Anion Gap Calculator
Calculate the serum anion gap and delta-delta ratio for metabolic acidosis workup and acid-base disorder classification.
Medical Disclaimer
This calculator is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making decisions about your health. Never disregard professional medical advice or delay seeking it because of results from this tool.
Inputs
Normal Na⁺: 136–145 mEq/L; hyponatremia: <136; hypernatremia: >145 mEq/L
Normal Cl⁻: 98–106 mEq/L; hyperchloremia >106 mEq/L may indicate normal-AG acidosis
Normal HCO₃⁻: 22–29 mEq/L; metabolic acidosis: <22; metabolic alkalosis: >29 mEq/L
Normal albumin: 3.5–5.0 g/dL; corrected AG = measured AG + 2.5 × (4.0 − albumin)
Results
Anion Gap
12mEq/L
Corrected AG (Albumin)
12mEq/L
How to Use This Calculator
- Enter serum sodium (Na⁺), chloride (Cl⁻), and bicarbonate (HCO₃⁻) in mEq/L.
- Set albumin level (g/dL) for albumin-corrected anion gap calculation.
- Review Anion Gap and corrected anion gap — normal is 8–12 mEq/L (or 3–11 with albumin correction).
- Elevated AG > 12 triggers MUDPILES differential (methanol, uremia, DKA, etc.).
How the result changes with Sodium (Na⁺)
| Sodium (Na⁺) | Anion Gap | Corrected AG (Albumin) |
|---|---|---|
| 110 | -18mEq/L | -18mEq/L |
| 135 | 7mEq/L | 7mEq/L |
| 165 | 37mEq/L | 37mEq/L |
| 190 | 62mEq/L | 62mEq/L |
What each input means
- Sodium (Na⁺)
- Serum sodium concentration in mEq/L. AG = Na⁺ − (Cl⁻ + HCO₃⁻). Normal range 136–145 mEq/L.
- Chloride (Cl⁻)
- Serum chloride concentration in mEq/L. Normal range 98–106 mEq/L. Hyperchloremia (>106) can be seen with normal anion gap metabolic acidosis.
- Bicarbonate (HCO₃⁻)
- Serum bicarbonate (CO₂) concentration in mEq/L. Normal range 22–29 mEq/L. Low HCO₃⁻ (<22) indicates metabolic acidosis.
- Albumin
- Serum albumin for corrected anion gap calculation. Hypoalbuminemia reduces the AG by ~2.5 mEq/L per 1 g/dL fall in albumin. Normal range 3.5–5.0 g/dL.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersSodium (Na⁺) = 140, Chloride (Cl⁻) = 104, Bicarbonate (HCO₃⁻) = 24, Albumin = 4 = 4 input(s) provided
- Calculate Anion GapAnion Gap12 = 12
- Calculate Corrected AGCorrected AG12 = 12
- Calculate Delta-Delta RatioDelta-Delta Ratio0 = 0
- Calculate ClassificationClassification1 = 1
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