Newborn fever is an important health indicator—any temperature 100.4 or higher needs to be discussed with your baby’s doctor right away. A newborn’s immune system is immature and therefore even a low fever of 100.4 can indicate a serious infection. It’s important to know how to properly take your baby’s temperature.

The American Academy of Pediatrics urges parents to completely avoid mercury thermometers because of the risk of poisoning if the thermometer breaks. Instead, choose a digital thermometer. There are several types of digital thermometers:

  • Oral (not recommended for newborns)
  • Armpit and rectal digital
  • Tympanic, or ear thermometers
  • Temporal lobe thermometer, which is placed near baby’s temple

Until your baby is six months old, rectal temperature taking is the most accurate. To correctly take a rectal temperature, follow these steps:

  1. Try to calm your baby by soothing and rocking. It can be hard to get an accurate reading from a kicking and wiggling baby.
  2. Position your baby belly down, either on your lap or on a firm surface.
  3. Use a lubricant like Vaseline and gently slide the thermometer into baby’s anus about one inch. Distracting baby might help in staying still. A rectal thermometer should never be forced or cause any signs of pain.
  4. Wait until the thermometer beeps before removing it.

At six months of age, the ear method may be used, but this can be a difficult method to get an accurate reading. Ear thermometers tend to be more expensive and require accurate placement to get a good reading. Carefully follow the manufacturer’s guidelines. If in doubt, take a rectal temperature.


  • Babies that have a fever above 100.4°F should see a doctor immediately.
  • Do not use a mercury thermometer.
  • Rectal temperature taking is the most accurate until six months of age.
  • After six months, you can opt for using a thermometer in the ear, although it’s not always accurate.

Last reviewed by Sara Connolly, MD. Review Date: December 2018


  1. American Academy of Pediatrics. How to Take a Child’s Temperature.
  2. Jane M. Gould. Fever in the Infant and Toddler.


  1. I like that this is the most accurate way but still get nervous when I do it (my husband won’t do it at all). So I try to be fast while following directions. I think I get more worried than him because he does not seem to mind it at all. I haven’t had any incidents while doing it but during his 2-week-checkup he went #1 and #2 while the nurse was doing it. It was a little bit messy. lol


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