🧪 Anion Gap Calculator
Calculate the serum anion gap, with optional albumin correction, to work up a metabolic acidosis.
Clinical takeaway
A high gap points to lactate, ketones, toxins or uraemia.
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When to use
Evaluate acid–base disorders; distinguish high- from normal-anion-gap acidosis.
How it works
AG = Na − (Cl + HCO₃); reference ~8–12 mmol/L. Corrected AG = AG + 2.5 × (4 − albumin g/dL).
Key points
- A high gap points to lactate, ketones, toxins or uraemia.
- Low albumin lowers the measured gap — always correct it.
- Reference range is laboratory-dependent.
References
Decision support for licensed clinicians only; not a substitute for clinical judgement, diagnosis or local protocols.
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.
| Sodium (Na⁺) | 140 mmol/L |
|---|---|
| Chloride (Cl⁻) | 104 mmol/L |
| Bicarbonate (HCO₃⁻) | 24 mmol/L |
| Albumin (optional) | 4.0 g/dL |
→Anion gap12.0mmol/L
- Formula：AG = Na − (Cl + HCO₃)
- Reference：8–12 mmol/L (lab-dependent)
- Albumin-corrected AG：12.0 mmol/L (+2.5 per 1 g/dL below 4)
Frequently asked questions
- What is Anion Gap Calculator?
- Calculate the serum anion gap, with optional albumin correction, to work up a metabolic acidosis.
- How is Anion Gap Calculator calculated? What is the core formula?
- AG = Na − (Cl + HCO₃); reference ~8–12 mmol/L. Corrected AG = AG + 2.5 × (4 − albumin g/dL).
- When is Anion Gap Calculator used?
- Evaluate acid–base disorders; distinguish high- from normal-anion-gap acidosis.
- What are the key clinical points for Anion Gap Calculator?
- A high gap points to lactate, ketones, toxins or uraemia. Low albumin lowers the measured gap — always correct it. Reference range is laboratory-dependent.
- What are the limits and cautions when using Anion Gap Calculator?
- 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.
- How is Anion Gap Calculator calculated in practice? Can you show a worked example?
- Inputs: Sodium (Na⁺) 140 mmol/L, Chloride (Cl⁻) 104 mmol/L, Bicarbonate (HCO₃⁻) 24 mmol/L, Albumin (optional) 4.0 g/dL → Result: Anion gap 12.0 mmol/L（Formula: AG = Na − (Cl + HCO₃), Reference: 8–12 mmol/L (lab-dependent), Albumin-corrected AG: 12.0 mmol/L (+2.5 per 1 g/dL below 4)）