Free Water Deficit Calculator for Hypernatremia Management

Calculate Free Water Deficit

Please enter a valid weight.
Please select a patient type.
Please enter current serum sodium.
Please enter desired serum sodium.

Use this Free Water Deficit Calculator to precisely determine the amount of free water required to correct hypernatremia. Essential for clinicians managing patients with elevated serum sodium, it aids in planning fluid therapy for effective dehydration reversal and preventing complications.

Formula:

The Free Water Deficit (FWD) is calculated using the following formula:

FWD = TBW × ((Serum Na / Desired Na) - 1)

Where:

  • FWD = Free Water Deficit (Liters)
  • TBW = Total Body Water (Liters)
    • For Adult Males: TBW ≈ 0.60 × Weight (kg)
    • For Adult Females: TBW ≈ 0.50 × Weight (kg)
    • For Children: TBW ≈ 0.60 × Weight (kg)
  • Serum Na = Current Serum Sodium Concentration (mEq/L)
  • Desired Na = Desired Serum Sodium Concentration (mEq/L)

Note: This calculator is intended for hypernatremia (high sodium levels) correction.

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