Free Water Deficit – Hypernatremia Calculator
This calculator helps determine the free water deficit in patients with hypernatremia based on their total body water (TBW) and serum sodium levels. It is useful for healthcare professionals managing dehydration and electrolyte imbalances. By selecting the patient type and entering their weight and sodium values, the tool calculates how much free water is needed to correct sodium concentration.
Free Water Deficit – Hypernatremia
Free Water Deficit Formula
Where:
- TBW is Total Body Water (estimated from weight and patient type)
- Current Na is the current serum sodium concentration (mEq/L)
- Desired Na is the target serum sodium concentration, typically around 140 mEq/L
The Free Water Deficit is used to estimate how much water is needed to correct elevated sodium levels in cases of hypernatremia. Total Body Water (TBW) is calculated based on the patient’s age, sex, and weight—commonly using correction factors (e.g., 0.6 for adult males). This calculator simplifies the process for clinical use. For instance, a 70 kg adult male with a sodium level of 155 mEq/L and a target of 140 mEq/L would have a water deficit of approximately 7.5 liters.