Fevers in adults, children, and toddlers: when to worry

Published: December 18, 2022


Warm forehead. Flushed cheeks. Glassy eyes. These are the classic signs of fever. They may look alike in adults and children, but beneath the surface they warrant different degrees of concern. Whether you're a middle-aged or senior adult, or the parent of a young child, it's important to know how to assess a fever—especially during this triple-header season of flu, Covid, and RSV (Respiratory Syncytial Virus)—and respond to it.


What is considered a fever and what causes fevers?

1. What is a fever and why do we get them?

A fever is an elevated body temperature of 100.4 degrees F or higher. It is a natural part of the body’s immune response.

Our bodies are built to handle fever. It will not harm you. It will not cause brain damage. Fever means that your or your child's body is working as it should. In most cases, it will resolve on its own.

2. What causes fever in adults?

In adults, viral infections commonly cause fevers. Such infections include COVID-19, the flu, and the common cold. These types of infections typically go away on their own after a few days. Less commonly, bacteria cause fevers in infections like pneumonia or urinary tract infections.

3. What causes fever in children?

In children, fevers also usually stem from viral infections, like Covid, flu, or RSV. They tend to be short-term and acute, lasting for two to three days. Bacteria are the second big bucket of germs that can cause fevers in kids in conditions like ear infections and pneumonia.

4. Is 98.6 still considered the "normal" body temperature?

Yes and no. You've probably always heard that the average body temperature is 98.6, but the truth is there's a much wider range—from about 97 to 99 degrees F.

So why is 98.6 suddenly a myth after all these centuries? Research suggests body temperatures are falling overall. Doctors have a few ideas about why this is, including lower metabolic rates, lower rates of infection, and more advanced thermometers.

To find your 'normal' temperature, you must take it the right way. The most accurate method is by mouth, at least 30 minutes after eating or drinking anything hot or cold.

5. What is considered a high fever in adults?

A high-grade fever in adults is 103 degrees F. or higher.

6. What is considered a high fever in children?

For infants ages zero to three months, a temperature above 100.4 degrees F. is considered a 'fever of concern' and warrants medical attention.

For children ages three months to three years, a temperature above 102 degrees F. is a 'fever of concern,' as is a temperature above 103 degrees F. in older children.

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How should you treat a fever and when should you seek medical help?

1. What is the best way to treat a fever?

In most children and adults, fever doesn't require treatment other than rest and plenty of fluids.

If fever is making your child uncomfortable or preventing them from eating or drinking, then you can give them children's Tylenol (acetaminophen) or Advil (ibuprofen). If their fever is high and prolonged, then you can alternate Tylenol and Advil. Tylenol can work up to six hours, depending on the child and illness, while Advil can work up to eight hours.

Do NOT give your child aspirin, which is associated with an increased risk for Reye's syndrome, a rare but serious condition that causes confusion, swelling in the brain, and liver damage.

Be sure to follow all dosing directions for all medication. Do not exceed the number of recommended doses, and make sure that the amounts you give correspond with the age and weight ranges listed on the label.

If you want your children to have fewer fevers, and to worry less when they do, make sure they're up to date on all their vaccinations.

2. When should an adult seek emergency or immediate care for a fever?

You should seek emergency or immediate medical attention for a fever if you:

  • Have a high temperature that has not gone down after taking Tylenol or Advil
  • Have a temperature that lasts several days or keeps coming back
  • Live in an area where people have high rates of COVID-19
  • Have serious health conditions like diabetes, heart disease, cancer, lupus, or sickle cell anemia (non-infections like these can cause fever as well)
  • Are not fully vaccinated against COVID-19 and have developed a high-grade fever
  • Are pregnant
  • Recently returned from travel overseas
  • Get infections often
  • Are receiving chemotherapy, in which case you should seek medical attention immediately if the fever lasts for more than one hour
  • Have recently been bitten by a tick

3. When does a child require emergency or immediate care for a fever?

You should see your pediatrician or head to a pediatric emergency department in these situations.

  • A child younger than three months who develops a fever requires medical attention. Newborns are so small, and their immune systems are not developed enough to fight off infection. Because we can't always tell—and they can't tell us—why they have a fever, we treat every fever seriously.
  • All children whose fevers last four to five days need medical attention.

4. What should I do if I'm concerned about a fever?

When in doubt, be seen by a doctor. If you or your child require care, we welcome patients at the following locations:

  • Stamford Health Medical Group and Stamford Health Pediatric Medical Group
  • Stamford Health's Walk-In Center (patients must be 14 or older)
  • Stamford Health's Emergency Department and Stamford Health's Pediatric Emergency Department

About the Authors

Karen Justiniano, DO, MS, is a family medicine physician at Stamford Health Medical Group.

Krishnan Narasimhan, MD is Chair of the Department of Family Medicine.





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