<P> Sleep disturbances also affect temperatures . Normally, body temperature drops significantly at a person's normal bedtime and throughout the night . Short - term sleep deprivation produces a higher temperature at night than normal, but long - term sleep deprivation appears to reduce temperatures . Insomnia and poor sleep quality are associated with smaller and later drops in body temperature . Similarly, waking up unusually early, sleeping in, jet lag and changes to shift work schedules may affect body temperature . </P> <P> A temperature setpoint is the level at which the body attempts to maintain its temperature . When the setpoint is raised, the result is a fever . Most fevers are caused by infectious disease and can be lowered, if desired, with antipyretic medications . </P> <P> An early morning temperature higher than 37.2 ° C (99.0 ° F) or a late afternoon temperature higher than 37.7 ° C (99.9 ° F) is normally considered a fever, assuming that the temperature is elevated due to a change in the hypothalamus's setpoint . Lower thresholds are sometimes appropriate for elderly people . The normal daily temperature variation is typically 0.5 ° C (0.90 ° F), but can be greater among people recovering from a fever . </P> <P> An organism at optimum temperature is considered afebrile or apyrexic, meaning "without fever". If temperature is raised, but the setpoint is not raised, then the result is hyperthermia . </P>

What is the normal temperature of human blood