Blood tests are not required after a child has a fever, and most of the causes of fever in children are due to infections of various pathogenic bacteria. For example, if a child is infected with bacteria, viruses, or Mycoplasma pneumoniae, Chlamydia, etc., the pathogenic bacteria will cause an increase in the number of endothermic sources, which will lead to an upward shift in the child’s thermoregulation point, which will cause the child’s fever. At this time, blood tests can be performed to determine whether the fever is viral or bacterial in nature, and it is not necessary to test the blood on an empty stomach. It is not necessary to test the blood of the child on an empty stomach. Fasting blood tests are used only for lipids and fasting blood sugar.