Overview

A fever is a rise in body temperature. It's often a sign of infection. Fever itself most often is harmless and it may play a role in fighting infection. Most fevers don't need treatment.

The average body temperature is 98.6 Fahrenheit (37 Celsius). But typical body temperature can range between 97 F (36.1 C) and 99 F (37.2 C) or more. Your body temperature can vary by how active you are, your age or the time of day. Most often, older people have lower body temperatures than younger people have.

These thermometer readings are thought to be a fever:

• Rectal, ear or temporal artery temperature of 100.4 F (38 C) or higher.
• Oral temperature of 100.4 F (38 C) or higher.
• Armpit temperature of 99 F (37.2 C) or higher.