Baby Temperature: Tips & When to Seek Help

As a mama, we know keeping an eye on baby temperature is important to you. Whether that’s making sure your little one is wrapped up and cozy in the winter (in the cutest bear onesie, obvs) or helping them stay cool and comfortable in the summer.
And you may have a few questions about how to check that your little one is (much like Baby Bear’s porridge) not too hot and not too cold: What is the normal body temperature of a baby? What is a high temperature for a baby? Is a temperature of 99 a fever for a baby?

In this article, we’ll be answering all these questions about infant body temperatures – so grab that thermometer and get ready to become a temperature-checking pro.

Table of Contents 📝

What is a normal temperature for a baby?

As for us grownups, normal baby temperature varies from baby to baby. It’s also slightly different depending on the type of thermometer reading you take. A rectal thermometer reading (up baby’s bum) is the most accurate way of taking a baby’s temperature, particularly under 3 months old.

A normal baby temperature range based on a rectal thermometer reading is about 98 to 100.3 degrees Fahrenheit. However, a normal baby temperature armpit reading is usually about 1 to 2 degrees F lower than a rectal reading.

Checking baby temperature: How to take a thermometer reading

If you’re ever concerned that your baby looks a little hot, or their skin feels hot and sweaty to touch, you can easily check their temperature using a digital thermometer or temporal artery thermometer. Old-fashioned mercury thermometers aren’t recommended, as there’s a risk they can shatter and cause mercury poisoning.

So, what’s the best way to check baby temperature for different age groups?

Newborn to 3 months

For newborn temperature checks, rectal readings using a digital thermometer are the most accurate. Remember to read the thermometer’s instructions before you use it.

Here’s how you would go about taking a reading:

• Clean the thermometer as advised in the instructions.
• Lay your baby down on their belly, or on their back with their legs bent toward their chest.
• Apply a bit of petroleum jelly to the thermometer tip.
• Gently insert the thermometer, up to a depth of ½ to 1 inch. (Never force it if there’s resistance.)
• Hold the thermometer in place until it beeps.
• Gently remove the thermometer and read the temperature.

If you have another thermometer for oral readings (for you or older kids temperature checks), remember to keep that separate from the rectal thermometer and label both clearly!

3 months to 4 years

For older babies and toddlers, you can still take a rectal digital thermometer reading or you can measure their temperature under the armpit. Keep in mind that underarm readings are less accurate though. If in doubt, double check the temperature using another method.

You could also try a temporal artery thermometer, which uses an infrared scanner to measure the temperature of the temporal artery in your little one’s forehead (you can even use this when they’re asleep – win!). Another option, from 6 months old, is to use a special digital ear thermometer.

What temperature is too high for a baby?

A higher than normal temperature may mean that your baby has a fever. Now, this could be something that will pass quickly, perhaps when you’ve taken steps to cool your baby down (more on that below!), or it may be a sign of illness that needs further attention.

A fever is defined as a temperature of:

• 100.4 degrees Fahrenheit or over (rectal, ear or temporal artery reading)
  or
• 99 degrees Fahrenheit or over (armpit reading).

Important note: Seek medical advice immediately if your baby is less than 3 months old and has a fever, even if they have no other symptoms of illness.

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When should you worry about a baby’s fever?

If your baby is over 3 months old and has a fever, but they otherwise seem happy and comfortable (drinking, sleeping, and playing as usual) then it’s fine to wait and see if the fever passes on its own. They may have simply become a little overheated or perhaps they have a minor infection, and the fever is a good sign that their body is fighting it off.

However, a fever accompanied by other symptoms, such as ear pain, an unexplained rash, or vomiting and diarrhea, could mean that your baby has an infection or illness that needs medical treatment.

So when should you consider calling your pediatrician about baby fever?

• Newborn to 3 months: As noted above, always seek urgent medical advice if you have a baby in this age group and they have a fever (temperature of 100.4 degrees F or higher).
• 3 to 6 months: If your baby has a temperature of 100.4 to 102 degrees F and is clearly uncomfortable, or if their temperature is over 102 degrees F with no other symptoms.
• 6 to 24 months: If your baby has a temperature of over 102 degrees F for longer than one full day, even if they have no other symptoms. If there are other symptoms, you might want to call your doc sooner.

Ultimately, you’ll use your mama senses to make that judgment call: if your baby has a high temperature and you’re worried about their wellbeing, don’t hesitate to contact your healthcare provider.