Normal body temperature traditionally is thought to be about 37 degrees Celsius (98.6 degrees Fahrenheit). This measurement, however, usually corresponds to temperature taken orally. Body temperature may vary according to where it is measured. Although measurements taken under the arm may not always be completely accurate, they can give you an approximate figure for determining whether or not you have fever.
Temperature taken under the arm usually is considered to be less accurate than most other body locations for measuring temperature. This measurement, also known as "axillary temperature," tends to be about half a degree to a degree below oral temperature. Therefore, normal axillary temperature would range between 36.4 degrees C and 527 degrees Celsius (97.6 degrees and 98.1 degrees Fahrenheit).
Other measurement sites
Rectal temperature is thought to be most accurate when determining actual body temperature for children. Normal range runs between 36 and 37.7 degrees Celsius (97 and 100 degrees Fahrenheit). Ear temperature (or "tympanic" temperature) also is very accurate in children and adults. 37.5 degrees Celsius (99.5 degrees Fahrenheit) is the normal temperature for this method. Measuring body temperature orally is perhaps the most traditional means of measurement. Although 37 degrees Celsius (98.6 degrees Fahrenheit) is the standard norm, healthy range can vary between 36.7 and 37.1 degrees Celsius (98.2 and 98.8 degrees Fahrenheit).
How to measure temperature in the armpit
Place a clean thermometer under the arm and place the arm back down on top of it snugly. If you are using a digital thermometer, it should beep when it is finished measuring. If you have a glass thermometer that uses alcohol or galinstan as its means of measurement, leave the thermometer under the arm for at least five minutes. Be careful to stay still when using a glass thermometer so that you don't cause it to break. It is recommended that glass thermometers containing mercury be thrown away, since the mercury is toxic to humans and animals.
Extra steps towards accuracy
Make sure your thermometer is clean. Wash it in slightly warm, soapy water before and after each use. If you have been exercising (or eating and/or drinking in the case of oral thermometers), wait at least 15 minutes before taking your temperature. When taking axillary temperature, use an electronic thermometer for the most accurate results. Read it as soon as it beeps, indicating that the measurement is complete.
Pros and cons
Measuring temperature under the arm has benefits and disadvantages. The obvious downside is that it is less accurate than other means of measurement. An advantage is that it is not very invasive. Many children have a hard time holding still for temperature measurement in other areas of the body, but they can tolerate having the thermometer at the armpit.