Fever in babies: when it is an emergency

For a baby younger than 3 months, the AAP’s threshold is clear: a temperature of 100.4°F (38.0°C) or higher is a reason to call the pediatrician straight away, at any hour. For older babies and toddlers the number matters less than how the child looks and acts, and a short list of signs means calling right away rather than waiting for morning. A fever itself is usually a sign the body is responding to an illness, and most of them are handled at home with a phone call for guidance.

Around this age

A fever is generally a temperature of 100.4°F (38°C) or higher. How you take it changes what the number is worth: the AAP says a rectal reading gives the best measurement, especially for infants under 3 months, a forehead thermometer can be used at any age, an ear thermometer works from 6 months because younger babies’ ear canals are too narrow, and an oral reading is not recommended until about age 4. An armpit reading is the least accurate and is used for screening.

MedlinePlus gives thresholds by age for contacting a health care provider: a rectal temperature of 100.4°F (38°C) or higher in a baby younger than 3 months, and a fever of 102.2°F (39°C) or higher in a baby 3 to 12 months old.

Duration counts too. The AAP suggests calling if a fever lasts more than 24 hours in a child younger than 2 years, or more than 3 days (72 hours) in a child 2 years or older. MedlinePlus puts the equivalent line at a fever lasting longer than 48 hours in a child under 2.

What families usually do

Take the temperature before you call, and write down the number, the time, and which method you used. On the phone, “102.2 rectal at 4 a.m., 101 at 8 a.m.” is more useful than “hot all night”.

Keep an eye on drinking and wet diapers. Fluids and rest are the ordinary home measures; if you are considering fever medicine, the amount depends on your child’s weight and age, so ask your pediatrician or pharmacist rather than guessing from the box.

Watch how your baby looks between temperature spikes rather than only the number. A baby who is drinking, has wet diapers, and settles when comforted reads differently than one who stays limp after the fever eases.

Newborns are the exception to all of this. In the first 3 months a fever can be serious, and these babies are seen quickly regardless of how well they seem.

When to call your pediatrician

Call right away, at any age, if your child:

• is younger than 3 months (12 weeks) and has a temperature of 100.4°F (38.0°C) or higher
• looks very ill, is unusually drowsy, or is very fussy
• has a stiff neck, a severe headache, severe sore throat, severe ear pain, breathing difficulty, an unexplained rash, or repeated vomiting or diarrhea
• has had a seizure
• has been in a very hot place, such as an overheated car
• has immune system problems, such as sickle cell disease or cancer, is taking steroids or other medicines that affect the immune system, or has heart problems that affect how they tolerate a fever
• has a temperature that rises above 104°F (40°C) repeatedly, at any age

MedlinePlus lists signs that call for emergency care, which means 911 or your local emergency number: a child who cannot be calmed or cannot be woken, is confused, cannot walk, has trouble breathing, has blue lips, tongue or nails, has a stiff neck or severe headache, refuses to move an arm or leg, has a seizure, or has new bruises or a new rash.

Anything that worries you is reason enough to call, including a fever that fits none of these lines. Your pediatrician’s office knows your child’s history, and after-hours advice is part of what the practice does.

Sources

• Fever: When to Call the Pediatrician — HealthyChildren.org (AAP)
• When your baby or infant has a fever — MedlinePlus (NIH)
• How to Take Your Child’s Temperature — HealthyChildren.org (AAP)

This is educational information from public sources, not a replacement for advice from your child’s healthcare professional.

In Withya, the temperature you took at 3 a.m. goes into Care with the time and the adult who took it, so whoever calls the office next has the whole night in front of them.