Due to the large differences between individuals, there is no fastest way to reduce fever, for a high fever of 40 degrees fever usually include increased hydration, physical cooling and taking medication, etc., if the high fever persists should be timely medical treatment, to avoid delaying the condition. 1. Increase hydration: When the fever is 40 degrees, the patient’s body will lose a lot of water, and should drink more warm water in time to avoid the symptoms of electrolyte disorders due to dehydration. 2. Physical hypothermia: When the fever is 40 degrees, the initial treatment of physical hypothermia should be taken in time, such as ice packs and hot towels, including the face, neck, armpits, limbs, etc. If the effect is not good, you can use warm water to take a bath. 3. Taking medication: In addition to physical cooling and increased hydration, fever-reducing medications, such as ibuprofen granules and acetaminophen, should be taken in a timely manner under the guidance of a doctor. If the fever is caused by bacterial infection, it can be supplemented with medication such as Roxithromycin. If the symptoms are not relieved after taking the medicine, you should seek medical advice promptly.