	Orthostatic hypotension/tachycardia, dry mucous membranes, decreased skin turgor, flat neck veins, low-normal or low blood pressure
Euvolemic	No edema, no ascites, normal JVP, no signs of volume depletion — most common overall category
Hypervolemic	Peripheral edema, ascites, elevated JVP, pulmonary crackles/effusion, jaundice/stigmata of liver disease

Step 3 — Interpret Urine Studies

Urine sodium and osmolality narrow the differential once volume status is assessed. Urine Na <30 mEq/L generally identifies both hypovolemic AND hypervolemic hyponatremia (kidneys appropriately retaining sodium); Urine Na >30 mEq/L in a clinically euvolemic patient, with urine osmolality >100 mOsm/kg, supports SIADH.

Volume status

Urine Sodium (mEq/L)

Urine Osmolality (mOsm/kg) — optional

Currently on diuretics?

Select volume status and enter urine studies, then click Interpret.

Etiology & Treatment by Category

Hypovolemic

Renal losses (urine Na typically >30 mEq/L): diuretics — especially thiazides; mineralocorticoid deficiency/primary adrenal insufficiency; salt-wasting nephropathy; cerebral salt wasting (neurocritical care context, distinguished from SIADH mainly by volume status). Extrarenal losses (urine Na typically <30 mEq/L): GI losses (vomiting, diarrhea), burns, third-spacing (pancreatitis, ileus). Treatment: isotonic (0.9%) saline.

Euvolemic

SIADH is the most common cause of hyponatremia overall. Diagnostic criteria: hypotonic hyponatremia, clinical euvolemia, urine osmolality >100 mOsm/kg, urine sodium usually >30 mEq/L (cited as >30-40 mEq/L across sources — not a single precise cutoff), normal thyroid and adrenal function, and no diuretic use. Causes: malignancy (small-cell lung cancer is the classic association), CNS disorders (stroke, hemorrhage, infection, trauma), pulmonary disease (pneumonia, TB, positive-pressure ventilation), and drugs (SSRIs, carbamazepine/oxcarbazepine, cyclophosphamide, vincristine/vinblastine, antipsychotics, MDMA, NSAIDs, opioids). Treatment: fluid restriction <1 L/day is first-line, tightened to <500 mL/day if the urine-to-serum electrolyte ratio (urine [Na+K]/serum Na) is >1 — a ratio this high predicts fluid restriction alone is likely to fail at looser targets. Salt tablets and/or a loop diuretic (to blunt urine-concentrating ability) are used adjunctively. 3% saline is used for severe/symptomatic hyponatremia regardless of cause (see the 3% Saline tab). Tolvaptan (vasopressin receptor antagonist): FDA boxed warning — initiate and re-initiate only in a hospital with close serum sodium monitoring (too-rapid correction risks osmotic demyelination). Other label cautions: do not use for more than 30 days (liver injury risk); avoid in patients with underlying liver disease, including cirrhosis; avoid use with hypertonic saline; avoid fluid restriction during the first 24 hours of therapy.

Primary polydipsia — urine osmolality <100 mOsm/kg is the key differentiator from SIADH; treatment is water restriction and addressing the underlying psychiatric/compulsive drinking behavior, not the SIADH pharmacologic approach.

Low dietary solute intake ("tea and toast," beer potomania) — limited dietary osmoles restrict the kidney's free-water excretion capacity; urine osmolality and sodium are often (but not reliably) low. High risk of overly rapid auto-correction once normal eating/refeeding resumes — recheck sodium frequently.

Hypothyroidism — typically only severe/myxedema causes clinically significant hyponatremia; treat with thyroid hormone replacement.

Secondary adrenal insufficiency — cortisol deficiency removes a tonic inhibitor of ADH release, producing an SIADH-like picture that resolves with glucocorticoid replacement, not fluid restriction — check morning cortisol/ACTH stimulation if suspected, especially with a history of chronic steroid use or pituitary disease.

Hypervolemic

Heart failure, cirrhosis, nephrotic syndrome, advanced CKD — mechanism is effective arterial blood volume depletion (reduced cardiac output, splanchnic vasodilation in cirrhosis, reduced GFR) triggering non-osmotic ADH release despite total-body volume/sodium excess. Urine Na is usually <30 mEq/L except in advanced CKD. Treatment: sodium AND fluid restriction, loop diuretics, and treatment of the underlying disease — NOT isotonic saline, which would worsen volume overload. Tolvaptan is FDA-labeled for hypervolemic hyponatremia including heart failure, but current labeling advises avoiding it in patients with underlying liver disease, including cirrhosis specifically.

⚠ Severe Symptomatic Hyponatremia — 3% NaCl Bolus Protocol

For severe symptoms (seizures, obtundation, delirium, coma) with confirmed hypotonic hyponatremia — bolus 3% NaCl, repeated as needed, is favored over a calculated continuous infusion as the first-line approach for hyponatremic encephalopathy. Two distinct protocols are in use — this is NOT one blended regimen, select which one your institution follows: the US expert panel approach (Verbalis et al., Am J Med 2013, as summarized by Sterns, CJASN 2018) uses 100 mL over 10 minutes, repeated up to three times as needed (the Baek 2021 SALSA trial — a Korean randomized trial — supports bolus therapy and used weight-based dosing, not this volume); the European Hyponatraemia Guideline (Spasovski et al., 2014, on behalf of the Hyponatraemia Guideline Development Group — paywalled, not read directly in this build; figure corroborated by multiple secondary clinical references) recommends 150 mL over 20 minutes, up to 3 doses. A 2025 systematic review/meta-analysis (3 studies, 290 patients) found bolus and continuous infusion equally safe and effective, with no significant difference in overcorrection, but did not itself resolve which bolus volume/duration is preferred.

Severe symptoms confirmed? (seizure, obtundation, delirium, coma)

Confirmed hypotonic hyponatremia?

Protocol

Age (years)

Sex

Actual Body Weight (kg)

Current Serum Na (mEq/L)

Sodium at start of THIS 24h window (mEq/L)

High risk for ODS present?

Enter values and click Calculate.

⚠ Mild-to-Moderate Symptoms / Ongoing Correction — Continuous 3% NaCl Infusion (Adrogué-Madias Formula)

For mild-to-moderate symptoms (fatigue, nausea, confusion without severe encephalopathy) or for planning ongoing correction after the initial bolus-phase target has been reached, a slow continuous infusion using the sodium deficit/Adrogué-Madias formula is used instead of repeated boluses. This is a starting-point calculation, not a prediction you can trust unmonitored — the formula assumes no ongoing sodium or water loss, which is frequently wrong in practice (see the worked example below). This tab now enforces the applicable 24h correction ceiling directly — it will not calculate an infusion for a rise beyond what remains allowable.

Indication

Confirmed hypotonic hyponatremia? (Step 1 of the Diagnostic Workup tab, or otherwise excludes hyperglycemia/pseudohyponatremia)

Age (years)

Sex

Actual Body Weight (kg)

Current Serum Na (mEq/L)

Desired Rise in Serum Na (mEq/L)

Over How Many Hours?

Which 24h correction window is this?

Sodium at start of THIS 24h window (mEq/L)

High risk for ODS present?

Enter values and click Calculate.

⚠ Hyponatremia Correction Rate Limit

Overly rapid correction of chronic/subacute hyponatremia risks osmotic demyelination syndrome (ODS). This module tracks the rise against the applicable ceiling and flags overcorrection. The ceiling differs between the first 24 hours of treatment and every 24-hour period after that — select which window this reading falls in.

Which 24-hour window is this reading in?

Sodium at Start of This 24h Window (mEq/L)

Current / Most Recent Sodium (mEq/L)

High risk for ODS present (chronic alcohol use, malnutrition/cirrhosis, hypokalemia, hypoxia, Na ≤105 mEq/L, or already-chronic hyponatremia)

Enter values and click Calculate.

Step 1 — Interpret Urine Osmolality

Urine osmolality is the key first branch point for diagnosing the CAUSE of hypernatremia — separate from the Free Water Deficit and Hypernatremia Rate Limit tabs, which handle treatment math once the cause is known. This interpretation only applies to confirmed hypotonic polyuria with paired plasma data — enter both below before interpreting.

Confirmed polyuria? (urine output >~3 L/24h, or >40-50 mL/kg/24h)

Measured plasma/serum osmolality (mOsm/kg) — preferred

Serum sodium (mEq/L) — use if osmolality unavailable

Urine Osmolality (mOsm/kg)

Confirm polyuria, enter paired plasma and urine osmolality, then click Interpret.

Step 2 — Desmopressin (DDAVP) Challenge Test

If Step 1 suggests diabetes insipidus (inappropriately dilute urine), this test distinguishes central from nephrogenic DI. This must be performed under direct medical supervision in a monitored inpatient or closely observed setting — oral/intranasal desmopressin absorption is too unpredictable, and hyponatremic complications are possible, for this to be run as an unsupervised outpatient test. Where available, prefer referral to endocrinology and a copeptin-based assay over the classic water-deprivation/desmopressin test (see the evolving-reference-standard note below). Protocol if performed (UK EMC desmopressin nasal spray SPC): after water deprivation, restrict fluids from 1 hour before to 8 hours after the dose; empty the bladder at dosing; discard the first hour of urine; measure urine osmolality before dosing and again at 2 and 4 hours post-dose.

Urine Osmolality Before DDAVP (mOsm/kg)

Urine Osmolality After DDAVP (mOsm/kg)

Enter both values and click Calculate.

Cutoff varies across sources — and the reference standard is evolving>50% rise for central DI and <15% for complete nephrogenic DI are the most commonly cited cutoffs, but a 2024 retrospective proposed a refined ≥54% threshold (small nephrogenic-DI cohort, limited generalizability), and partial responses in the 15-50% range are genuinely ambiguous (partial central DI and partial nephrogenic DI overlap here). Contemporary literature (copeptin-based testing, e.g., Fenske et al. NEJM 2018; Winzeler et al. Lancet 2019) argues copeptin assays are more accurate and are displacing the classic water-deprivation/desmopressin test as the reference standard where available.

Etiology Reference

Central Diabetes Insipidus

Causes: idiopathic, head trauma, pituitary/hypothalamic surgery, cranial neoplasm (craniopharyngioma, germinoma, metastases), infiltrative disease (sarcoidosis, histiocytosis), ischemic/hypoxic encephalopathy. Triphasic response after pituitary surgery: transient DI from axonal shock (first ~5-7 days) → SIADH-like antidiuresis around day 4-5 from uncontrolled release of stored ADH by degenerating axons → permanent DI if >80-90% of ADH-secreting neurons are destroyed. Treatment: desmopressin, FDA-labeled at 10-40 mcg/day intranasal, single or divided 2-3 times daily, individualized to urine output/nocturia.

Nephrogenic Diabetes Insipidus

Lithium is the leading acquired cause (reduced AQP2 channel expression in collecting-duct principal cells with chronic use). Other causes: hypercalcemia, hypokalemia, congenital AVPR2/AQP2 mutations, post-obstructive uropathy, and drugs including foscarnet and demeclocycline. Treatment: thiazide diuretic + low-sodium/low-protein diet, sometimes with amiloride (particularly useful in lithium-induced NDI — blocks ENaC, the channel lithium uses to enter principal cells) or an NSAID as adjunct. The thiazide "paradox": mild volume contraction increases proximal sodium/water reabsorption, delivering less water to the (defective) collecting duct — reducing urine output independent of the underlying concentrating defect.

Hypotonic Fluid Loss (non-DI)

Extrarenal: osmotic diarrhea, vomiting/NG drainage, burns, sweating. Renal: osmotic diuresis (hyperglycemia/glucosuria, mannitol, urea-driven diuresis from high-protein tube feeds/azotemia), post-obstructive diuresis. Insensible: fever, mechanical ventilation without adequate humidification.

Sodium Gain

Iatrogenic (hypertonic saline or sodium bicarbonate administration — common in cardiac arrest/severe acidosis management), primary hyperaldosteronism, rare accidental/intentional salt poisoning (including improperly mixed infant formula — a real, documented pediatric entity).

Once the cause is identifiedFor non-DI causes and as a general framework, use the Free Water Deficit tab to estimate the water deficit, and the Hypernatremia Rate Limit tab to keep correction within a safe rate — this workup tab does not duplicate that math.

⚠ Hypernatremia Correction Rate Limit

Overly rapid correction of hypernatremia risks cerebral edema. This module checks a planned correction against the commonly-used ceiling.

Earlier Sodium (mEq/L)

Current / Most Recent Sodium (mEq/L)

Hours Between These Two Values (required for a rate-based ceiling check — without it, the tool can only report the raw fall, not whether the pace is safe)

Enter values and click Calculate.

References

Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4(5893):643-646. (Corrected calcium formula: Corrected Ca (mg/dL) = Measured Ca + 0.8 × [4.0 − Albumin g/dL])
Das M, Baruah A. Total Versus Ionized Calcium: Valid Index of Calcium Status in Critically Ill Patients. Arch Pathol Lab Med. 2026 (online ahead of print). (Albumin-corrected calcium correlates poorly with measured ionized calcium in ICU patients — the correction is an estimate, not a substitute for ionized calcium when precision matters)
Katz MA. Hyperglycemia-induced hyponatremia — calculation of expected serum sodium depression. N Engl J Med. 1973;289(16):843-844. (Classic 1.6 mEq/L Na decrease per 100 mg/dL glucose rise above 100 mg/dL)
Hillier TA, Abbott RD, Barrett EJ. Hyponatremia: evaluating the correction factor for hyperglycemia. Am J Med. 1999;106(4):399-403. (Experimentally derived correction factor of 2.4 mEq/L per 100 mg/dL — found to be more accurate overall than 1.6; noted the relationship is nonlinear, with 1.6 performing adequately below glucose 400 mg/dL and a steeper ~4.0 factor fitting better above 400 mg/dL)
Holliday MA, Segar WE. The maintenance need for water in parenteral fluid therapy. Pediatrics. 1957;19(5):823-832. (Original 4-2-1 weight-based maintenance fluid formula)
Rout P, Afzal M. Hyponatremia. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2026 Jun 19. NBK470386. (First-24h hyponatremia correction ceiling: European Clinical Practice Guidelines set an upper limit of 10 mEq/L; the US expert panel is cited by a later compilation (Bello et al., PMC5407738) as limiting correction to 10–12 mEq/L per day for normal-risk patients and 8 mEq/L per day for high ODS-risk patients; traditional teaching cites 10-12 mEq/L/24h; total body water fraction of 0.6 for men/children, 0.5 for women/older adults)
Ball S. Hyponatremia. In: Feingold KR, Anawalt B, Blackman MR, et al., editors. Endotext [Internet]. South Dartmouth (MA): MDText.com; 2018 Jun 6. NBK279136. (First-24h ceiling 10 mmol/L with a pragmatic target of 6-8 mmol/L; after the first 24 hours, ceiling of no more than 8 mmol/L per subsequent 24h period — the two-tier ceiling used in the Hyponatremia tab is sourced to this chapter)
Sonani B, Al-Dhahir MA. Hypernatremia. StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; updated 2023 Aug 24. NBK441960. (Hypernatremia correction ceiling of 10-12 mEq/L/24h, confirming the Kidney Int Rep/Cureus sourcing below; free water deficit total body water fraction of 0.6 men / 0.5 women with no age adjustment stated — a simpler split than the Hyponatremia StatPearls chapter above; both are cited rather than silently resolving the inconsistency)
AlShanableh Z, Woodall A, Chisdak M, et al. Plasma Sodium Correction Rates in Patients with Severe Hyponatremia Treated with Hypertonic Saline with and without Proactive Desmopressin. Kidney360. 2025;6(9):1462-1471. (Desmopressin dosing observed in practice ~1.6-2 mcg every 6-8 hours; this paper's own study defined "overcorrection" as >8 mEq/L/24h as its research methodology, which is not the same as a guideline ceiling for every 24h window — see the note below)
Phekoo A, Sparks MA. Use of the Desmopressin Clamp in Hyponatremia: Smooth Sailing or Turbulent Waters? Kidney360. 2025;6(9):1430-1432. (Editorial reviewing proactive vs. reactive/rescue desmopressin use; rescue strategy is desmopressin plus a hypotonic fluid such as D5W after overcorrection has already occurred, aiming to relower plasma sodium back below the correction limit; also reviews recent evidence — Seethapathy et al., Ayus et al. meta-analysis — questioning whether the ODS risk from rapid correction alone is overstated relative to other risk factors)
Wang X, Chen X, Zhang L. Correction of extreme hypernatremia in acute kidney injury. Kidney Int Rep. 2017;2:1232-1236, as cited in: Alrashidi FS. Severe Hypernatremia During Continuous Hemofiltration in an End-Stage Renal Disease Patient: A Case Report and Updated Review. Cureus. 2025. (Hypernatremia correction generally should not exceed 10–12 mmol/L per 24 hours — independently confirmed by the StatPearls Hypernatremia chapter above)
Adrogué HJ, Madias NE. Hyponatremia. N Engl J Med. 2000;342(21):1581-1589. (Origin of the infusate formula used in the 3% Saline Infusion tab: predicted rise per liter of infusate = [Infusate Na − Serum Na] / [Total Body Water + 1]. This paper is paywalled and was not read directly — the formula and the 513 mEq/L value for 3% NaCl were independently confirmed by recomputing a worked example from the open-access case report below, which matched almost exactly)
Kawasaki RJ, et al. Refractory SIAD Triggered by Herpes Zoster Ophthalmicus: Impact of Postherpetic Neuralgia on Hyponatremia Duration and the Role of Tolvaptan. Intern Med. 2025 (online ahead of print). (Open-access worked example: 57.1 kg man, serum Na 116 mEq/L, predicted ~11.2 mEq/L rise per liter of 3% saline via the Adrogue-Madias formula — matches this tool's independent recalculation of 11.26 mEq/L. Also documents a predicted 2.24 mEq/L rise from a 200 mL bolus that produced only a 1 mEq/L actual rise due to increased urinary sodium loss — the basis for this tool's "recheck frequently" warning)
Dutta DK, Joshi A, Sharma M. Safety of Rapid Intermittent Bolus versus Slow Continuous Infusion of Hypertonic Saline for Managing Symptomatic Severe Hyponatremia: A Systematic Review and Meta-analysis. Ann Afr Med. 2025;24(2):431-437. Open access. (3 studies, 290 patients — both bolus and continuous infusion of 3% saline found safe and effective for severe symptomatic hyponatremia, with no significant difference in overcorrection risk; continuous infusion showed a nonsignificant trend toward shorter hospital stay. Source of the bolus-vs-infusion equivalence claim in the Bolus Protocol card above)
Spasovski G. Hyponatraemia-treatment standard 2024. Nephrol Dial Transplant. 2024;39(10):1583-1592. (Same lead author as the 2014 European Clinical Practice Guideline referenced below — this is the most current single-author treatment standard identified for hyponatremia, published 2024 with an erratum as recently as 2026, suggesting active ongoing revision. Paywalled [Oxford Academic] with no free full text found in this environment; not read directly. Its existence is disclosed here so that institutions with access can check it against the StatPearls/Endotext-sourced ceilings this tool currently uses)
Palmer BF, Clegg DJ. Hyperkalemia treatment standard. Nephrol Dial Transplant. 2024;39(7):1097-1104. (Current nephrology consensus for the Hyperkalemia Management tab: severity tiers 5.5-5.9/6.0-6.4/≥6.5 mEq/L; ECG is unreliable and must not be used to defer treatment at K⁺ >6.0 mEq/L; treatment sequencing of calcium → insulin/dextrose → albuterol → bicarbonate only if acidotic → binders → dialysis)
LaRue HA, Peksa GD, Shah SC. A Comparison of Insulin Doses for the Treatment of Hyperkalemia in Patients with Renal Insufficiency. Pharmacotherapy. 2017;37(12):1516-1522. PMID 28976587. (5-unit vs. 10-unit regular insulin: equivalent K⁺ reduction, significantly less hypoglycemia with 5 units — basis for the insulin dose shown in the Hyperkalemia tab)
FDA prescribing information: Calcium Gluconate Injection (DailyMed); Calcium Chloride Injection 10% (accessdata 021117s025, 2023 — specifies slow infusion via central/deep vein only, not peripheral bolus); Veltassa (patiromer, accessdata 205739Orig1s038, 2023); Lokelma (sodium zirconium cyclosilicate, accessdata 207078s000). (Source of the calcium route caution, and the potassium-binder onset-of-action figures — both binder labels explicitly state they are not for emergency treatment of life-threatening hyperkalemia)
FDA Drug Safety Communication, 2009 (Kayexalate/sodium polystyrene sulfonate label, accessdata 011287s023): serious WARNINGS AND PRECAUTIONS (section 5.1) for intestinal/colonic necrosis, risk heightened with concurrent sorbitol — note the current SPS label carries no boxed warning, so this should not be cited as one. (Basis for the tool's caution against SPS for acute hyperkalemia management)
KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024. kdigo.org. (Corroborates the severity tiers and treatment sequencing above via its own potassium-management content; primarily framed around chronic/RAAS-inhibitor-associated hyperkalemia rather than acute emergency sequencing)
FDA prescribing information: Potassium Chloride for Injection Concentrate (Pfizer/accessdata.fda.gov). (Source of the KCl limits in the K/Mg/Phosphate/Ca tab, read directly on DailyMed (Fresenius concentrate, setid bf8e8ac7-e6a8-4571-a0ea-7bcab89290f6): potassium above 2.5 mEq/L — up to 10 mEq/hour and up to 40 mEq/L, 24-hour total 200 mEq; urgent treatment (potassium below 2 mEq/L with ECG changes and/or paralysis) — up to 40 mEq/hour with continuous cardiac monitoring, up to 400 mEq in 24 hours. Premixed KCl label (ICU Medical, setid eb56a807-ea94-4edb-9811-a04b19568468): 300 and 400 mEq/L concentrations exclusively via the central route. The common peripheral/central institutional split is not in these labels and is disclosed in-app as institutional practice, not an ISMP-numbered standard.)
FDA prescribing information: Magnesium Sulfate Injection USP 50% (Hospira), DailyMed, rev. Aug 2021. (Dilute to ≤20% before IV use; max IV push rate ≤150 mg/min; the label’s 1–2 g/hour statement is in its pre-eclampsia/eclampsia dosing section, not a hypomagnesemia regimen)
FDA prescribing information: Calcium Gluconate Injection, DailyMed, rev. Nov 2023. (Bolus dilution 10-50 mg/mL, continuous-infusion dilution 5.8-10 mg/mL, max rate 200 mg/min adult / 100 mg/min pediatric/neonatal — used for both the routine hypocalcemia repletion dose in this tab and cross-referenced from the Hyperkalemia tab's calcium gluconate rec)
FDA prescribing information: Potassium Phosphates Injection, accessdata.fda.gov, 2024 revision. (Peripheral rate ≈6.8 mmol phosphorus/hr [≈10 mEq potassium/hr], max single/initial dose 45 mmol phosphorus)
ISMP List of High-Alert Medications in Acute Care Settings, January 2024. ismp.org. (Confirms KCl, IV magnesium, and IV phosphate salts as ISMP-designated high-alert medications; does not itself publish the specific peripheral/central mEq-per-100-mL numbers commonly taught — disclosed as a gap rather than misattributed)
Bello A, et al. Diagnosis and Treatment of Hyponatremia: Compilation of the Guidelines. Open access, PMC5407738. (Cross-source compilation of the 2013 US expert panel [Verbalis et al.] and 2014 European Clinical Practice Guideline [Spasovski et al.] — source of the Urine Na <30 mEq/L cutoff for identifying hypo-/hypervolemic hyponatremia, and the fluid-restriction thresholds [<1 L/day general, <500 mL/day if urine:serum electrolyte ratio >1] used in the Hyponatremia Diagnostic Workup tab)
"Hyponatremia" and "Syndrome of Inappropriate Antidiuretic Hormone Secretion." StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. NBK470386, NBK507777. (SIADH diagnostic criteria and cause list, primary polydipsia/low-solute-intake/hypothyroidism/secondary adrenal insufficiency differentiation)
FDA prescribing information: SAMSCA (tolvaptan), DailyMed. (Boxed warning: hospital-only initiation/re-initiation with close Na monitoring. Label cautions read directly on DailyMed: avoid use with hypertonic saline (W&P 5.4); avoid fluid restriction during the first 24 hours; liver-injury and 30-day limit and avoidance in underlying liver disease are label warnings, not part of the boxed warning — basis for the tolvaptan cautions in the Hyponatremia Diagnostic Workup tab)
Verbalis JG, Goldsmith SR, Greenberg A, et al. Diagnosis, Evaluation, and Treatment of Hyponatremia: Expert Panel Recommendations. Am J Med. 2013;126(10 Suppl 1):S1-42. Paywalled, not read directly in this environment — cited via the Bello et al. compilation above and secondary summaries; independent verification recommended if your institution has access.
Spasovski G, Vanholder R, Allolio B, et al. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrol Dial Transplant. 2014;29(Suppl 2):i1-i39. Paywalled, not read directly in this environment — same disclosure as above.
"Hypernatremia." StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing. NBK441960. (Urine osmolality-based diagnostic framework, central/nephrogenic DI causes, hypotonic fluid loss and sodium-gain etiologies used in the Hypernatremia Diagnostic Workup tab)
Desmopressin Nasal Spray, Summary of Product Characteristics. UK Electronic Medicines Compendium (EMC). (DDAVP challenge test protocol — timing of fluid restriction and urine osmolality measurements — and FDA prescribing information for the 10-40 mcg/day central DI treatment dose)
Akkara S, et al. Redefining Diagnostic Cut-Offs for the Indirect Water Deprivation Test. Clin Endocrinol. 2024. Open access, PMC11694560. (Proposed a refined ≥54% urine osmolality rise threshold for central DI in a small cohort — basis for this tool's disclosure that the classic >50%/<15% cutoffs vary across sources rather than being a single fixed number)
Fenske W, et al. A Copeptin-Based Approach in the Diagnosis of Diabetes Insipidus. N Engl J Med. 2018;379:428-439. Winzeler B, et al. Arginine-stimulated copeptin measurements in the differential diagnosis of diabetes insipidus. Lancet. 2019;394(10198):587-595. (Basis for this tool's note that copeptin-based testing is displacing the classic water-deprivation/desmopressin test as the reference standard where available; identified via search, not independently read in full text this session)

Disclosure (Hyperkalemia Management tab, added 2026-10-02): the digoxin caution quotes the calcium gluconate injection label (sections 5.1 and 7.1) and the DIGIFAB label, and the renal-impairment hypoglycemia line quotes the regular insulin label (section 8.6), all read on DailyMed on 2026-10-01 (primary_verified); the succinylcholine, triamterene-hydrochlorothiazide, amiloride, spironolactone, trimethoprim-sulfamethoxazole and heparin lines are from their current labels (primary_verified; amiloride, triamterene-hydrochlorothiazide and spironolactone are contraindicated in hyperkalemia; the heparin, tacrolimus and ACE-inhibitor lines are monitoring warnings, not contraindications). The digoxin-calcium statement that more recent human data show no worse outcomes, the 3 × 1 g calcium gluconate (or 1 g calcium chloride) equivalence, and the confirm-the-result and rebound-timing statements are from the KDIGO conference summary on acute hyperkalemia (Lindner G et al., Eur J Emerg Med 2020, open access; read in full; guideline_verified as an international KDIGO consensus summary, not a US society guideline; its thresholds are described as opinion-based). The 'ongoing potassium load' escalation is a clinical-judgment rule: the UK Kidney Association guideline (non_us_only; read in full) says moderate hyperkalemia at risk of further rise (for example oliguria or rhabdomyolysis) needs senior assessment and continuous ECG monitoring, but no US society text read here sets a threshold, and raising a potassium of 5.5–5.9 to the urgent tier is this tool's own extension (secondary_only). UpToDate could not be read (source_inaccessible: no content returned without a subscription). Pediatric dosing and a rhabdomyolysis, tumor lysis, DKA or burn-specific treatment protocol are not provided. The adults-only banner is a scope statement. The severity tiers, calcium/insulin/albuterol/bicarbonate sequencing, and binder onset-of-action figures above are sourced directly to Palmer & Clegg 2024 and current FDA labels (see reference list). One specific detail — whether to withhold the dextrose bolus and give insulin alone when baseline glucose is ≥250 mg/dL — came from secondary clinical-guide sources during development, not an independently confirmed primary source; the tool discloses this inline when that branch is shown and defers to institutional protocol. The 10-20 mg albuterol dose range is well-corroborated, but exact onset/peak-effect timing was intentionally left out of this tool's output rather than stated with false precision.

Disclosure (Hyponatremia & Hypernatremia Diagnostic Workup tabs): the two 2013/2014 primary hyponatremia guidelines (Verbalis et al., Spasovski et al.) are paywalled and were not read directly in this environment — the urine Na/osmolality cutoffs and fluid-restriction thresholds in the Hyponatremia Diagnostic Workup tab instead rest on a cross-source compilation review (Bello et al., PMC5407738) plus StatPearls, both freely accessible and cross-checked against each other. The exact SIADH urine-sodium cutoff (cited here as >30 mEq/L) varies between >30 and >40 mEq/L across secondary sources — disclosed in-app rather than presented as a single precise number. For the Hypernatremia Diagnostic Workup tab, the classic DDAVP-challenge cutoffs (>50% central DI, <15% nephrogenic DI) are long-standing teaching but a 2024 study proposed a different threshold in a small cohort, and copeptin-based testing is emerging as a more accurate alternative reference standard — both disclosed in-app. Neither workup tab is a substitute for endocrinology/nephrology consultation, especially for ambiguous/partial results.

Disclosure & revision note (K/Mg/Phosphate/Ca tab — pharmacist-workflow pass): a new Calcium section and concentration/rate-limit advisories were added for KCl, MgSO₄, potassium phosphate, and calcium gluconate — the specific IV verification checks (max peripheral/central concentration, max infusion rate) a hospital pharmacist actually checks against, which this tab previously lacked. An initial research pass assumed these peripheral-vs-central concentration splits would be found in a specific ISMP guidance document; direct verification found no such current, freely-accessible ISMP document with these exact numbers, so the split is now correctly attributed to common institutional/nursing-reference practice layered on top of the FDA label figures, rather than misattributed to ISMP (the KCl description was later corrected against the labels themselves — the labels carry a 40 mEq/L concentration figure and a 400 mEq urgent 24-hour maximum, and the premix label requires central administration for 300–400 mEq/L) — see the reference list for the FDA labels this section is sourced to directly.

Revision note (bolus protocol, most recent audit): the 3% Saline tab previously offered only a continuous-infusion (Adrogué-Madias) calculator, with the guideline-preferred bolus approach for severe symptomatic hyponatremia mentioned only as a passive text note. Because guidelines specifically favor 100 mL boluses over a calculated infusion for severe symptoms (seizures, obtundation, delirium) — and a 2025 meta-analysis independently confirmed both approaches are similarly safe — the bolus protocol was promoted to its own interactive calculator, placed first in the tab, with the continuous-infusion calculator now explicitly scoped to mild-to-moderate symptoms or ongoing correction.

Revision note (two-tier ceiling, earlier audit): an earlier version of the Hyponatremia tab used a single flat 8 mEq/L/24h ceiling for every 24-hour window, sourced only to the "overcorrection" definition used in the AlShanableh et al. 2025 study's own methodology. Cross-checking against the StatPearls and Endotext chapters above (both current, freely accessible, and independent of each other) found this was too strict for the first 24 hours specifically — the actual guideline-anchored ceiling for the first 24h is 10 mEq/L (European CPG), with a 6-8 mEq/L pragmatic target, and the 8 mEq/L ceiling applies to every 24h period after the first. The tool now reflects this two-tier structure. The two core hyponatremia expert guidelines themselves (Verbalis JG et al., Am J Med. 2013;126(10 Suppl 1):S1-42; Spasovski G et al., Nephrol Dial Transplant. 2014;29(Suppl 2):i1-i39) remain paywalled and could not be accessed in full text in this environment — the StatPearls and Endotext chapters are themselves secondary sources that summarize those guidelines, not the guidelines directly. If your institution has access to either original guideline (or the 2024 update above), independent verification against the full text is still worthwhile.

Clinical Disclaimer: ElectrolyteRx is a reference and verification aid for licensed healthcare professionals. It is not autonomous clinical software and does not replace clinical judgment, patient-specific assessment, institutional protocol, or — for sodium correction specifically — frequent laboratory monitoring and nephrology/endocrinology input for severe or symptomatic derangements.