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Topic Overview
A fever is a high body temperature. Average normal body temperature is 98.6°F (37°C) orally. It usually varies during the day from a low of 97.4°F (36.33°C)in the morning to a high of 99.6°F (37.56°C) in the late afternoon. Exercising, wearing too many clothes, taking a hot bath, or being out in hot weather can cause an increase in your temperature.
Fever is the body's normal reaction to infection and other conditions, both minor and serious. Fever causes the immune system to increase the production of white blood cells and other substances that help fight infection.
Fever is a symptom, not a disease. Often the importance of a fever can only be determined when other symptoms are evaluated. A temperature of up to 102°F (38.89°C) can be helpful, because it helps the body react to an infection. Most healthy children and adults can tolerate a fever as high as 103°F (39.44°C) to 104°F (40°C) for short periods of time without problems.
- Are in good health without any medical problems.
- Don't have other significant symptoms with the fever.
- Are taking in enough food and fluids.
- Are urinating normal amounts.
- Seem to be improving.
Rectal temperatures are the most accurate, especially in young children. Older children and adults usually take oral temperatures. Temperatures in this topic are oral temperatures. Ear probe thermometers are used often but are generally less accurate. Temperature color strips on the skin are not accurate and should not be used to measure a fever. For information on how to take an accurate temperature, see the topic Body Temperature in Related Information.
For specific fever guidelines for children age 3 and younger, see the topic Fever, Age 3 and Younger, in Related Information.
