A fever isn’t fun for anyone…and when it comes to a baby, a fever can really make a parent sweat. While a fever can be serious, it’s also a normal part of growing up. Fortunately, a few simple fever facts can help you figure out whether you should be concerned about your baby’s temperature…or if you can chill out.

Signs of a Fever in Babies

As parents gain experience, they can often just feel the baby to tell if they’re warm. Of course, babies also feel hot and sweaty when they’ve been in a warm room or are overdressed. But most babies who feel warm—but do not have a fever— have a normal digital temperature.

How to Check for a Fever in Babies by Age

A digital thermometer is a “must have” in your baby’s first aid kit. Digital thermometers usually have a plastic, flexible probe with a temperature sensor at the tip and an easy-to-read digital display on the other end. (Check out our guide to the best thermometer for taking your baby's temp.)

  • For babies younger than 3 months: You'll get the most reliable reading by using a digital thermometer to take a rectal temperature. Call the doctor if your infant is younger than 3 months old and has a temperature of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher.
  • For babies between 3 months and 6 months old: A digital rectal thermometer is still the best choice. A temporal artery thermometer (aka a forehead thermometer) also can be used.
  • For kids between 6 months and 4 years old: You can use a digital thermometer to take a rectal temperature. You also can use a tympanic (ear) thermometer or a digital thermometer to take an axillary (armpit) temperature, but they're less accurate.

What is considered a high fever in babies?

A normal temperature for a baby is about 97 to 100.3 degrees Fahrenheit (usually it’s around 98.6 degrees, but there’s some variation from person to person). You’ll know your baby has a fever when their rectal temperature spikes to 100.4 or higher (38 degrees Celsius).

Any baby under 3 months with a rectal temperature of 100.4 or higher, always, always, always needs to be checked by a doctor. And any child with a fever over 104 degrees needs to be evaluated—so if you see that number, don’t wait to give your doctor a call!

What causes fever in babies?

Most often, a baby’s fever is caused by infection. When your baby or toddler has an infection, their body temperature rises as their immune system suits up to battle the illness (hey, fighting off bacteria and viruses can really work up a sweat!).

Vaccines can also cause a brief fever in babies, which is a normal reaction that signals that your baby’s immune system is working to make important antibodies to prevent disease.

Other Causes of Rising Temperature in Babies

Your child's body temperature can rise over 104 degrees Fahrenheit (40 degrees Celsius) by overheating, such as being in a hot car. This is an emergency situation where your baby needs to be cooled as soon as possible and seen by a doctor. 

Can constipation cause fever in babies?

Though it’s possible your baby might have a fever and be constipated at the same time, constipation itself does not cause fever. If your baby is constipated and has a fever, be sure to call your doctor—it’s possible there’s an underlying health issue that’s behind both. 

Does teething cause fever in babies?

The idea that teething causes a fever in babies is largely a myth. ​​Research has shown that teething does not make babies sick. If your teething baby has a fever call your doctor to rule out an infection. 

What is the best thing to address fevers in babies?

A fever can cause young children to become fussy, lethargic, and sweat so much that they become dehydrated (dark yellow pee and a dry, sticky tongue). That’s why it’s good to offer plenty of fluids to help bring down a fever for babies.
One of the signs that make pediatricians the happiest is when a baby wants to play a little…even if they have a fever. Their body temperature dropping even one degree can help them feel better. 

Home remedies for a fever in babies:

You don't have to do anything to treat a baby fever if your child is drinking and wetting diapers adequately. If they seem content and aren't in any discomfort, medication isn’t necessary. However, there are a few things you can do to make them more comfortable: 

Keep your baby cool to reduce the fever. Dress your baby in loose, breathable cotton clothing. Don't cover them in blankets or layers of clothes—overdressing them can cause the fever to climb or prevent it from coming down. If your baby’s hands and feet are cold, ibuprofen or acetaminophen may help. (Talk to your child's doctor first.) Use lightweight pajamas and swaddles and make sure the room isn't too hot. Turn on a fan if the room feels warm or stuffy. 

Try a bath. Make sure it’s a bit warm…if it’s too cool it will be too shocking for your baby. (The cooling of the body that happens with a bath occurs mostly because of evaporation of water off your baby’s body.) It also helps to give a bath after you’ve given fever-reducing meds.

Talk to the doctor about medication to reduce a baby fever. If your baby is under 3 months, don't give them medications without talking to your doctor. For older babies, it's still a good idea to check in. In general, Tylenol (acetaminophen) can be taken every 4 to 6 hours. Ibuprofen can be given every 6 to 8, as long as your baby is at least 6 months old. (Weigh your baby and check the package for the correct dosage...and read our guide to baby pain- and fever-relievers.) Your doctor might give you instructions for taking both together or even giving a little more, depending on your baby’s condition. Never give medications containing aspirin. 

Fever in Babies: When to Worry

A baby fever on its own isn't necessarily concerning, but combined with certain other symptoms, you will want to call your doctor for advice or head to an emergency room. These can include:

  • More drowsy, listless, not alert or interested in playing…even when fever comes down
  • More fussy, irritable, not interested in playing…even when the fever comes down
  • Severe sore throat or ear pain
  • Has certain immune system conditions such as cancer, or is taking steroid medications
  • Dry mouth, no tears, and fewer wet diapers than normal
  • Is under 3 months of age and has a temperature above 100.4 degrees
  • Has fever over 104 degrees at any age
  • Had a seizure
  • Appears to have a headache, stiff neck, rash, continued vomiting or diarrhea
  • Fever that lasts more than 24 hours when your child is under 2 years old
  • Fever that lasts for more than 72 hours, or three days, when your child is 2 and older

A fever can be frazzling, so don't hesitate to call your doctor with your questions. It's always better to be on the safe side when it comes to your baby's health. 

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About Dr. Harvey Karp

Dr. Harvey Karp, one of America’s most trusted pediatricians, is the founder of Happiest Baby and the inventor of the groundbreaking SNOO Smart Sleeper. After years of treating patients in Los Angeles, Dr. Karp vaulted to global prominence with the release of the bestselling Happiest Baby on the Block and Happiest Toddler on the Block. His celebrated books and videos have since become standard pediatric practice, translated into more than 20 languages and have helped millions of parents. Dr. Karp’s landmark methods, including the 5 S’s for soothing babies, guide parents to understand and nurture their children and relieve stressful issues, like new-parent exhaustion, infant crying, and toddler tantrums.

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Disclaimer: The information on our site is NOT medical advice for any specific person or condition. It is only meant as general information. If you have any medical questions and concerns about your child or yourself, please contact your health provider.