Albumin-corrected anion gap calculator: Figge 1998 formula

About this calculator

The calculator corrects the anion gap for hypoalbuminaemia. Albumin is the main negatively charged plasma protein; when it drops, the measured anion gap underestimates the true gap. Per Figge 1998: corrected AG = measured AG + 2.5 × (4.0 − albumin g/dL). Each 1 g/dL fall in albumin below the 4 g/dL reference understates the AG by about 2.5 mmol/L. Categories: <12 normal, 12–20 elevated, >20 wide. The correction matters most in sepsis, cirrhosis and AKI, where albumin can fall to 2–3 g/dL and the raw AG may look falsely normal. SEMI recommends the corrected AG for every ICU patient with hypoalbuminaemia.

Source

Figge J, Jabor A, Kazda A, Fencl V. Crit Care Med 1998;26(11):1807-10

Formula version: figge-1998-v1