There are two ways to test trace elements: one is to test the trace elements in hair; the other is to test the trace elements in blood. Most hospitals use the method of testing blood for trace elements, which does not require fasting, and the amount of blood collected and the way it is collected varies from one instrument to another. Trace elements usually include calcium, iron, zinc, magnesium, etc. Zinc deficiency can affect the child’s taste development and the development of the nervous system. When calcium is low, it can affect the health of the bones. When iron is deficient, it can easily lead to iron deficiency anemia and insufficient hemoglobin synthesis, so it is important to pay some attention to the testing of trace elements.