Newborn Fever: When to Worry


Your baby’s first illness is never fun.

Here’s how to identify (and treat) a newborn fever.


Having a baby is a time of joy and excitement.

Sure, those sleepless nights are tiring, but the newborn smell, baby yawns, and cute smiles cause you to melt into a puddle on a regular basis. Then there are the trying (or downright scary) times, like your baby’s first illness. And fewer things cause more anxiety than a newborn fever.

We know it can be scary, but don’t fret. Read on to find out what can cause a newborn fever, when to worry, and what to do about it.


What Is a Newborn Fever?

In a newborn, a temperature of 100.4 or higher is considered a fever. If this sounds low, remember that newborns are tiny and their immune systems are not fully developed, so a fever in a newborn is a much lower temperature than a fever in a 5-year-old child.

For babies 0-1 month old, a fever is considered an emergency. For babies older than one month, consult with your pediatrician for further care instructions.

Symptoms of a newborn fever

What To Look For

Sometimes it can be difficult to recognize fever symptoms in newborns because they can mimic normal newborn behavior. It’s important to be mindful of any changes and take their temperature if you notice these symptoms.

  • Crying/Fussiness – For some, this will be the first sign of a fever or illness. Sure, babies cry a lot, but if you’re experiencing a prolonged episode of inconsolable crying, it could be a fever.
  • Excessive Fatigue – Newborns already sleep a lot, but if your baby starts favoring naps above eating, a fever could be to blame.
  • Reduced Appetite – Most babies will let you know when they’re ready for their next meal. If your baby suddenly has no interest, take their temperature to be safe.
  • Cold/Flu Symptoms – If your baby has developed a cough or congestion, check their temperature, too. (Then notify the pediatrician.)
  • Spitting Up – Again, spit up is normal in babies, but if it’s more frequent and in excess quantities, this could point to vomiting rather than spitting up.
  • Feeling Warm – This seems obvious, but it can be hard to gauge the temperature of your baby, especially on a warm day. Taking their temperature internally (rather than just feeling their forehead) is the best way to be sure.

A number of causes can lead to a fever in newborns.

Causes of Newborn Fever

Remember, a fever is a symptom, not an illness. A newborn fever is a clue that something else is going on.

The first cause of a fever is a common virus. Babies are especially vulnerable to viruses, so it is easy for them to pick up a cold or flu. While you likely have plenty of friends and family who want to meet your new baby, make sure that all visitors wash their hands and stay home if they’re sick.

Babies can also display a fever if they’ve gotten overheated.

A lot of parents think that their babies need to be bundled at all times but babies are actually quite good at regulating their body temperatures and don’t need much more than you do to feel comfortable. A general rule of thumb is to clothe them in one extra layer than you’re wearing. For example, if you’re in short pajamas, put them in long pajamas plus a swaddle.

Another cause for newborn fever, consider dehydration. In their first few days, babies can become dehydrated if mom’s milk hasn’t come in or you haven’t figured out the right adjustments for formula. This is why your pediatrician asks how many wet/dirty diapers they have in a day.


How To Take Your Newborn’s Temperature

Ear and forehead thermometers are easy to use, but rectal thermometers are the most accurate. Why? Unlike the ears and skin, the rectum is not influenced by outside factors such as a cool day or sun exposure. (If all you have is a forehead or ear thermometer, that’s fine, too.)

First, clean the thermometer with alcohol or soap and water. Gently lay your newborn on their tummy with their knees underneath them or on their back, holding their feet above their head.

If you want to use a little petroleum jelly or coconut oil to help glide the thermometer, that’s fine but not necessary. The tip of the thermometer should only go in ½-1 inch. Do not go further than this, as you could puncture the baby’s rectum walls.

Wait until the thermometer beeps and read the temperature. If it’s above 100.4, and the baby has been unbundled for 10 minutes, it’s time to call the doctor.

doctor taking baby's temperature with forehead thermometer

How To Treat a Newborn Fever

For newborns—that is, babies under one month old—it’s crucial to consult with your pediatrician first.

If your baby is under one month (or four weeks) they may instruct you to head to the emergency room to test for bacterial meningitis. (It’s not common, but it’s best to rule it out.)

If your baby is between 1-3months, then your doctor will probably tell you to try some acetaminophen (Tylenol) to bring the fever down. Always check with your pediatrician (or the dosing instructions) for the proper amount.

You can also give your baby some lukewarm baths—not hot, not cold. Dress them in light clothing and make sure they’re getting plenty of hydration. If your baby is breastfed, there is no harm in feeding them more than usual (if they’re interested).



Whether you’re a first-time parent or a seasoned pro, newborn fevers are never ideal.

You’re already stressed enough with the diapers, lack of sleep, and constant crying. Adding an illness to the mix is the last thing you need. Make sure to follow the advice above, don’t Google too much, and call your pediatrician.

Call us today if you have a question or need an appointment so that we can help your baby on their way back to health.

Kid Care Pediatrics

Kid Care Pediatrics has been in existence since October 2001. It was established by Omar A. Gomez, M.D. The practice philosophy at Kid Care Pediatrics is to provide quality pediatric medical care for children in a professional yet caring manner.

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