How long does it take for a child to get the results of a trace element test? The time varies according to the hospital and the test method. Trace element is mainly to check the intake of calcium, iron, zinc, selenium, copper, magnesium and other trace elements in the body, fast time can be the same day out of the results, slow time may take 3-5 days, usually in about 3 days. If the test is done through blood, it will take a little longer. If the result of trace element test cannot be used as the basis of clinical diagnosis, but only as a reference, the result can be available in a few hours or on the same day, so the time is not equal.