Body temperatures vary slightly from person to person and at different times of day. The average temperature has traditionally been defined as 98.6 F (37 C). A temperature taken using a mouth thermometer (oral temperature) that's 100 F (37.8 C) or higher is generally considered to be a fever. Depending on what's causing a fever, other fever signs and symptoms may include: 
Sweating
Chills and shivering
Headache
Muscle aches
Loss of appetite
Irritability
Dehydration
General weakness
 Taking a temperature To take a temperature, you can choose from several types of thermometers, including oral, rectal, ear (tympanic) and forehead (temporal artery) thermometers. Oral and rectal thermometers generally provide the most accurate measurement of core body temperature. Ear or forehead thermometers, although convenient, provide less accurate temperature measurements. In infants, a rectal temperature, if doable, is somewhat more accurate. When reporting a temperature to your health care provider, give both the reading and the type of thermometer used.