Low HDL cholesterol is a manifestation of dyslipidemia, the causes of which are mostly related to diseases and medications. HDL cholesterol is the group of lipoproteins with the highest particle density in the serum, and its increased level facilitates the removal of cholesterol from peripheral tissues, thus preventing atherosclerosis from occurring. It is an anti-atherosclerotic factor, and is an important indicator for recognizing the risk of early atherosclerosis. A lower HDL means a greater susceptibility to cardiovascular disease. Low HDL cholesterol is common in diseases such as atherosclerosis, cirrhosis of the liver, diabetes mellitus, nephrotic syndrome, etc. It is also possible that it may be reduced after the application of androgens or drugs such as beta-blockers and progesterone. If it is caused by taking certain medications, it is necessary to consult the doctor to reduce the amount of medication cautiously. If the patient has low HDL cholesterol, the cause of the decrease needs to be further clarified, and targeted treatment should be taken according to the doctor’s instructions.