Newborn Temperature Guide

Keeping an eye on your newborn’s temperature can become a bit of an obsession in the early days and weeks — and with good reason. Too hot or too cold can mean a cranky baby, and anything far above or below the normal baby temperature range can be cause for concern.
That’s why it’s helpful to know what a normal newborn temperature is, how to measure it, and how to spot if your newborn has a fever. And in this guide, we explain all.

In this article: 📝

What is a normal temp for a newborn?

A normal newborn temperature is between 98 and 100.3 degrees Fahrenheit when taken with a rectal thermometer (the easiest and most accurate way of taking a baby’s temperature, especially one under 3-months-old). With an underarm thermometer, the normal temperature range is typically 1 to 2 degrees lower than the rectal reading.

Anything above this range is a fever, and anything below might be hypothermia.

How to tell if baby is too hot (or too cold)

Touching your baby is often the first way you can tell their temperature is off. And babies can feel uncomfortably cold or hot even if the thermometer says their temperature is normal.

The quickest way to tell if your baby is too cold or too hot is to simply feel the back of their neck or their chest. If it’s sweaty or if it’s especially cold to the touch, that’s usually a clue to add or remove some clothing layers.

How do I take my newborn’s temperature?

There are several options for taking a newborn’s temperature. You can do it via the bottom (rectally), mouth (orally), under the arm (axillary), in the ear, or on the forehead.

As mentioned above, rectal thermometers are the easiest and most accurate for newborns. You’re less likely to get an accurate reading with an in-ear thermometer, while a forehead reading can be thrown off by sweat or direct sunlight.

To take a rectal reading:

• Make sure the thermometer is clean.
• Lay your baby on their tummy or their back with their legs bent gently towards their chest.
• Apply a small blob of petroleum jelly around the bulb of the thermometer.
• Carefully insert it into your baby’s rectum, no more than half an inch (or 1 inch, if older than 6 months).
• Hold it in place until it beeps or for at least one minute.
• Remove the thermometer and check the temperature display.

How do you know if a newborn has a fever?

A temperature of 100.4 degrees F or higher with a rectal thermometer or 99 degrees F with an armpit thermometer is considered a fever.

Beyond taking their temperature, you can usually tell your newborn has a fever if they’re sleeping and/or eating poorly, they’re lethargic, or if they show no interest in play.

It’s important to note that a fever isn’t an illness, but rather a symptom. If your baby’s running a fever, it usually means their immune system is heating up baby’s body to fight off an underlying infection. Other causes of fever in newborns can include adverse reactions to vaccinations, overheating due to wearing too many layers, or spending too much time outdoors on a hot day.

When to call your doctor about newborn fever

If your baby is under 3-months old and has a fever (even without other symptoms), it’s considered an emergency. If your newborn has a fever with no other symptoms, you can call your child’s pediatrician or after-hours answering service and see what they say.

But if your newborn has a fever and any of the symptoms below, it’s best to take them straight to an emergency room:

• Listless or not responsive
• Trouble breathing or eating
• Blotchy skin or a rash (often a symptom of meningitis)
• Cranky, irritable, or crying more than usual
• Showing signs of dehydration, including no tears when crying, dry mouth or lips, and fewer wet diapers

When it comes to infant fever, remember to trust your mama instincts. You know your baby better than anyone. If you think something’s amiss, it’s always better to call early and be wrong. Pediatricians get calls about possible fevers all day long, so they’re used to it and will be able to help you quickly.