Low ApoA1 is defined as a level of ApoA1 in the body below 1.2g/L and can be used to predict the risk of cardiovascular disease. ApoA1 is synthesized by the liver and small intestine, mainly in HDL, and plays an important role in cholesterol and lipoprotein metabolism. The normal range of ApoA1 is 1.2~1.96g/L, and the specific reference value varies according to the instrument used in each hospital, but the difference is not significant. Decreased ApoA1 is one of the best predictors of the risk of developing coronary artery disease because the level of ApoA1 is negatively correlated with the degree of coronary artery disease. However, reduced ApoA1 can also be seen in nephrotic syndrome, active hepatitis, liver parenchymal depletion, and diabetes mellitus, which are associated with diseases affecting lipoprotein metabolism. It is recommended to go to the hospital for further counseling.