Acid-BaseUpdated 2025-12-24Medically Reviewed
Anion Gap
Everything you need to know about Anion Gap levels, including what normal ranges look like and what abnormal results might indicate.
Standard Reference Range
Unit: mmol/LMale Reference Range
8–16 (lab-dependent) mmol/L
Female Reference Range
8–16 (lab-dependent) mmol/L
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Reference ranges may vary slightly between laboratories. Always consult your doctor for interpretation.
What is the Anion Gap?
The anion gap is a calculated value (Na - Cl - HCO₃⁻) that estimates unmeasured acids/anions in blood.
Key Takeaway
High anion gap metabolic acidosis points to added acids (lactate, ketones, toxins); normal gap acidosis points to bicarbonate loss.
Why is this test performed?
- Classify metabolic acidosis causes
- Detect lactic acidosis, ketoacidosis, or toxic alcohols
- Monitor renal failure or severe infections
Interpreting Your Results
- High Gap (＞16): Lactic acidosis, ketoacidosis, renal failure, toxins (methanol, ethylene glycol, salicylates)
- Normal Gap (＜12) with Low HCO₃⁻: Bicarbonate loss (diarrhea, renal tubular acidosis)
Related Tests
- Sodium / Chloride / Bicarbonate / Potassium: Inputs and contributors
Decode your Anion Gap (AG) Results
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