Cholesterol 6.71mmol/L is not within the normal range and is abnormal. The normal range of serum total cholesterol should be less than 5.20 mmol/L. Therefore, cholesterol 6.71 mmol/L is above the upper limit of the normal range and is considered high cholesterol, which can increase the risk of cardiovascular diseases. High cholesterol may be associated with heredity, dietary preferences such as animal offal and fatty foods, lack of exercise, alcohol consumption, and stress. Hypercholesterolemia is an important risk factor for stroke, coronary heart disease and sudden cardiac death. Hypercholesterolemia can lead to angina pectoris, myocardial ischemia, cerebral infarction, cerebral softening and other diseases, and in severe cases, can cause acute myocardial infarction or even sudden death. Patients with cholesterol 6.71mmol/L should go to the hospital and be treated under doctor’s guidance.