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Body temperature is a measure of your body's ability to make and get rid of heat. The body is very good at keeping its temperature within a safe range, even when temperatures outside the body change a lot.
Your body temperature can be measured in many places on your body. The most common ones are the mouth, the ear, the armpit, and the rectum. Temperature can also be measured on your forehead.
Thermometers show body temperature in either degrees Fahrenheit (°F) or degrees Celsius (°C). In the United States, temperatures are often measured in degrees Fahrenheit. The standard in most other countries is degrees Celsius.
Most people think a normal body temperature is an oral temperature (by mouth) of 98.6°F (37°C). This is an average of normal body temperatures. Your normal temperature may actually be 1°F (0.6°C) or more above or below this. Also, your normal temperature changes by as much as 1°F (0.6°C) during the day, depending on how active you are and the time of day. Body temperature is very sensitive to hormone levels. So a woman's temperature may be higher or lower when she is ovulating or having her menstrual period.
A rectal or ear temperature reading will be a little higher than an oral reading. A temperature taken in the armpit will be a little lower than an oral reading. The most accurate way to measure temperature is to take a rectal reading.
In most adults, a fever is an oral temperature above 100.4°F (38°C) or a rectal or ear temperature above 101°F (38.3°C). A child has a fever when his or her rectal temperature is 100.4°F (38°C) or higher.
A fever may occur as a reaction to:
If a low body temperature is your only symptom, it is not something to worry about. If a low body temperature occurs with other symptoms, such as chills, shaking, breathing problems, or confusion, then this may be a sign of more serious illness.
Low body temperature usually happens from being out in cold weather. But it may also be caused by alcohol or drug use, going into shock, or certain disorders such as diabetes or low thyroid.
A low body temperature may occur with an infection. This is most common in newborns, older adults, or people who are frail. A very bad infection, such as sepsis, may also cause an abnormal low body temperature.
Heatstroke occurs when the body fails to control its own temperature and body temperature keeps rising. Symptoms of heatstroke include mental changes (such as confusion, delirium, or unconsciousness) and skin that is red, hot, and dry, even under the armpits.
Heatstroke can be deadly. It needs emergency medical treatment. It causes severe dehydration and can cause body organs to stop working.
There are two types of heatstroke.
Body temperature is measured to:
Take your temperature a few times when you are well. This will help you find out what is normal for you. Check your temperature in both the morning and evening. Body temperature can vary by as much as 1°F (0.6°C) during the day.
Before you take your temperature:
There are different types of thermometers.
Glass thermometers that contain mercury are not recommended. If you have a glass thermometer, contact your local health department to find out how to dispose of it safely. If you break a glass thermometer, call your local poison control center right away.
Before you take a temperature, read the instructions for how to use your type of thermometer. Some common ways to take a temperature are described below.
Oral (by mouth) is the most common method of taking a temperature. For you to get an accurate reading, the person must be able to breathe through his or her nose. If this is not possible, use the rectum, ear, or armpit to take the temperature.
This is the most accurate way to measure body temperature. It is recommended for babies, small children, and people who can't hold a thermometer safely in their mouths. It is also used when it is very important to get the most accurate reading.
Do not use a thermometer to take an oral temperature after it has been used to take a rectal temperature.
Taking a temperature in the armpit may not be as accurate as taking an oral or rectal temperature.
Ear thermometers may need to be cleaned before they are used.
Forehead thermometers are not as accurate as electronic and ear thermometers. If your baby is younger than age 3 months or your child's fever rises higher than 102°F (39°C), check the temperature again using a better method.
Pacifier thermometers are not as accurate as electronic and ear thermometers. If your baby is younger than age 3 months or your child's fever rises higher than 102°F (39°C), check the temperature again using a better method.
Taking an oral temperature causes only mild discomfort. You have to keep the thermometer under your tongue and hold it in place with your lips.
Taking a rectal temperature can cause a little discomfort, but it should not be painful.
Taking an ear temperature causes little or no discomfort. The probe is not inserted very far into the ear, and it gives a reading in only a few seconds.
Taking a temporal artery, forehead, or armpit temperature does not cause any discomfort.
There is very little chance of a problem from taking a temperature.
When taking a rectal temperature, do not push the thermometer in more than 0.5 in. (1.25 cm) to 1 in. (2.5 cm). Pushing it farther can be painful and may damage the rectum.
Body temperature is a measure of your body's ability to make and get rid of heat.
If you tell your doctor about your temperature reading, be sure to say where it was taken: on the forehead or in the mouth, rectum, armpit, or ear.
The average normal temperature is 98.6°F (37°C). But that may not be normal for you. Your temperature also changes during the day. It is usually lowest in the early morning. It may rise as much as 1°F (0.6°C) in the early evening. Your temperature may also rise by 1°F (0.6°C) or more if you exercise on a hot day.
A woman's body temperature often changes by 1°F (0.6°C) or more through her menstrual cycle. It peaks around the time she ovulates.
Oral, ear, rectal, or temporal artery temperature
A rectal or ear temperature of less than 97°F (36.1°C) is a low body temperature (hypothermia).
A temperature reading may not be accurate if:
To learn more about fever, see:
Other Works Consulted
Auwaerter PG (2007). Approach to the patient with fever. In LR Barker et al., eds., Principles of Ambulatory Medicine, 7th ed., pp. 457–465. Philadelphia: Lippincott Williams and Wilkins.
El-Radhi AS, Barry W (2006). Thermometry in paediatric practice. Archives of Disease in Childhood, 91(4): 351–356.
Current as of:
June 26, 2019
Author: Healthwise StaffMedical Review: Susan C. Kim MD - PediatricsAdam Husney MD - Family MedicineMartin J. Gabica MD - Family MedicineKathleen Romito MD - Family MedicineJohn Pope MD - PediatricsDavid Messenger MD
Current as of:
June 26, 2019
Medical Review:Susan C. Kim MD - Pediatrics & Adam Husney MD - Family Medicine & Martin J. Gabica MD - Family Medicine & Kathleen Romito MD - Family Medicine & John Pope MD - Pediatrics & David Messenger MD
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