The time it takes for the fever to go down after a fever-reducing injection varies from person to person, and it usually starts to go down in about half an hour after application. However, it may take 3-4 hours for the fever to subside completely. Depending on the degree of infection and the resistance of the patient, the time to reduce fever after antipyretic injection varies. Generally, the fever gradually subsides between half an hour and an hour after an adequate dose of antipyretic injection. If the fever cannot be reduced or if there is a re-increase in body temperature after the fever is reduced, the medicine can be used again after 4-6 hours. At the same time, the original disease should be actively searched for. If the fever is caused by bacterial infection, effective antibiotics should be selected for treatment according to the results of bacterial drug sensitivity test. In addition, a small number of patients may be due to lower resistance or more serious infections, may antipyretic injection effect is not good, 1-2 hours after the injection can gradually reduce fever. In addition, patients should strictly follow the doctor’s advice before the use of antipyretic injection, and after the injection, they should closely monitor the changes of the condition and actively treat the primary disease at the same time.