What is body temperature?
Body temperature is a
measure of the body's ability to generate and get rid of heat. The body is very
good at keeping its temperature within a narrow, safe range in spite of large
variations in temperatures outside the body.
When you are too hot,
the blood vessels in your skin expand (dilate) to carry the excess heat to your
skin's surface. You may begin to sweat, and as the sweat evaporates, it helps
cool your body. When you are too cold, your blood vessels narrow (contract) so
that blood flow to your skin is reduced to conserve body heat. You may start
shivering, which is an involuntary, rapid contraction of the muscles. This
extra muscle activity helps generate more heat. Under normal conditions, this
keeps your body temperature within a narrow, safe range.
Where is body temperature measured?
temperature can be measured in many locations on your body. The mouth, ear,
armpit, and rectum are the most commonly used places. Temperature can also be
measured on your forehead.
What are Fahrenheit and Celsius?
Thermometers are calibrated in either degrees
Fahrenheit (°F) or degrees Celsius (°C), depending on the custom of the region.
Temperatures in the United States are often measured in degrees Fahrenheit, but
the standard in most other countries is degrees Celsius.
What is normal body temperature?
Most people think
of a "normal" body temperature as an oral temperature of
98.6°F (37°C). This is an
average of normal body temperatures. Your temperature may actually be 1°F
(0.6°C) or more above or below
98.6°F (37°C). Also, your
normal body temperature changes by as much as 1°F (0.6°C) throughout the day,
depending on how active you are and the time of day. Body temperature is very
sensitive to hormone levels and may be higher or lower when a woman is
ovulating or having her menstrual period.
rectal or ear (tympanic membrane) temperature reading
is slightly higher than an oral temperature reading. A
temperature taken in the armpit is slightly lower than an oral
temperature reading. The most accurate way to measure body temperature is to take a rectal temperature.
What is a fever?
In most adults, an oral
temperature above 100°F (37.8°C) or a rectal or ear temperature above
101°F (38.3°C) is considered a
fever. A child has a fever when his or her rectal temperature is
100.4°F (38°C) or
What can cause a fever?
A fever may occur as a
- Infection. This is the most common cause of a
fever. Infections may affect the whole body or a specific body part (localized
- Medicines, such as
antihistamines, and many others. These are called drug
fevers. Some medicines, such as antibiotics, raise the body temperature
directly. Other medicines interfere with the body's ability to readjust its temperature
when other factors cause the temperature to rise.
- Severe trauma or
injury, such as a
heat exhaustion or
heatstroke, or burns.
- Other medical
conditions, such as arthritis,
hyperthyroidism, and even some cancers, such as
Hodgkin's lymphoma, and liver and
Can a low body temperature be dangerous?