Sodium Deficit Calculator
Sodium deficit calculator estimates mEq of sodium needed to correct hyponatremia safely. The formula uses TBW (0.6 for males, 0.5 for females) multiplied by the target minus current sodium. Safe correction limits 8 to 10 mEq/L per 24 hours.
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Formula
How it works: Calculates the milliequivalents of sodium required to raise the serum concentration to a safer target.
Worked Example
Understanding Sodium Deficit in Hyponatremia
The sodium deficit formula calculates how many milliequivalents of sodium are needed to raise a patient's serum sodium from its current level to a safe target. This guides IV fluid selection and volume.
- Formula: Sodium Deficit (mEq) = TBW x (Target Na - Current Na), where TBW = 0.6 x weight for males, 0.5 for females
- Normal sodium range: 135 to 145 mEq/L; hyponatremia is below 135 mEq/L
- Safe correction rate: 8 to 10 mEq/L per 24 hours to avoid osmotic demyelination syndrome (ODS)
- 3% hypertonic saline contains 513 mEq Na per liter; 0.9% normal saline contains 154 mEq Na per liter
- Severe symptomatic hyponatremia (seizures, coma) may require initial rapid bolus of 100 mL 3% saline
This calculator is for educational purposes only. Hyponatremia management requires close monitoring of sodium levels and should always be guided by a qualified healthcare professional.
You can also calculate changes using our Fluid Deficit Calculator or Serum Osmolality Calculator.
Frequently Asked Questions
How quickly should sodium be corrected?
General guidelines recommend not exceeding a raise of 8 to 10 mEq/L in a 24-hour period to avoid osmotic demyelination syndrome (ODS). Some severe symptomatic cases may warrant faster initial correction.
What is osmotic demyelination syndrome?
ODS (formerly central pontine myelinolysis) is a serious neurological condition caused by overly rapid correction of chronic hyponatremia. It damages the myelin sheath of brain cells and can cause permanent disability.
Does this calculate IV fluid volume?
No. This calculates the total sodium deficit in mEq. You must then select the appropriate fluid (3% NaCl has 513 mEq/L, 0.9% NaCl has 154 mEq/L) and calculate the volume needed based on clinical protocols.
What is TBW in this formula?
Total Body Water (TBW) is typically weight x 0.6 for men and weight x 0.5 for women. For a 70 kg male, TBW is 42 liters.
When is hyponatremia considered severe?
Severe hyponatremia is generally defined as sodium below 120 mEq/L, or any level with neurological symptoms such as seizures, altered consciousness, or coma.
Is this calculator a substitute for medical advice?
No. This tool is for educational purposes only. Sodium correction is a high-risk intervention that should always be managed by a qualified healthcare professional with frequent laboratory monitoring.
How can I put this Sodium Deficit Calculator on my blog or website?
Yes, the Sodium Deficit Calculator is fully embeddable. Tap "Embed" above to configure appearance and copy the code. It is free to use, works on any platform (HTML, WordPress, CMS), and adjusts to any screen size automatically. Visit calculory.com/services/embed-calculators for the complete guide.
Medical Disclaimer
This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.
AI Assistant
Ask about this calculator
I can help you understand the sodium deficit calculator formula, interpret your results, and answer follow-up questions.
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Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.
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