Estimate the free-water deficit in hypernatraemia from sex, weight, current sodium, and a goal sodium.
| Deficit | – |
Use this calculator for the usual TBW × (Na ÷ goal − 1) sketch of free-water deficit. Total body water is taken as 0.6 × weight in men and 0.5 × weight in women. A negative result (current sodium already below the goal) is shown as 0. This is not a correction-rate protocol and it does not replace serial sodium checks.
Weight can be entered in kilograms (kg) or pounds (lb); the calculator converts to kilograms before the formula. The deficit is shown in litres (L) or gallons (gal).
Sex: Sets the 0.6 vs 0.5 TBW fraction.
Weight: Body weight, in kg or lb.
Current Na: Current serum sodium, in mmol/L.
Goal Na: Target sodium, often 140 mmol/L.
Deficit: Estimated free-water deficit.
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