CalculatorsKidneys and electrolytesAnion gap calculator
Anion gap calculator
Work out the gap from your metabolic panel, and correct it for albumin so a low albumin doesn't hide a raised gap.
10mEq/L
Usual
About 4 to 12 mEq/L is usual on modern analysers. Check the range on your own report.
See the working
Gap = Na − (Cl + HCO3) = 140.0 − (104.0 + 26.0) = 10.0What the gap is
Blood stays electrically balanced, but a standard panel only measures some of the charged particles. The gap is the difference between the main positive one, sodium, and the main negative ones, chloride and bicarbonate. It stands for everything not measured.
When acids build up in the blood, the gap rises. That's what makes it useful, especially next to a low bicarbonate.
Why albumin matters
Albumin is the biggest unmeasured negative charge. If it's low, the gap reads low, and can hide a real rise. Each 1 g/dL under 4 hides about 2.5 mEq/L. Add your albumin here, and the correction is done for you.
Questions
What's a normal anion gap?
About 4 to 12 mEq/L on modern analysers. Older references say 8 to 16, so use the range on your own report.
What raises it?
Lactic acid build-up, ketones, kidney failure and some poisonings are the classic causes. A small rise alone often means little.
What does a low gap mean?
Most often a low albumin or a lab variation. It's rarely serious on its own.
Should I worry about a high result?
With feeling unwell, fast breathing, or diabetes or kidney disease, get seen today. Otherwise raise it with your doctor, who may repeat the test.
Sources
Written by LifeFrom from the sources above, and not yet reviewed by a clinician. An estimate for your own understanding: it doesn't diagnose or treat anything, and it doesn't replace your doctor.
