💧 Free Water Deficit (Hypernatraemia)
UseGuide water replacement in hypernatraemia.
SourceAdrogué HJ, Madias NE. N Engl J Med 2000
This-shift next steps
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Methodology · worked example, guidelines & full notes
Add ongoing and insensible losses to the calculated deficit.
When to use
Guide water replacement in hypernatraemia.
How it works
Deficit = TBW × (Na/140 − 1), where TBW = body-water factor × weight (0.6 male, 0.5 female/elderly).
Key points
- Add ongoing and insensible losses to the calculated deficit.
- Correction rate recommendations vary between sources; follow your local protocol.
References
Worked calculation
The values below come from this tool's own example placeholders and are computed server-side with the formula shown on this page, so the arithmetic can be checked quickly. It demonstrates how to substitute values only — it is not clinical advice and not a real case.
| Weight | 70 kg |
|---|---|
| Current sodium | 160 mmol/L |
| Total body water factor | Adult female / elderly male (0.5) |
→Free water deficit5.0L
- Total body water：35.0 L
- Formula：TBW × (Na/140 − 1)
- Correction rate：Recommendations vary between sources; follow your local protocol and recheck sodium.
| Weight | 70 kg |
|---|---|
| Current sodium | 160 mmol/L |
| Total body water factor | Adult male (0.6) |
→Free water deficit6.0L
- Total body water：42.0 L
- Formula：TBW × (Na/140 − 1)
- Correction rate：Recommendations vary between sources; follow your local protocol and recheck sodium.
Verification & sources · governance
FAQ
Frequently asked questions
- What are the limits and cautions when using Free Water Deficit (Hypernatraemia)?
- For licensed clinicians and clinical researchers. Interpret results with history, investigations and local protocols; not a diagnosis or prescription, and not a substitute for multidisciplinary decision-making or local guidelines.
- Does Free Water Deficit (Hypernatraemia) upload patient data? Where is it calculated?
- Calculation runs locally in the browser; inputs and results are not uploaded. For licensed clinicians only; interpret with history, investigations and local protocols — not a diagnosis or prescription.
- How is Free Water Deficit (Hypernatraemia) calculated in practice? Can you show a worked example?
- Inputs: Weight 70 kg, Current sodium 160 mmol/L, Total body water factor Adult female / elderly male (0.5) → Result: Free water deficit 5.0 L（Total body water: 35.0 L, Formula: TBW × (Na/140 − 1), Correction rate: Recommendations vary between sources; follow your local protocol and recheck sodium.） Inputs: Weight 70 kg, Current sodium 160 mmol/L, Total body water factor Adult male (0.6) → Result: Free water deficit 6.0 L（Total body water: 42.0 L, Formula: TBW × (Na/140 − 1), Correction rate: Recommendations vary between sources; follow your local protocol and recheck sodium.）