Hypernatremia Correction

All calculations should be independently verified prior to clinical use. These calculators are intended to supplement, not replace, clinical judgment.

Calculate the required infusate Na⁺ concentration to achieve a target serum Na⁺ correction of −10 mEq/L per day using the Adrogué–Madias formula, with maintenance fluid volume (Holliday-Segar) as the infusate volume.

Rate of correction. Hypernatremia should be corrected at a rate no faster than 10–12 mEq/L per day (approximately 0.5 mEq/L per hour). Overly rapid correction of chronic hypernatremia risks cerebral oedema. Serum Na⁺ should be rechecked every 4–6 hours and the infusate adjusted accordingly. This calculator uses a single-step approximation; recalculate frequently as Na⁺ changes.

Baseline weight kg

Total body water fraction L/kg

Serum Na⁺ mEq/L

Infusate volume mL/day

Total body water (TBW) L

Maintenance volume mL/day

Target ΔNa⁺ mEq/L per day

Target ΔNa⁺ per liter
−10 mEq/L per day ÷ infusate volume (L/day) mEq/L per L

Required infusate Na⁺ mEq/L

The Adrogué–Madias formula predicts the change in serum Na⁺ per liter of a given infusate:

ΔNa⁺ = Na⁺_infusate − Na⁺_serum TBW + 1

where TBW (total body water, in liters) = weight × TBW fraction. The default TBW fraction of 0.6 L/kg applies to children and adult males; 0.5 L/kg is appropriate for adult females and elderly patients; 0.45 L/kg for obese patients. The “+1” in the denominator accounts for the liter of infusate added to the body water.

To find the required infusate concentration that achieves a target ΔNa⁺ of −10 mEq/L per day, the formula is rearranged. The daily infusate volume is set to the Holliday-Segar maintenance volume (V, in L/day), giving a per-liter target of −10 ÷ V:

ΔNa⁺_per L = −10 V_maintenance

Na⁺_infusate = ΔNa⁺_per L × ( TBW + 1 ) + Na⁺_serum

The result is the Na⁺ concentration (in mEq/L) of the infusate that, when given at the maintenance rate over 24 hours, will lower serum Na⁺ by approximately 10 mEq/L. Select the closest available IV fluid from the table below and add KCl as needed. Recheck serum Na⁺ every 4–6 hours and recalculate.

This calculator applies to hypernatremia without concurrent dehydration. For hypernatremia with dehydration, use the Dehydration Correction Calculator first, then return here to manage any residual hypernatremia.

Available IV fluid reference (Na⁺ concentrations):

Solution	Na⁺ (mEq/L)
3% Saline	513
NS (0.9% Saline)	154
Lactated Ringer’s	130
½ NS (0.45% Saline)	77
⅓ NS (0.3% Saline)	51
¼ NS (0.22% Saline)	39
⅕ NS (0.2% Saline)	30
D5W / Sterile Water	0

References

Adrogué HJ, Madias NE. Hypernatremia. N Engl J Med. 2000;342(20):1493–1499. DOI: 10.1056/NEJM200005183422006.