How does Hypoalbuminemia effect Anion Gap?

Albumin makes up a majority of the anion gap (unmeasured anion protein). Hence in states of low albumin, an anion gap acidosis can falsely appear as a non-anion gap acidosis.

WHY? The albumin will be low – lowering the baseline gap and require much more unmeasured anions to exceed the cutoff of 12.

RULE OF THUMB: For every drop of 10g/L in albumin, drop the anion gap cutoff by 2.5-3mmol. (i.e with an albumin of 30, the anion gap cutoff is now 9)


  1. Figge J, Jabor A, Kazda A, and Fencl V. Anion gap and hypoalbuminemia. Crit Care Med 1998 Nov; 26(11) 1807-10
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Dr. C Humphreys

Internal Medicine

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