Anion Gap Calculator
Anion gap with albumin correction and delta ratio.
Albumin is itself a major unmeasured anion, so a low level hides a raised gap.
Optional. Include it only if your laboratory reports the gap with potassium.
Albumin-corrected anion gap
12.0 mmol/L
Within reference range
A normal gap in acidosis usually points to gastrointestinal bicarbonate loss or renal tubular acidosis.
How the Anion Gap Calculator works
The anion gap is the difference between measured cations and anions, representing the unmeasured anions in plasma. Its main use is splitting metabolic acidosis into high-gap and normal-gap causes, which point to very different diagnoses.
Not medical advice. This calculator gives a general estimate, not medical advice. It cannot account for your individual health, medical history, or medication. Talk to a qualified healthcare professional before acting on any result.
Frequently asked questions
How is the anion gap calculated?
Sodium − (chloride + bicarbonate). Some laboratories include potassium: (sodium + potassium) − (chloride + bicarbonate), which raises the reference range by about 4 mmol/L. Know which convention your lab reports.
What is a normal anion gap?
Roughly 8-12 mmol/L without potassium, or 12-16 with it. The range has drifted down over the decades as chloride assays changed, so older textbook figures often read high.
Why correct the anion gap for albumin?
Albumin is itself a major unmeasured anion, so hypoalbuminaemia lowers the gap and can hide a genuine high-gap acidosis. The usual correction adds about 2.5 mmol/L for every 1 g/dL that albumin falls below 4.
What causes a high anion gap acidosis?
The classic mnemonic is GOLDMARK: glycols, oxoproline, L-lactate, D-lactate, methanol, aspirin, renal failure, ketoacidosis. Normal-gap acidosis usually points to gastrointestinal bicarbonate loss or renal tubular acidosis.