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Estimates sodium deficit for hyponatremia correction planning. Helps determine the total amount of sodium needed to raise serum sodium to a target level.
Sodium Deficit = 0.6 * weight * (desiredNa - currentNa)
0 mmol
Interpret results together with the patient's clinical presentation.
Specialty
Internal MedicineCategory
Internal MedicineDifficulty
Basic
Estimated Time
30 seconds
Version
1.0
Last Updated
2026-08-06
Formula
Keywords
Normal Range
0 mmol
| Classification | Range |
|---|---|
Deficit below normal range | <-100 |
Normal (no deficit) | -100–0 |
Sodium deficit present | ≥0 |
Large sodium deficit | ≥500 |
Estimates the total sodium deficit to guide hyponatremia correction, helping clinicians plan replacement while avoiding over-correction.
The sodium deficit is calculated as 0.6 × weight × (target Na − current Na) using an estimated total body water of 0.6 × weight. Values are interpreted against the clinical urgency of correction rather than a fixed normal range.
Estimating the sodium deficit helps clinicians replace sodium methodically and avoid osmotic demyelination syndrome caused by over-rapid correction.
A 70 kg man with chronic hyponatremia has a serum sodium of 125 mmol/L; the goal is 135 mmol/L.
Inputs:
Sodium deficit = 0.6 × 70 × (135 − 125) = 420 mmol. Correct slowly, limiting the rise to 8–10 mmol/L in the first 24 hours.
For chronic hyponatremia, limit correction to 8–10 mmol/L in the first 24 hours and 18 mmol/L in 48 hours to reduce the risk of osmotic demyelination syndrome.
Total body water is approximately 60% of body weight in men and 50% in women. This calculator uses 0.6 × weight as a default estimate.
Estimating water replacement in hypernatremia.
Addresses hypernatremia, not hyponatremia.
Disclaimer: This calculator is intended for educational and clinical decision support purposes only. Sodium correction must be guided by frequent monitoring and institutional protocols.