Trace elements can be checked in two ways: hair test and blood test. The blood test is a common and routine method, which can be done by enzyme-linked immunoassay and chemiluminescence. After 12 hours of fasting, we need to take blood from the hospital in the morning to check the trace elements. If you eat staple food, the results will be inaccurate. In addition, hair can be used to test the trace elements of the human body, but it is believed that there is a certain degree of error in checking the trace elements through hair examination.