Fever is a common symptom of a cold or flu-like infection. The function of fever is to support the body's defence processes. By raising the body temperature, the viral invaders in the body are weakened or killed. A fever is defined as a body temperature above 38° Celsius. Up to a temperature of 38°C, it is referred to as an elevated temperature. The normal body temperature is between 36.5 and 37°. The temperature can be measured under the tongue, in the armpits or rectally.