Anion Gap
Calculator

The anion gap is calculated from basic blood electrolytes (sodium minus the sum of chloride and bicarbonate) and represents the difference between routinely measured positive and negative ions in the blood. It's used as a diagnostic clue to help classify the underlying cause of metabolic acidosis.

The gap exists on paper because not all ions in the blood are routinely measured; unmeasured anions like albumin, phosphate, and sulfate account for the mathematical difference, not an actual imbalance of charge. Blood is always electrically neutral overall.

An elevated anion gap typically suggests the presence of unmeasured acids in the blood, commonly seen in conditions like diabetic ketoacidosis, lactic acidosis, kidney failure, or certain toxic ingestions. This makes it a useful first clue for narrowing down the cause of metabolic acidosis.

Since albumin itself is one of the major unmeasured anions contributing to the gap, low albumin levels (common in malnourished or critically ill patients) can mask a genuinely elevated anion gap by making the calculated value appear artificially normal. Some clinicians apply a correction factor for albumin when interpreting borderline results.

No, the anion gap is only meaningful in the context of other lab values, symptoms, and clinical history, and its interpretation requires medical training. This calculator is for reference and educational purposes, not self-diagnosis.