Anion Gap Calculator

By CalculatorBolt Team | Published: Jan 15, 2025 | Updated: Jan 15, 2025 | Reviewed by: Health/Medical Editor

Calculate the serum anion gap from Na, K, Cl, and HCO3 values. Use mmol/L or mEq/L, optional albumin correction, and see reference ranges and interpretation. Informational only—consult a healthcare professional.

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Reference Ranges

Category Range (mmol/L or mEq/L)
Normal 8 – 16
High > 16
Low < 8

Ranges may vary by laboratory

Calculate Anion Gap

Normal range: 135-145 mmol/L
Normal range: 3.5-5.0 mmol/L
Normal range: 96-106 mmol/L
Normal range: 22-28 mmol/L

How it Works

Anion Gap = Na+ + K+ – Cl- – HCO3-. If albumin correction is used, we add 2.5 × (Reference Albumin – Measured Albumin). Normal range is roughly 8–16 (mmol/L or mEq/L).

Formulas:

Anion Gap = Na+ + K+ – Cl- – HCO3-
Corrected AG = AG + 2.5 × (Reference Albumin – Measured Albumin)

Inputs Explained

  • Lab Values: Na, K, Cl, HCO3 from blood test results
  • Units: mmol/L or mEq/L (numerically equivalent for these ions)
  • Albumin Correction: Optional; used in hypoalbuminemic states
  • Rounding: Choose precision for results

Example

Lab Values:

  • Na: 140 mmol/L
  • K: 4.0 mmol/L
  • Cl: 100 mmol/L
  • HCO3: 24 mmol/L

Calculation:

AG = 140 + 4 – 100 – 24 = 20 mmol/L

Interpretation: High (> 16)

Tips & Notes

  • Albumin correction is used in hypoalbuminemic states; enable if needed.
  • Reference ranges may vary slightly by laboratory.
  • High anion gap suggests conditions like ketoacidosis, lactic acidosis, renal failure.
  • Low anion gap is less common; may occur in hypoalbuminemia or lab error.
  • Clinical context is essential for interpretation.

FAQs

Generally 8–16 mmol/L or mEq/L. Use the calculator to see your result and interpretation based on your lab values.

In patients with low albumin (hypoalbuminemia); enable the toggle and enter albumin values. The correction accounts for the effect of low albumin on anion gap.

No. It's an informational tool. Consult a qualified healthcare professional for medical diagnosis and treatment.

No. Everything runs in your browser. Use Export or Share Link to save your configuration locally. No server-side storage.

Common causes include diabetic ketoacidosis, lactic acidosis, renal failure, toxic ingestions (methanol, ethylene glycol), and salicylate poisoning. Always consult a healthcare provider for interpretation.

⚠️ Disclaimer

Informational estimate only. Anion gap interpretation depends on clinical context. This tool is not a substitute for professional medical advice, diagnosis, or treatment. Consult a qualified healthcare professional for medical concerns.

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