Work out free water deficit instantly with clear inputs, formula shown and shareable results.
Estimates the water needed to bring sodium back to 140 mmol/L, using total body water scaled from body weight.
Free water deficit
Deficit (L) = total body water x (measured Na / 140 - 1); TBW = weight x factor
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
No. Insensible and urinary losses must be added to the calculated deficit.
Usually no faster than 0.5 mmol/L per hour, or about 10 to 12 mmol/L in 24 hours.