When Is a Fever Too High?

Family with sick children
How long will the flu last?. Tim Hawley/DigitalVision/Getty Images

Many people -- especially parents -- worry about fevers and want to know "how high is too high?" You would think there would be an easy answer to this question. A cutoff number that means "Danger!  Head straight to the ER".

Unfortunately, it just isn't that simple.

Most of the Time, Fevers Won't Hurt You

That's right. Most of the time, fevers aren't dangerous, they aren't going to fry your brain and there is often very little that will be done at the ER that can't be done at home to bring a fever down.

I understand that is hard to believe and goes against your every fear about fevers, but the medical evidence just isn't there to support any claim that they are dangerous for a majority of people.

Fevers Can Be Beneficial

Most of the time, fevers are actually a good thing. They are a natural way that our bodies fight off infections.

A part of the brain called the hypothalamus acts as a thermostat for the body. Most of the time it keeps our body temperatures around 98.6 degrees F (37 degrees C). But when we get sick, the thermostat resets and increases the temperature of the body to make it more difficult for germs to live and multiply.

What to Watch For

If you or your child has a fever but are still fine for the most part, treatment is not necessary. If your child is playing and still has energy, there is no need to treat the fever.

However, many times an increased temperature will make us feel pretty bad.

Our bodies ache, we have no appetite and it's hard to do much of anything. If this is how you are feeling, taking a fever reducer like Tylenol (acetaminophen) or Motrin/Advil (ibuprofen) should help you feel better.

However, the effects of these medications are only temporary -- they work for 4 to 8 hours and then wear off.

Meaning your fever may come back and you may need to take more medication. This doesn't mean something is wrong or that it didn't work.

For most adults and older children, the number on the thermometer is not important when determining if a fever is something to worry about. However, that is not the case with younger children.

If your child falls into one of these age groups, this is what you need to watch for.

Infants Up to 3 Months Old

  • Rectal temperature higher than 100.4 degrees F (38 C)

If your baby is younger than 3 months old and has a fever higher than 100.4 degrees, contact her healthcare provider or go to the emergency room. A fever in an infant this young can indicate a potentially serious illness.

Babies and Children Between 3 Months and 3 Years Old

  • Temperature higher than 102.2 degrees F (39 C)

If your child is between the ages of 3 months and 3 years old and has a fever higher than 102.2 degrees F, contact his healthcare provider -- even if it's after hours. His healthcare provider can help you determine whether or not the fever is caused by something that needs to be treated or not and can tell you if your child needs to be seen.

Everyone Else -- When Is It Really Too High?

  • Temperature higher than 107.6 degrees F (42 C)

If you are looking for an absolute cut-off number when it comes to fevers -- 107.6 F is it. However, the body temperature almost will never get this high on its own without some sort of extenuating circumstances, such as being in an extremely hot environment (which is technically hyperthermia, not fever) or an existing neurological condition that affects the function of the hypothalamus.

Don't Rely on Numbers Only

In most cases, what you need to watch for is behavior and other symptoms, not the number on the thermometer.

If you are caring for a child with a fever and she is playing, smiling and eating or drinking, it is unlikely that there is any cause for concern.

However, if you are caring for a child with a fever and he won't smile or play at all, even after taking fever reducers (remember -- they can take an hour to work), you should contact his healthcare provider or seek medical attention.

Tools to Help Adults Evaluate Their Own Situation

Adults are typically better able to determine when our symptoms are making us feel so bad that we need to seek medical treatment, but if you aren't sure, we have tools that can help you evaluate what is going on and when you should take action.


"Fever and Taking Your Child's Temperature". Your Kid's Body. KidsHealth. The Nemours Foundation. 18 Aug 14.

"Fever". MedlinePlus 15 Aug 14. US National Library of Medicine. US Department of Health and Human Services. National Institutes of Health. 18 Aug 14.

Continue Reading