Human Body Temperature

Human Body Temperature

Normal human body temperature, also known as normothermia or euthermia, depends upon the place in the body at which the measurement is made, and the time of day and level of activity of the person. Despite what many schoolchildren are taught, there is no single number that represents a normal or healthy temperature for all people under all circumstances using any place of measurement.

Different parts of the body have different temperatures. Rectal and vaginal measurements, or measurements taken directly inside the body cavity, are typically slightly higher than oral measurements, and oral measurements are somewhat higher than skin temperature. The commonly accepted average core body temperature (taken internally) is 37.0 °C (98.6 °F). The typical oral (under the tongue) measurement is slightly cooler, at 36.8° ± 0.4°C (98.2° ± 0.7°F), and temperatures taken in other places (such as under the arm or in the ear) produce different typical numbers. Although some people think of these numbers as representing the normal temperature, a wide range of temperatures has been found in healthy people.

In healthy adults, body temperature fluctuates about 0.5 °C (0.9 °F) throughout the day, with lower temperatures in the morning and higher temperatures in the late afternoon and evening, as the body's needs and activities change. The time of day and other circumstances also affect the body's temperature. The core body temperature of an individual tends to have the lowest value in the second half of the sleep cycle; the lowest point, called the nadir, is one of the primary markers for circadian rhythms. The body temperature also changes when a person is hungry, sleepy, or cold.