Obtaining an accurate measurement of your child's temperature requires some practice. If you have questions about this procedure, ask a physician or nurse to demonstrate how it's done and then to observe you doing the same.

Where to Take the Temperature

• Rectal temperatures are the most accurate. Oral or eardrum temperatures are also accurate if done properly. Axillary (armpit) temperatures are the least accurate but are better than no measurement.

• For a child younger than 5 years old, a rectal temperature is preferred. Axillary (armpit) temperature is adequate for screening if it is taken correctly. If your infant is less than 90 days old (3 months old) and axilliary temperature is over 99.0°F (37.2°C), check it by taking the rectal temperature. The reason we need a rectal temperature taken for young infants is that if they have a true fever, they need to be evaluated immediately.

• For a child 5 years old or older, take the temperature orally (by mouth).

Taking Rectal Temperatures

• Have your child lie stomach down on your lap.

• Before you insert the thermometer, apply some petroleum jelly to the end of the thermometer and to the opening of the anus.

Insert the thermometer into the rectum about 1 inch. During the first 6 months of life, gently insert the rectal thermometer ¼ to ½ inch (inserting until the silver tip disappears is about ½ inch). Never try to force it past any resistance. (Reason: it could cause perforation of the bowel.).

• Hold your child still while the thermometer is in.

• Leave the thermometer in your child's rectum for 2 minutes.

Taking Axilliary (Armpit) Temperatures

• Place the tip of the thermometer in a dry armpit.

• Close the armpit by holding the elbow against the chest for 4 to 5 minutes. You may mill detecting a fever if the thermometer is removed before 4 minutes.

• If you're uncertain about the result, check it with a rectal temperature.

Taking Oral Temperatures

• Be sure your child has not taken a cold or hot drink within the last 30 minutes.

• If using a glass thermometer, shake it until the mercury line is below 98.6°F (37°C).

• Place the tip of the thermometer under one side of the tongue and toward the back. An accurate temperature depends on proper placement. Ask a physician or nurse to show you where it should go.

• Have your child hold it in place with the lips and fingers (not the teeth) and breath through the nose, keeping the mouth closed.

• Leave it inside for 3 minutes.

• If your child can't keep his or her mouth closed because of nose blockage, suction out the nose.

Reading a Glass Thermometer. Find where the mercury line ends by rotating the thermometer until you can see the mercury.

Types of Thermometers

Glass (with Mercury) Thermometers. Glass thermometers are hard to read for many people but are the least expensive ($5.00). Glass thermometers come in two forms, oral with a thin tip and rectal with a rounder tip. This difference is not too important. If necessary, a rectal thermometer can be used in the mouth and an oral thermometer can e used in the rectum, as long as the thermometer is cleaned with rubbing alcohol and you are extra careful with rectal insertion. Note: Because glass thermometers contain mercury, they are not the recommended standard.

Digital Thermometers. Digital thermometers record temperatures with a heat sensor and run on a button battery. They measure quickly, usually in less than 30 seconds. The temperature is displayed in numbers on a small screen. The same thermometer can be used to take both rectal and oral temperatures. Buy one for your family; they cost about $10.00.

Ear Thermometers. Many hospitals and medical offices now take your child's temperature using an infrared thermometer that reads the temperature of the eardrum. In general, the eardrum temperature provides a measurement that is an accurate as the rectal temperature. The outstanding advantage of this instrument is that it measures temperatures in less than 2 seconds. It also requires no cooperation by the child and causes no discomfort (the thermometer is placed at the ear's opening). An ear thermometer for home use is available, but it's expensive ($60.00).

Conversion of Degrees
Fahrenheit ( F ) to Degrees
Centigrade ( C )

96.8°F = 36.0°C
98.6°F = 37.0°C
99.5°F = 37.5°C
100.0°F = 37.8°C
100.4°F = 38.0°C
101.0°F = 38.3°C
102.0°F = 38.9°C
103.0°F = 39.5°C
104.0°F = 40.0°C
105.0°F = 40.6°C
106.0°F = 41.1°C
107.0°F = 41.7°C

Adapted from Instructions for Pediatric Patients, 2nd Edition, 1999 by WB Saunders Company.
Written by Barton D. Schmitt, MD, pediatrician and author of Your Child's Health, Bantam Books, a book for parents.