Total serum cholesterol is the sum of cholesterol contained in all lipoproteins in the blood, including free cholesterol and cholesteryl esters. The range of the test varies from hospital to hospital due to different kits and instruments, but generally the normal range of total cholesterol is 3-5.2 mmol/L. The level of total cholesterol is also influenced by various factors such as age, diet, gender, and genetics. Elevated total cholesterol can be seen in hereditary hypercholesterolemia, nephrotic syndrome, biliary obstructive disease, hypothyroidism, etc. In contrast, a decrease in total cholesterol is mainly seen in chronic wasting states of malignant tumors, hyperthyroidism, anemia, severe infections, and intestinal absorption disorders. Total cholesterol of 5.5 mmol/L is mildly elevated, and if there are no clinical symptoms or organic diseases, it is most likely caused by the long-term consumption of high cholesterol foods. If you have low thyroid function, you should consider taking oral levothyroxine sodium tablets. If you have biliary obstruction, you should remove the obstruction in time, such as removing stones, removing tumors, or putting stents. If there is biliary obstruction, the obstruction should be removed promptly, such as removing stones, removing tumors, putting stents, etc., mainly to treat the primary disease.