LDL cholesterol 5.1 mmol/L is severe. LDL cholesterol, also known as LDL cholesterol, is synthesized in the liver. For healthy people, its normal value is less than 3.37 mmol/L. For patients with coronary heart disease and diabetes, it is recommended to stabilize below 1.82 mmol/L. Lower values may be caused by malnutrition, chronic anemia, and severe liver disease. High values may be caused by diet, nephrotic syndrome, and other factors. When the value is high, it can lead to lipid deposition and increase the risk of cardiovascular diseases, such as coronary heart disease and cerebral infarction. Patients with high LDL cholesterol should first adopt a healthy lifestyle, reduce the intake of saturated fatty acids and cholesterol, and increase the intake of fiber-rich foods. They need to be treated with statins, such as atorvastatin, and if statin treatment is not up to standard, or statin intolerance, ezetimibe can be added, and PSK9 inhibitors, such as aliskirenzumab or iloyuzumab, can also be chosen. The specific cause of the disease needs to go to the hospital for further examination, and then can be clarified, according to the doctor’s guidance for appropriate treatment.