Apolipoprotein A1
The main structural protein of HDL particles.
| Typical reference range (male) | above 94 mg/dL |
| Typical reference range (female) | above 101 mg/dL |
Ranges vary by laboratory, method, age and sex: always use the range printed on your own report. Why labs differ.
What it measures
ApoA1 is produced by the liver and intestine and forms the backbone of HDL. It activates the enzyme LCAT, which allows HDL to pick up cholesterol from cells and transport it back to the liver.
Why it matters
ApoA1 reflects HDL particle quantity and function. The ApoB/ApoA1 ratio is a strong predictor of heart attack risk in large studies such as INTERHEART.
What a high result can mean
Higher values are generally favorable and accompany high HDL. Estrogen, exercise and moderate alcohol raise ApoA1.
What a low result can mean
Low ApoA1 parallels low HDL-C and is associated with insulin resistance, smoking, obesity and higher cardiovascular risk. Rare genetic deficiencies cause very low levels.
What affects the result
Fasting not required. Lifestyle factors that raise HDL raise ApoA1. Interpret with HDL-C and ApoB, or as the ApoB/ApoA1 ratio.
Units and conversion
Usually reported in mg/dL.
- From g/L: multiply by 100 to get mg/dL
- From mg/L: multiply by 0.1 to get mg/dL
Also called on lab reports
Apolipoprotein A-1, Apolipoprotein A-I, ApoA1, Apo A1, Apo A-1, ApoA-I, Apo A-I
Related tests: Lipids & Cardiovascular Risk
This page is educational and does not replace advice from a healthcare professional.