A fever, also referred to as pyrexia, is an elevation in the body temperature above the norm. This is broadly defined as oral temperature reading above 37.5 degrees Celsius (99 degrees Farenheit) and a core body temperature (rectally) above 38 degrees Celsius (100.4 degrees Farenheit).
Variations in temperature may occur depending on where the measurement is taken (oral, rectal, axilla). A fever should not be diagnosed by touching and estimating the skin temperature or the feeling of being ‘feverish’. The body temperature varies by a maximum of 0.6 degrees Celsius (adults) and 0.5 degrees Celsius (children) in the course of a day – the lowest temperatures are usually recorded in the morning and the highest by late afternoon.