Rectal temperature

Illustration showing how to insert a rectal thermometer

A rectal thermometer is the most accurate way to take a temperature. It is recommended for children younger than age 6 or for anyone who cannot hold an oral thermometer in the mouth.

To take a rectal temperature:

  1. Apply a lubricant jelly or petroleum jelly, such as Vaseline, on the bulb of the thermometer, so that you can insert it easily.
  2. When measuring the temperature of babies or small children, turn the child face down on your lap or on a flat covered or padded surface, such as a bed. Choose a quiet place so that the child won't be distracted or move around too much.
  3. Spread the child's buttocks with one hand and gently insert the bulb end of the rectal thermometer about 0.5 in. (1.3 cm) to 1 in. (2.5 cm) into the anal canal with your other hand. Don't force it into the rectum. Hold the thermometer in place with two fingers close to the anal opening (not near the end of the thermometer).
  4. Leave the thermometer in place for the required amount of time, usually a minute. Some digital thermometers give a series of short beeps when the reading is done. Time yourself with a watch or clock.
  5. Remove the thermometer and read it. A rectal temperature reading may be as much as 1°F (0.6°C) higher than an oral temperature reading.
  6. Clean a digital thermometer with cool, soapy water, and rinse it off before putting it away.
  7. After a thermometer has been used to take a rectal temperature, do not use it to take an oral temperature.

Last Updated: February 20, 2009

Medical Review: Kathleen Romito, MD - Family Medicine & E. Gregory Thompson, MD - Internal Medicine

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