There are many clinical causes of fever, and when the human body has a fever that is significantly too high, it is possible to cause fainting. This is because when a person has a fever the body becomes in poor condition and also does not think about eating and drinking, it can cause a lack of blood volume in the body and a drop in blood pressure, which triggers ischemia and lack of oxygen in the brain, and fainting with fever can occur. If the body temperature is too high, there will also be convulsions and loss of consciousness. If you know you have a fever, you need to take timely fever reduction treatment. Body temperature below 38.5 degrees can be physically cooled. If the body temperature is higher than 38.5 degrees, timely antipyretic treatment needs to be given. You can take oral ibuprofen or acetaminophen to reduce fever, and then assist with physical cooling. If the fever does not go down all the time, you need to have a more complete examination to clarify the cause of the fever and then treat it symptomatically.