How long it takes for a child’s fever to go down after a fever-reducing injection depends on the condition of the disease and the degree of sensitivity to the fever-reducing medication. In most cases, after applying the injected fever-reducing medication, basically within 1-2 hours, the body temperature can be gradually reduced to normal, or the body temperature begins to appear to decline. If the child is infected with viruses or bacteria that are more virulent, or less sensitive to the effects of a particular antipyretic drug, there may not be a significant change in temperature 1-2 hours after the application of antipyretic drugs, in this case, it is not recommended to continue to use the same type of antipyretic drugs, and you should go to the hospital for medical treatment as soon as possible.