PAMF Health Blog

Be Well, Be Well Informed

When to Worry About a Fever

Posted on Jan 21, 2014


Nearly every parent has felt their child’s hot, feverish forehead and worried. Is it serious? How high is too high? Should they go to the doctor?

Few symptoms scare parents more than fever, says Palo Alto Medical Foundation pediatrician Cara Barone, M.D.  But it’s important to know when to treat, and when to let nature take its course. Here, Dr. Barone answers parents’ most common questions about fever, and offers tips on how to take your child’s temperature properly.

What causes fever in my child?

Fever is a healthy sign the body is working properly to fight and overcome an infection.  Through a chemical reaction, our bodies elevate our core temperatures in effort to stop bad viruses and bacteria from replicating. The most common sources of infection in children are viruses. Young children can often have seven to 10 viral illnesses with fever each year – especially if they are in daycare or preschool, where viruses spread easily among children. The second most common sources of infection are bacteria. Both types of infections, viral and bacterial, can cause fevers.

We worry most about fevers in very young children – especially infants less than 3 months old – because their immune systems are still developing. This leaves them at risk for severe infections. In preschool age children and beyond, we pediatricians generally don’t worry much about fevers unless they last for four days or more, and cause symptoms such as significant listless/irritability, a bad sore throat, worsening coughing or pain with urination.

How should I take my child’s temperature?

One of the most important skills of parenting is to know how to take a temperature correctly. In babies and children less than 1 year of age, it is important to feel comfortable taking a rectal temperature. This is by far the most accurate method of taking a young child’s temperature. New parents are often frightened to take a rectal temperature. But it doesn’t hurt their baby, and it’s quite simple once you know how to do it.

Lubricate the digital thermometer with petroleum jelly and insert the silver tip of the thermometer into your baby’s rectum about 1/4 – 1/2 of an inch. Hold it gently for one minute, then remove and read the temperature. You can see illustrations showing you how to take a rectal temperature at Or, watch this video from Baby Basics.

For children older than 1 year of age, the best and most accurate methods of taking a temperature is either with an oral digital thermometer or a tympanic (ear) thermometer.  Ear thermometers are great for toddlers. They are usually accurate, but can be off if your child has lots of ear wax. You can find illustrations showing how to use an ear thermometer at

How high a fever is too high?

In infants less than 2 months of age, a fever is any temperature over 100.4º F. It’s also a concern if your newborn’s temperature is less than 96 F. For an abnormal temperature in your newborn, call your doctor or go to the urgent care clinic or emergency room — your newborn needs to be seen right away.

In babies and children older than 3 months, a fever is a temperature greater than 101.5º F. Call your doctor if your child’s temperature reaches 102.2º F or higher.

Most fevers go away in a couple of days. Call your doctor if the fever lasts four days or more. Call the doctor right away if your feverish child has vomiting or diarrhea, earache, severe abdominal pain, headache, stiff neck, sore throat, trouble breathing, pain when urinating, swollen joints, other localized pain and a purplish/dark rash that does not fade when you press on it. Also call the doctor if your child is listless or refuses to drink fluids.

Should I give my child medicine to lower her fever?

Fever-reducing medicines are not needed for low-grade fevers (99º  to 101º F) unless your child seems uncomfortable or is not drinking well. Once children’s fevers rise above 101.5º F, they generally feel miserable, and fever-reducing medicines will help them feel better. Children may be more likely to drink fluids properly after they have had fever-reducing medicines.

It is important to make sure you are giving your child the correct dose of medicine. Too little medicine won’t be effective, but too much could be dangerous. Follow the instructions on the label carefully and only use the cup or syringe that came with that medicine. (Never use a household teaspoon. They vary in size, so your dose may be wrong.)

Two types of fever medicine are safe for children: Acetaminophen (sold as Tylenol) and ibuprofen (sold as Motrin and Advil). Tylenol is the only fever-reducing medicine approved by the FDA for babies younger than 6 months old. Motrin has a few advantages over Tylenol for children older than 6 months of age: It lasts between six and eight hours; it can reduce swelling from teething and ear infections with its anti-inflammatory properties; and it may be a better choice for children who have asthma or recurrent wheezing.

It’s a good idea to print out the correct dosing for these medicines. Or bookmark the pages for easy reference:

Tylenol for children (acetaminophen) dosing chart
Motrin and Advil for children (ibuprofen) dosing chart

Remember, fevers are a sign of a healthy immune system. If your child has a low fever and no other worrisome symptoms, provide plenty of fluids, rest and love. The fever should go away in ta few days.

Barone-Cara-2013-webCara Barone, M.D. , is a pediatrician at the Palo Alto Medical Foundation.