Definition of Temperature measurement:

Temperature measurement is a method to take a person's temperature and determine whether it is within a normal range. A high temperature is a fever.

How the test is performed:

In the past, a glass thermometer filled with mercury was used to measure body temperature. However, the American Academy of Pediatrics (AAP) recommends against using mercury thermometers because the glass can break, and mercury is poisonous.

Electronic thermometers are most commonly used and recommended. The temperature is displayed on a digital readout. Follow the directions that come with the thermometer. Electronic probe thermometers can be placed in the mouth, rectum, or armpit.

Plastic strip thermometers change color to indicate the temperature. This method is the least accurate. Place the strip on the forehead and read it after 1 minute. Read it while the strip is in place. Plastic strip thermometers for the mouth are also available.

Always clean the thermometer before using. You can use cool, soapy water or rubbing alcohol. If you are using a glass thermometer, grip the end opposite the bulb and shake the thermometer downwards until it reads 95°F or less.

You can measure the temperature on three body locations:

• Mouth -- place the thermometer under the tongue and close the mouth. Breathe through the nose, and use the lips to hold the thermometer tightly in place. Leave the thermometer in the mouth for 3 minutes or until the device beeps.

• Rectum -- this method is for infants and small children who are not able to hold a thermometer safely in their mouths. Place petroleum jelly on the bulb of a rectal thermometer. Place the small child face down on a flat surface or lap. Spread the buttocks and insert the bulb end of the thermometer about 1/2 to 1 inch into the anal canal. Be careful not to insert the thermometer too far. Prevent the child from struggling, since this can accidentally push the thermometer in further. Remove the thermometer after 3 minutes or when the device beeps.

• Armpit -- place the thermometer in the armpit, with the arm pressed against the body for 5 minutes before reading. This is the least accurate method for using a glass thermometer.

Electronic ear thermometers are common and convenient, but some users report that the results are less consistent than probe thermometers.

Digital thermometers have easy-to-read displays. To read a glass thermometer, gripping the end opposite the bulb so that the numbers are facing you. Roll the thermometer back and forth between your fingers until you see a silver or red reflection in the column. Compare the end of the column with the degree marking in the lines on the thermometer.

How to prepare for the test:

Wait at least 1 hour after vigorous exercise or a hot bath before measuring body temperature. Wait for 20 to 30 minutes after smoking, eating, or drinking a hot or cold liquid.

How the test will feel:

There is very little discomfort.

Why the test is performed:

The measurement of body temperature determines whether a person has a fever. It may be helpful in monitoring to see if a person is ill or whether a treatment is working -- especially in antibiotic treatment of infections.