There is no general rule that you can only take ibuprofen if you have a fever of 38.5°C. Ibuprofen is a non-steroidal anti-inflammatory drug with antipyretic and analgesic effects that can relieve mild to moderate headaches, as well as fevers caused by colds. A mouth temperature above 38°C in adults and 38.5°C in infants is usually referred to as moderate fever, and before that it is considered as hypothermia. Patients with low-grade fever may not experience significant headache, malaise, or nausea, and can be relieved with adequate rest and physical modalities such as ice packs to cool the body, wet ice towels, and warm water baths. Tuberculosis, urinary tract infections, bacterial infections and medications such as antibiotics can also cause hypothermia or prolonged hypothermia and require targeted treatment, so abuse of antipyretics is not recommended until the cause is clear. Ibuprofen has certain adverse effects, such as indigestion, nausea, vomiting, drowsiness, tinnitus, etc. Bone marrow suppression and even liver damage can occur if taken in large doses, so it is not recommended for patients to use the drug at will. After the body temperature exceeds 38.5℃, patients have already experienced obvious discomfort, such as severe headache, burning skin, loss of appetite and weakness, etc., they should use the medication under the guidance of doctors after promptly clarifying the cause. In addition to ibuprofen, acetaminophen is also a commonly used fever reducer. During fever, you should avoid smoking, drinking alcohol, staying up late, ensure sufficient rest, and enhance nutrition by eating a light and easily digestible diet with more fresh fruits and vegetables, as well as lean meat, eggs, milk, soy products and other foods with high protein content.