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How to Take a Rectal Temperature

Reviewed by: Melanie L. Pitone, MD
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How Do I Take a Rectal Temperature?

The best way to take a temperature in infants and young children is by taking a rectal temperature. Don't worry — it's a simple and safe process.

First:

  • If your baby has had a bath or has been under blankets or in multiple layers (or swaddled, if an infant), wait about 20–30 minutes to take the temperature. 
  • Use a digital thermometer. Don’t use a glass thermometer, as these aren’t safe.
  • Wash the end of the thermometer with soap and water and rinse with water.
  • Moisten the tip of the thermometer with a lubricant, such as petroleum jelly.

Then, place your child:

  • belly-down across your lap or on a firm, flat surface and keep your palm along the lower back
    or
  • face-up with legs bent toward the chest with your hand against the back of the thighs

With your other hand:

  • Insert the lubricated thermometer into the anal opening about ½ inch to 1 inch (about 1.25 to 2.5 centimeters), or until the tip of the thermometer is fully in the rectum. Stop if you feel any resistance.
  • Steady the thermometer between your second and third fingers as you cup your hand against your child's bottom. Soothe your child and speak quietly as you hold the thermometer in place.

  • Wait until you hear the right number of beeps or other signal that the temperature is ready to be read. Write down the number on the screen, noting the time of day that you took the reading.
  • A reading of 100.4°F (38°C) or above means your child has a fever.
  • Wash the thermometer with soap and water and label it for rectal use so it won’t be used to take oral temperatures.
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Reviewed by: Melanie L. Pitone, MD
Date reviewed: November 2022