ApoA-I (Apolipoprotein A-I)

Apolipoprotein A-I (ApoA-I) is the main protein of 'good' HDL cholesterol. Your liver and gut make it, and it makes up about 70% of HDL's protein. It switches on an enzyme (LCAT) that drives 'reverse cholesterol transport', carrying cholesterol from your tissues back to the liver. Labs measure it by immunoassay, calibrated to a WHO/IFCC standard. Typical ranges are 110 to 180 mg/dL in men and 120 to 200 in women. It shines in one big study. In INTERHEART (12,461 cases and 14,637 controls across 52 countries), the ApoB/ApoA-I ratio was the single strongest lipid predictor of a first heart attack (odds ratio about 3.25, top vs bottom fifth). That beat the usual LDL-C/HDL-C ratio. Watch the confounders, though. Infection and inflammation drop it 20 to 30%. Pregnancy and oral estrogen raise it. Severe liver disease and rare ApoA-I mutations (Tangier disease, ApoA-I Milano) also shift it.

Last reviewed: June 22, 2026

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