Fever in Babies and Children: When To Worry

Behavior and age are important clues
mom taking sick child's temperature

Your knee-jerk reaction when your child develops a fever may be to immediately start ringing the alarms. Fevers can be scary for parents, especially first-timers. You might wonder how high is too high or if you should call the doctor immediately if your child has one. Certainly, something must be done, right?  

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Well, not always. It turns out that not all fevers are something to fret about. And knowing the difference between a fever that needs treatment and a fever that can be left to run its course can help your child get better faster — and with less stress on you. 

“Every child will eventually experience a fever, no matter how careful you are,” says pediatrician Tracy Lim, MD. And it’s important for parents to know what to do when this happens.  

We talked with Dr. Lim about how to spot a worrisome fever in children and what to do when your child has a fever.  

Tips on taking your child’s temperature 

First thing first. To know if your child is running a fever, you’ll need to take their temperature. But a look at online stores or a trip down the pharmacy aisle can leave you wondering which of those thermometer gadgets you actually need.  

There’s a wide variety of thermometers available, from standard oral thermometers to temporal artery scanners.

“It is most accurate to use a rectal thermometer for infants and young children, but if you feel uneasy doing this, use whichever device makes you most comfortable,” Dr. Lim says. “In older children, an oral temperature is most accurate, if the child is able to tolerate it.” 

What’s considered a fever? 

A “normal” body temperature is 98.6 degrees Fahrenheit, or 37 degrees Celsius, but that doesn’t mean you have to hit the panic button if your child’s temperature inches above that. Everyone’s temperature will vary a little throughout the day. It can also differ by age, activity level and other factors. 

The type of thermometer you use will change the definition of what’s actually a fever for your child. Different kinds of thermometers have different levels of accuracy. This fever chart can help you understand the results you’re seeing.

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Child fever temperature chart 

Child’s ageBest type of thermometerWhat’s considered a fever?When to call a healthcare provider
0 to 2 yearsRectal
100.4 F (38 C)
99 F (37.22 C)
Any fever in babies under 3 months of age, or a fever over 104 F (40 C) in older kids. 
2 to 5 yearsRectal
100.4 F (38 C)
100.4 F (38 C)
99 F (37.22 C)
Fever over 104 F (40 C), or a fever that won’t come down with fever-reducing medication. 
5+ yearsEar
100.4 F (38 C)
100 F (37.77 C)
99 F (37.22 C)
Fever over 104 F (40 C), or a fever that won’t come down with fever-reducing medication. 

Some fevers are OK 

It can be worrying to see your kid spike even a mild fever. We get it. But the truth is that a fever is actually a sign that your child is fighting off germs. It’s doing what it’s supposed to. And that’s a good thing.  

When should you not worry about your child’s fever?  

Dr. Lim says doctors tend not to worry about a fever if it’s mild, lasts fewer than five days and doesn’t affect your kid’s day-to-day activities.  

The following fevers can be monitored at home. If needed, you can also treat them with:  

  • Fever-reducing medication such as infant or children’s acetaminophen (Tylenol®). 
  • Cool compresses. 
  • Plenty of liquids to prevent dehydration
  • Rest. 

A temperature below a certain threshold  

In a child over 4 months, fevers of up to 104 F shouldn’t cause alarm. A mild fever that lasts up to five days is OK for most kids.

A fever that doesn’t affect your child too much 

If your child’s behavior is relatively normal, you don’t need to be concerned. Monitor them and see if they continue to be playful and if they’re eating and drinking normally. A child with a fever may seem more tired than usual, but if they’re otherwise acting normal, there’s no reason to worry.

When to call a doctor for a fever 

Now for the important question: When should you be worried about a fever? Call your doctor in these cases. 

Fevers in infants under 3 months 

Fevers may be your infant’s only response to a serious illness. Especially in newborns, a low temperature can also be a sign of serious illness. Call a healthcare provider if your baby has any fever or if their temperature drops below 97.7 F (36.5 C) rectally.  

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High fever in infants and children over 3 months

In babies and children over 3 months, call a healthcare provider if your child’s fever is higher than 104 F (40 C), or if the fever doesn’t come down with a fever-reducing medication. 

Your child’s fever lasts more than five days 

Your pediatrician may need to investigate further for underlying causes.  

Your child’s fever doesn’t come down with fever reducers 

Infant and children’s versions of medications like acetaminophen can be used at home in babies and children if OK’d by their healthcare provider. The medications should work quickly to reduce your child’s fever. Contact a doctor if your child’s fever continues even after using a fever-reducing medication. 

Your child isn’t acting like themselves 

If your child shows these signs of illness, it’s time to call a healthcare provider:  

  • Difficult to arouse.  
  • Not taking in enough liquids.  
  • Babies who aren’t wetting at least four diapers per day.  
  • Older children who aren’t urinating every eight to 12 hours.   

You’re concerned 

Sometimes, parents’ instincts are meaningful. If you’re uncomfortable with your child’s temperature or illness, call a healthcare provider to discuss it.

Can fever cause a seizure? 

Seizures can be a very scary side effect of fevers in some children. Febrile seizures occur in 2% to 4% of all children under age 5. Not all seizures cause jerking movements in the body. Dr. Lim says some seizures look like “passing out.” If your child develops a seizure:

  • Put your child on their side.
  • Do NOT put anything in your child’s mouth.
  • Call 911 if the seizure lasts more than five minutes.  

If the seizure lasts fewer than five minutes, call your physician or seek immediate medical attention.  

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