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Sodium Deficit Calculator

Free-water-based sodium deficit for hyponatremia.

Compute the sodium deficit in mmol needed to correct hyponatremia using TBW · (target_Na − current_Na). Total body water uses Watson coefficients (0.6 male, 0.5 female).

Priya Venkatesan By Priya Venkatesan
Published Last reviewed 1 min read

Inputs

kg
mmol/L
mmol/L

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Deficit (mmol) = TBW · (target_Na − current_Na). TBW = weight_kg · 0.6 (male) or 0.5 (female).

In depth

Compute the sodium deficit in mmol needed to correct hyponatremia using TBW · (target_Na − current_Na). Total body water uses Watson coefficients (0.6 male, 0.5 female).