How to Check a Newborn’s Temperature

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If your baby seems unusually fussy and warm, knowing how to accurately take your newborn’s temperature is an important skill. Let’s go through the steps and tips to ensure that you know how to check a newborn’s temperature and that you’re doing it correctly and safely.

What Is Considered a Fever for a Baby?

First off, it’s important to know why monitoring your newborn’s temperature matters. A newborn’s immune system is still developing, making them more susceptible to infections. An abnormal temperature can be one of the first signs of illness. Even a slight fever can be a sign of a serious infection in a newborn.

What’s Normal and When to Worry

  • Normal Range: A normal rectal temperature for a newborn ranges from 97.9°F to 100.4°F (36.5°C to 38.0°C).
  • When to Call the Doctor: If your newborn has a rectal temperature above 100.4°F (38.0°C) rectally, it’s important to contact your pediatrician, especially if they’re under 3 months old.

Key take-away: A rectal temperature of 100.4°F is considered a fever for a newborn.

How to Check a Newborn’s Temperature: Choosing the Right Thermometer

Digital thermometers are recommended for newborns. They are quick, accurate, and can be used rectally, orally, or under the arm. Avoid mercury thermometers, ear, or forehead thermometers for newborns, as they can be less accurate for babies under 30 days old.

Depending on where the temperature is taken on the body, you will get different readings on the thermometer.

  1. Rectal Temperature:
    • Considered the most accurate for infants and young children.
    • Typically read higher than oral and axillary temperatures.
    • Normal range: 97.9°F to 100.4°F (36.5°C to 38.0°C).
  2. Oral Temperatures:
    • Not typically recommended for newborns or very young children due to the difficulty of getting an accurate reading.
    • Generally, read slightly lower than rectal temperatures by about 0.5°F to 1°F (0.3°C to 0.6°C).
    • Normal range: 97.6°F to 99.6°F (36.4°C to 37.6°C).
  3. Axillary (Underarm) Thermometer
    • Less invasive and easier to perform, but less accurate than rectal readings.
    • Usually read lower than oral temperatures by about 0.5°F to 1°F (0.3°C to 0.6°C).
    • Normal range: 96.9°F to 98.9°F (36.0°C to 37.2°C).
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Key take-away: The most accurate way to find a baby’s temperature is to use a digital thermometer rectally.

How to Check a Newborn’s Temperature: Steps for Taking a Rectal Temperature

Rectal temperatures are considered the most accurate for newborns. Here’s how to check a newborn’s temperature rectally:

  1. Use the Right Tool: Use a digital thermometer designed for rectal use. These typically have a flexible tip and a safety stop to prevent over-insertion.
  2. Clean the Thermometer: Use rubbing alcohol or soapy water to clean the tip of the thermometer, then rinse it with cool water.
  3. Lubricate the Tip: Apply a small amount of petroleum jelly to the tip of the thermometer so that it slides in comfortably.
  4. Position Your Baby: Lay your baby on their back and gently lift their legs, or place them belly-down on your lap.
  5. Insert the Thermometer: Gently insert the lubricated thermometer about half an inch into the rectum. Hold it in place and never force it in. You risk causing a rectal tear if the thermometer is inserted too forcefully or deeply.
  6. Wait for the Beep: Most digital thermometers will beep when they’re done. This usually takes a few seconds.
  7. Remove and Read: Carefully remove the thermometer and read the temperature.
  8. Clean Again: Clean the thermometer after each use.

Key take-away: Never insert a rectal thermometer too forcefully or deeply.

How to Check a Newborn’s Temperature: Taking an Axillary (Underarm) Temperature

If you’re uncomfortable with a rectal reading, an underarm (axillary) temperature is an alternative. With my own children, if I sense that my baby may have a fever, I’ll often screen for a fever by taking an axillary temperature, just for the sake of ease. If that gives a high reading, I’ll follow up by taking the temperature rectally to get a more accurate number.

Here’s how to check a newborn’s temperature axillary:

  1. Position the Thermometer: Place the thermometer tip in the center of your baby’s armpit.
  2. Hold Your Baby’s Arm: Gently hold your baby’s arm against their body to keep the thermometer in place.
  3. Wait and Read: Like with a rectal reading, wait for the beep, then remove the thermometer and check the temperature.
    • Just keep in mind that an axillary thermometer reads lower than a rectal temperature. This means that depending on the accuracy of the thermometer, an axillary temp as low as 98.4°F may indicate a fever. If you suspect a fever in your newborn, you’ll need to contact your doctor or follow up with a rectal temp first.

Key take-away: Axillary temps are easier to take but reader lower than a rectal temperature.

Tips for a Smooth Process

  • Stay Calm: Your baby can pick up on your emotions. Stay calm and reassuring throughout.
  • Consistency: Use the same thermometer and method each time for consistency.
  • Never Leave Baby Unattended: Always keep one hand on your baby during temperature checks.


Knowing how to check your newborn’s temperature is a simple yet vital part of caring for their health. By following these steps, you can ensure that you’re getting an accurate reading, which is crucial in keeping your precious little one healthy and safe.


Herzog LW, Coyne LJ. What is fever? Normal temperature in infants less than 3 months old. Clin Pediatr (Phila). 1993 Mar;32(3):142-6. doi: 10.1177/000992289303200303. PMID: 8453829.

Hockenberry, M., Wilson, D. (2011). Wong’s Nursing Care of Infants and Children, 9th Edition. pgs 145-147, 242-243.

Mogensen CB, Wittenhoff L, Fruerhøj G, Hansen S. Forehead or ear temperature measurement cannot replace rectal measurements, except for screening purposes. BMC Pediatr. 2018 Jan 26;18(1):15. doi: 10.1186/s12887-018-0994-1. PMID: 29373961; PMCID: PMC5787302.

Morley CJ, Hewson PH, Thornton AJ, Cole TJ. Axillary and rectal temperature measurements in infants. Arch Dis Child. 1992 Jan;67(1):122-5. doi: 10.1136/adc.67.1.122. PMID: 1739325; PMCID: PMC1793545 (2023). Fever Temperatures: Accuracy and Comparison. Retrieved at,lower%20than%20an%20oral%20temperature.

Meet Katie Griffin

I’m a registered nurse, Lamaze certified childbirth educator, and the mother of 7. I help women realize their dream of a natural, intimate, and empowering hospital birth.

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If your baby seems unusually fussy and warm, knowing how to accurately take your newborn’s temperature is an important skill. Let’s go through the steps and tips to ensure that