Currently, there are two methods used in hospitals to check for zinc: one is to use hair to test for zinc, which is called hair zinc; the other is called blood zinc, which is done by collecting blood. However, since both methods may be affected by the external environment, such as the contamination of the collection apparatus, and may produce certain errors, the most accurate criteria for determining zinc deficiency are the test results and clinical symptoms. The clinical manifestations of zinc deficiency are: 1. Loss of appetite. Children generally eat less, and some of them do not feel hungry and do not take the initiative to eat; 2. For example: bite nails, clothing, chew toys, hard objects, eat hair, confetti, raw rice, wall dust, dirt, sand and gravel, etc.; 3, not growing taller. For infants within one year of age, the parents’ observation is very important because they do not yet have the ability to express themselves. Children within one year of age is the first peak of height growth, each month will grow at least 2 ~ 3 cm, the first six months will even grow 4 ~ 5 cm per month, so parents can initially determine whether there is a zinc deficiency problem based on monitoring the child’s height; 4, slow hair growth. This is often overlooked by parents. For example, some children’s hair grows for most of the year without any care, which is most likely caused by zinc deficiency; 5, white spots on the nails, long barbs on the fingers, map tongue (irregular red and white graphics on the surface of the tongue); 6, hyperactivity, slow reaction, inattention, poor learning ability; 7, especially prone to viral infections. For example, frequent colds and fevers, recurrent respiratory infections such as tonsillitis, bronchitis, pneumonia, night sweats in bed, etc.; 8, recurrent mouth ulcers. However, a single symptom cannot be used as a criterion to determine whether a child is zinc deficient or not, and a comprehensive approach should be taken. For example, a poor appetite may not necessarily be a zinc deficiency, because such anorexia may also belong to anorexia nervosa. It is only when there are other symptoms that the child may be zinc deficient and should be examined by a hospital in time.