The normal body temperature has long been thought to be 37 degrees Celsius (98.6 degrees Fahrenheit), but there are several factors that affect body temperature. Normal body temperature varies by person and can also increase or decrease as a person ages, changes environment, changes diet or alters medication. Temperature readings can also vary slightly based on the method of temperature reading and the time of day that the person's temperature is taken.
The average human body temperature was determined to be 37 degrees Celsius (98.6 degrees Fahrenheit) by a study conducted in Germany. Body temperature can be measured using different devices placed against the mouth, nose, ear, armpit or rectum. The UK and the United States unit of measurement for temperature is degrees Fahrenheit, but almost every other country uses degrees Celsius.
What it means
Body temperature measures a person's ability to generate and eliminate heat. A healthy body eliminates excess heat through sweat and generates heat by making you shiver and constricting your blood vessels so that they stop giving off heat.
A fever is when a person's temperature rises over 37.8 degrees Celsius (100 degrees Fahrenheit). Fevers usually indicate that a person is taking medication or that they have an infection, a thyroid problem or another illness such as arthritis or cancer. These things raise a person's temperature because the body is trying to eliminate foreign subjects (such as a medication or infection) by releasing them through heat energy.
Temperatures drop for several different reasons, including shock, drug use, vitamin or mineral deficiency or severe infection. Temperatures occasionally drop as a result of extremely low external temperatures.
Body temperature varies from person to person based on each person's metabolism speed, medication and environment. Any temperature between 36.33 and 37.44 degrees Celcius (97.4 and 99.4 degrees Fahrenheit) is normal. To determine an individual person's body temperature, temperature should be taken several times over a period of several days and averaged together. Temperature is most accurate when taken orally with a digital thermometer when the person has not exercised within an hour, and when no caffeine or sugar has been ingested within an hour.
Variations throughout life
Body temperature in a person can vary throughout that person's life. Reasons for this include changes in thyroid or metabolism, drastic changes in environment or weight changes.