Fasting insulin of 40 pmol/L (electrochemiluminescence immunoassay) is normal and not serious, while 40 U/L (chemiluminescence immunoassay) is on the high side and more serious. The range of reference values may vary from hospital to hospital. Normal fasting insulin values: 4.0-15.6 U/L (chemiluminescence immunoassay); 17.8-173.0 pmol/L (electrochemiluminescence immunoassay). Plasma insulin assay reflects the function of pancreatic β-cells. Insulin release test can measure plasma insulin level, which is an important method to know whether there is any disorder in the secretion function of pancreatic β-cells, the number of β-cells and the presence of insulin resistance. It is recommended to consult your doctor for the results of fasting insulin test.