Fever in Babies & Children: When to Worry

Tips on temperatures for parents
mom taking sick child's temperature

Fevers can be a very scary thing for parents, especially for first-time moms and dads. You might wonder how high is too high or if you should call the doctor immediately if your child has one.

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“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. That starts with taking your child’s temperature using any variety of thermometers available, from standard oral thermometers to the newer temporal artery scanners.  

“You can use any of these devices, but a digital thermometer is generally all you need,” she says.  

It is most accurate to use a rectal thermometer for infants and young children. “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 is considered a fever for a toddler?

So what is a fever? Fever is defined as a temperature over 100.4 degrees Fahrenheit (38 degrees Celsius). Normal body temperature is 98.6 F (37 C). Everyone’s body temperature varies throughout the day, though, and can differ by age, activity level and other factors. For instance, a newborn’s body temperature can typically be normal at 99.5 F (37.5 C). 

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Don’t be alarmed if your child’s temperature varies, however. The magic number for fever is 100.4 F (38 C). 

When should you not worry about your child’s fever? Dr. Lim says doctors tend not to worry about: 

  • Fevers that last fewer than five days. If your child’s behavior is relatively normal, you don’t need to be concerned if they continue to be playful and they’re eating and drinking normally. (Although, they may seem more tired than usual). 
  • Temperatures of up to 102.5 F (39 C) in a child 3 months to 3 years of age, or up to 103 F (39.4 C) if your child is older. These temperatures can be common, but not necessarily worrisome. 
  • Low-grade fevers. If your infant or child was recently immunized, these can be normal if they last fewer than 48 hours. A low-grade fever is determined if your child’s temperature is between 99.6 and 100.3 F (37.5 to 40 C).

When to take your toddler to the ER or doctor for a fever

Now for the important question: When should you be worried about a fever? Call your doctor if and when: 

  • An infant younger than 3 months of age develops a fever. 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 your pediatrician if your baby’s temperature drops below 97.7 F (36.5 C) rectally. 
  • Your child’s fever lasts more than five days. Your pediatrician may need to investigate further for underlying causes. 
  • Your child’s fever is higher than 104 F (> 40 C)
  • Your child’s fever does not come down with fever reducers.  
  • Your child is not acting themselvesis difficult to arouse or is not taking in enough liquids. Babies who aren’t wetting at least four diapers per day and older children who are not urinating every eight to 12 hours may become dangerously dehydrated, Dr. Lim says. 
  • Your child was recently immunized and has a temperature above 102 F ( 38 C) or a fever for more than 48 hours. 
  • You are concerned. If you are uncomfortable with your child’s temperature or illness, call your doctor or nurse practitioner to discuss it. 

Can fever cause a seizure?

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

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  1. Put your child on their side. 
  2. Do NOT put anything in your child’s mouth. 
  3. 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. 

What to do about multiple fevers

“If your child has persistent or multiple episodes of fever and a pediatrician cannot figure out what is causing them, they may refer your child to a specialist,” Dr. Lim says. A pediatric infectious disease expert or pediatric rheumatologist may be able to get to the bottom of the issue. 

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