hdl-c refers to high-density lipoprotein cholesterol, and low levels are considered to be associated with atherosclerosis, diabetes mellitus, cirrhosis of the liver, hepatocellular carcinoma, and acute infections, etc. Consultation with a specialist is recommended. HDL cholesterol is mainly synthesized in the liver and small intestine, and has an anti-atherosclerotic effect. By measuring the HDL cholesterol level, we can indirectly know the level of HDL in the blood. An HDL cholesterol level greater than 1.04 mmol/L is considered an appropriate level, and a level less than or equal to 1.0 mmol/L is considered to be lowered. It has been found that serum HDL levels are negatively correlated with the development of coronary heart disease, i.e., low HDL cholesterol predisposes to the development of coronary heart disease. In contrast, if HDL-C is greater than 1.55 mmol/L is considered a protective factor against coronary heart disease. If HDL-C is low, it is recommended to check the cause of the problem in time and treat it actively.