Fasting basal plasma insulin is 35-145 pmol/L (5-20 mU/L) in normal people, with slight fluctuations in reference values in different hospitals. Insulin is a protein hormone secreted by the β-cells of the pancreatic islets and is the only hormone in the body that lowers blood glucose. After 75g of anhydrous glucose is taken orally, the plasma insulin level rises to a peak in about 30-60 minutes, and most of them will return to the basal level in 3-4 hours. Plasma insulin measurement is commonly used in clinical practice to reflect the function of pancreatic islet β-cells. Plasma insulin levels are measured at the same time as the OGTT, i.e., insulin release test, to find out whether there is any impairment of the secretory function of pancreatic β-cells, the number of β-cells, and whether there is any insulin resistance. The value of insulin can reflect the condition of the body to a certain extent. If there is any abnormality in the value of insulin, it is recommended to consult the doctor in time and under the guidance of the doctor.