Electrolyte Repletion — Med-Peds Resources

Safety scope: The doses below are general adult inpatient starting suggestions, not a replacement order set. Confirm the exact product, concentration, route, access, kidney function, monitoring, and repeat-lab timing against the current institutional protocol before administration (Kardalas 2018, PMID 29540487; Rosner 2023, PMID 36872194; Netzer 2025, PMID 41146174).

These ranges do not apply to children, pregnancy-specific indications, cardiac arrest, torsades de pointes, diabetic ketoacidosis, refeeding syndrome, tumor lysis syndrome, dialysis prescriptions, or other condition-specific pathways.

Adult inpatient decision guide

Hypokalemia

Mild, 3.0 to 3.4 mEq/L: If the patient is asymptomatic and can use the enteral route, a published adult review suggests potassium chloride 72 mmol by mouth per day in divided doses, with daily potassium measurement and dose adjustment (Kardalas 2018, PMID 29540487).
Moderate, 2.5 to 2.9 mEq/L: If there are no major symptoms and the enteral route is available, the same review suggests potassium chloride 96 mmol by mouth per day in divided doses, with daily potassium measurement and dose adjustment (Kardalas 2018, PMID 29540487).
Severe, below 2.5 mEq/L, symptomatic, or unable to take enteral therapy: Use IV potassium chloride under a monitored institutional pathway. A usual adult rate is 10 mEq per hour; 20 mEq per hour is a commonly cited upper rate that requires continuous ECG monitoring and frequent potassium reassessment (Kardalas 2018, PMID 29540487; Asmar 2012, PMID 22901631).
Kidney impairment: Reduce the starting dose or rate and reassess more frequently. One kidney-focused review suggests reducing IV rates by 50% to 80% when estimated GFR is below 30 mL/min/1.73 m², with potassium checks every 2 to 4 hours during active IV replacement (Asmar 2012, PMID 22901631).
Practical estimate: A 1 mEq/L serum potassium decrease often corresponds to a total-body deficit of roughly 200 to 400 mEq, but redistribution and ongoing losses can make this substantially wrong. In an ICU cohort, 20 to 80 mEq IV produced highly variable mean increases, so predicted response never replaces serial measurement (Kardalas 2018, PMID 29540487; Frenkel 2021, PMID 34063164).
Check magnesium and correct a concurrent deficiency because magnesium deficiency can make potassium replacement refractory (Kardalas 2018, PMID 29540487).
Concentrated potassium chloride must be diluted for IV infusion. Direct injection can be fatal, and renal insufficiency increases the risk of life-threatening hyperkalemia. Use a pharmacy-approved product and local concentration and access limits (Kardalas 2018, PMID 29540487; current US product label).

Hypomagnesemia

Mild and asymptomatic: Prefer oral replacement when the gastrointestinal tract is usable. A recent review suggests 200 to 400 mg elemental magnesium per day in divided doses, titrated to serum response and gastrointestinal tolerance (Floris 2025, PMID 40868117).
Severe, below 1 mg/dL, or symptomatic: A recent review suggests magnesium sulfate 1 to 2 g IV over 15 minutes, followed when needed by 4 to 8 g over 12 to 24 hours, with continuous cardiac monitoring and serial magnesium, potassium, and calcium measurements (Floris 2025, PMID 40868117).
Kidney impairment: Reduced clearance increases the risk of accumulation and toxicity, so use a lower dose and more frequent clinical and serum magnesium monitoring under the institutional pathway (Rosner 2023, PMID 36872194; current US product label).
Practical estimate: In 25,637 critically ill adults, each 1 g IV magnesium sulfate dose was associated with a median serum magnesium increase of 0.15 mg/dL, with an interquartile range of 0.05 to 0.25 mg/dL. The response was larger at lower baseline magnesium and with reduced kidney function, so this is an estimate, not a dosing equation (Said 2026, PMID 42266166).

Hypophosphatemia

Mild, moderate, or chronic: Prefer oral phosphate when the enteral route is usable. Select the formulation and dose using symptoms, severity, anticipated duration, kidney function, volume status, calcium, potassium, and acid-base status (Felsenfeld 2012, PMID 22863286; Netzer 2025, PMID 41146174).
Acute severe or symptomatic: The current systematic review found commonly recommended IV doses of 0.3 to 0.6 mmol/kg per day infused over 4 to 12 hours, with follow-up laboratory testing after 6 to 24 hours. These ranges are based largely on case reports and expert opinion, not comparative trials (Netzer 2025, PMID 41146174).
Salt and monitoring: Choose sodium phosphate or potassium phosphate by the patient’s sodium and potassium status, count the accompanying electrolyte load, and use a pharmacy-approved diluted product. IV phosphate can cause hypocalcemia and arrhythmias; monitor phosphate, calcium, potassium, sodium, and kidney function (Felsenfeld 2012, PMID 22863286; Netzer 2025, PMID 41146174; current US product label).

Hypocalcemia

Severe, below 1.9 mmol/L, or symptomatic acute hypocalcemia: The Society for Endocrinology adult guidance recommends 10 to 20 mL of 10% calcium gluconate diluted in 50 to 100 mL of 5% dextrose over 10 minutes with ECG monitoring, repeated until symptoms improve (Turner 2019, PMID 32022081).
If ongoing IV replacement is needed: The same guidance suggests diluting 100 mL of 10% calcium gluconate in 1 L of normal saline or 5% dextrose, starting at 50 to 100 mL per hour, and titrating to calcium level and symptoms while treating the cause (Turner 2019, PMID 32022081).
Product rule: In that regimen, 10 mL of 10% calcium gluconate contains about 2.2 mmol elemental calcium. Calcium chloride products and concentrations vary and calcium chloride should be given through central venous access because it is more irritating to veins (Turner 2019, PMID 32022081; current US product label).

Pediatric patients

Do not use the adult section as a pediatric order guide. For infants and children, use a pediatric-specific institutional pathway and pediatric pharmacy review. A PubMed-indexed pediatric emergency review separately covers the evaluation and management of potassium, calcium, magnesium, and phosphorus abnormalities in ill children (Conway 2023, PMID 36689544).

Evidence limits

No single current US society guideline supplies a universal replacement schedule across potassium, magnesium, phosphate, and calcium. The magnesium review reports a lack of clear data on optimal management, while the current phosphate systematic review identifies heterogeneous recommendations and gaps in dosing and monitoring evidence (Rosner 2023, PMID 36872194; Netzer 2025, PMID 41146174). The numeric ranges above are therefore general adult starting suggestions that require patient-specific adjustment and local protocol verification. Evidence and product labels were rechecked on 2026-08-04.