Baby Fever: What Parents Need to Know

Few things worry parents more than a sick baby. When your little one feels warm, your first instinct is to grab the thermometer. Then come the questions: Is this a fever? Is it serious? Should I call the doctor?

Here's what you need to know about fever in babies.

Important: This article provides general information based on AAP guidelines. Fever in infants, especially those under 3 months, requires prompt medical attention. Always call your pediatrician when your baby has a fever.

What Is a Fever?

A fever is a body temperature that's higher than normal. For babies, the AAP defines fever as:

Rectal temperature of 100.4°F (38°C) or higher.

This is the most accurate way to take a baby's temperature, especially in the first few months of life.

Normal body temperature can vary slightly throughout the day and with activity. A reading just under 100.4°F doesn't necessarily mean there's no concern. If your baby seems unwell, trust your instincts and call your doctor.

Taking Your Baby's Temperature

For babies under 3 months, rectal temperature is recommended for accuracy. Here's how:

Clean the thermometer with rubbing alcohol or soap and water. Apply a small amount of petroleum jelly to the tip. Lay baby on their back with legs lifted, or on their tummy across your lap. Gently insert the thermometer tip about half an inch to one inch into the rectum. Hold it in place until the thermometer beeps. Remove and read.

For older babies (3 months and up), other methods can be used, but rectal remains most accurate. Armpit (axillary) readings are convenient but less precise. Add about 1°F to an armpit reading for a rough estimate.

Forehead and ear thermometers can be used in older infants, but accuracy varies by device. Discuss with your pediatrician which method they recommend.

When to Call the Doctor Immediately

Call your pediatrician right away if:

Your baby is under 3 months old and has a fever of 100.4°F (38°C) or higher. This is always urgent.

Your baby is 3 to 6 months old with a temperature of 102°F (38.9°C) or higher.

Your baby is 6 months or older with a temperature of 103°F (39.4°C) or higher.

Fever is accompanied by concerning symptoms (see below).

Seek immediate medical care if your baby:

Is very sleepy or difficult to wake. Has trouble breathing. Has a rash that doesn't fade when pressed. Won't eat or drink. Has fewer wet diapers than usual. Has a stiff neck. Has a seizure. Seems extremely irritable or inconsolable.

When in doubt, call. Your pediatrician would rather hear from you with a question than have you wait when something is wrong.

Why Babies Get Fevers

Fever is usually a sign that the body is fighting an infection. Common causes include:

Viral infections: Colds, flu, and other viruses are the most common cause of fever in babies.

Bacterial infections: Less common but can be more serious. These include ear infections, urinary tract infections, and others.

Vaccines: Low-grade fever is a normal response to some vaccinations.

Overdressing: Babies can overheat from too many layers. This isn't a true fever. Removing layers should bring temperature down quickly.

Your pediatrician can help determine the cause and whether treatment is needed.

Caring for a Feverish Baby

If your pediatrician says you can manage the fever at home:

Keep baby hydrated: Offer breast milk or formula frequently. Babies lose fluids faster with fever.

Dress lightly: Don't bundle a feverish baby. Light clothing helps release heat.

Keep the room comfortable: Normal room temperature, not too hot or cold.

Monitor symptoms: Watch for changes in behavior, feeding, or new symptoms.

Fever medication: Your pediatrician may recommend infant acetaminophen or ibuprofen (ibuprofen only for babies 6 months and older). Never give aspirin to babies or children. Always follow dosing instructions exactly and use the measuring device that comes with the medication.

Never give fever medication to a baby under 3 months without talking to your doctor first.

What Fever Tells Us

Fever itself isn't usually dangerous. It's the body's natural response to infection. A higher fever doesn't necessarily mean a more serious illness. Some minor viruses cause high fevers, while some serious infections might cause only low-grade fever.

What matters more than the number is how your baby is acting. A baby with 101°F who is feeding well and responsive is often less concerning than a baby with 99.5°F who is lethargic and won't eat.

Tracking Temperature

When your baby is sick, tracking temperature over time is helpful. Note:

The time of each reading. The temperature. The method used (rectal, armpit, etc.). Any medication given and when.

This information helps you see whether fever is trending up or down, and it's valuable to share with your pediatrician. You won't have to try to remember details during a stressful call.

Febrile Seizures

Some children have seizures triggered by fever, called febrile seizures. These are scary to witness but usually not harmful. They're most common between 6 months and 5 years.

If your baby has a seizure: lay them on their side, don't put anything in their mouth, and time the seizure. Call your pediatrician immediately or seek emergency care if the seizure lasts more than 5 minutes.

If your baby has had a febrile seizure, your pediatrician will advise you on management for future fevers.

Trust Your Instincts

You know your baby. If something seems wrong, even if you can't pinpoint it, call your doctor. "My baby just doesn't seem right" is a valid reason to seek advice.

Pediatricians and nurses are there to help. They don't mind questions, and they'd much rather you call than worry alone.

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BabyZone helps you track symptoms including temperature readings, making it easy to share accurate information with your pediatrician.

This article is for informational purposes only and does not constitute medical advice. Always contact your pediatrician when your baby has a fever.