Trace element test is not necessary to fasting, the main check is the content of trace elements in the body, but all the tests try to keep in the fasting state, can rule out the external factors caused by inaccurate test results. Trace element tests are as follows: 1) DNA extraction from body hair. 2) Finger tip blood test or venous blood test, which is best done on an empty stomach for more accurate results. The method of extracting DNA from body hair can be done without fasting. The trace elements of the human body mainly include zinc, selenium, copper, magnesium, etc., each of which has a positive effect on the growth and development of the human body.