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How do I take baby’s temperature?
Q: How do I take my baby’s temperature? She is 9 months old. Should I use a rectal thermumeter? And, if so, how long should I wait before reading it?
Sara Casper
A: Sara, there are many different options for taking your baby’s temperature. The option you choose depends on your doctor’s recommendation and your comfort level.

The standard ways to take an infant’s temperature are with the ear thermumeter, or with a plastic digital thermumeter under the arm or rectally. (Don’t use a glass mercury thermumeter since it can break and leak toxic mercury vapor.) These thermumeters tell you when it’s time to read the temperature. The ear thermumeter displays the temperature immediately while the digital thermumeter beeps when it reaches your child’s temperature reading.

Although the rectal temperature is considered most accurate, it can be uncomfortable for the child and parent, and it exposes you more to your child’s germs. In most cases, the ear thermumeter and underarm (axillary) digital thermumeter are accurate enough.

Here are the basic techniques for taking your baby’s temperature:

Ear thermumeter:
  • Cover the thermumeter with a fresh plastic tip.

  • With one hand, hold your child’s ear steady.

  • With the other hand, gently insert the thermumeter into your child’s ear canal until you get a tight seal.

  • Press the start button and read the temperature displayed.

  • Discard the used plastic tip.


  • Underarm digital thermumeter:
  • Place the tip of the thermumeter under your child’s armpit, between the bare skin of the arm and chest.

  • Hold her arm tightly against her chest.

  • When you hear the beep, remove and read the thermumeter.


  • Rectal digital thermumeter:
  • Clean the tip of the thermumeter with soap and cool water.

  • Put a small amount of lubricant (such as petroleum jelly) on the tip, and turn on the thermumeter.

  • Lay your child belly-down across your lap with his bottom exposed.

  • Gently insert the thermumeter ½ to 1 inch into his anus. Hold the thermumeter in place by cupping your hand over your baby’s bottom.

  • When you hear the beep, remove and read the thermumeter.

  • Turn off the thermumeter. Wash the thermumeter and your hands with soap and warm water.


  • Newer types of thermumeters include a dummy thermumeter, which a baby sucks on, and a temporal artery thermumeter, which is rolled across a child’s forehead. These thermumeters are currently being evaluated for accuracy. You can ask your doctor for advice about them.