If your baby wakes up in the middle of the night crying and feeling flushed, you’ll need to take their temperature to determine if they have a fever. There are many reasons why your little one might develop a fever.

While fevers themselves aren’t dangerous, sometimes the underlying cause can be. Young infants are more likely than older children to have a cause for their fever that requires treatment.

Newborns — ages 3 months and younger — should be seen by a doctor immediately for any fever.

Infants 3 months and older with low-grade fevers can be treated at home with proper care if no other concerning symptoms develop. Infants with persistent or high fevers should be assessed by a doctor.

Normal temperature hovers somewhere close to 98.6°F (37°C). This temperature can vary slightly from morning to evening. Body temperatures are generally lower when you wake up and higher in the afternoon and evening.

Infants under 3 months old with a fever require immediate medical attention to diagnose the underlying cause and treat it if necessary.

Infants are considered to have a fever if their temperature is:

  • 100.4°F (38°C) or higher when taken rectally
  • 99°F (37.2°C) or higher when taken by other methods

Low-grade fevers don’t always require a visit to your doctor for infants older than 3 months.

A slightly elevated temperature in an infant older than 3 months may not require a trip to the doctor. You may be able to treat the fever at home with the following methods:

1. Acetaminophen

If your child is over 3 months, you can offer them a safe amount of children’s acetaminophen (Tylenol).

Doses are usually based on weight. Your doctor may recommend weighing your baby if they haven’t recently been weighed or if they’ve had a recent growth spurt.

If your baby isn’t uncomfortable or fussy from their fever, you may not need to give them any medication. For higher fevers or other symptoms that are making your infant uncomfortable, medication can help them temporarily feel better.

2. Adjust their clothing

Dress your infant in lightweight clothing and use just a sheet or light blanket to keep them comfortable and cool.

Overdressing your infant may interfere with their body’s natural methods of cooling down.

3. Turn down the temperature

Keep your home and your infant’s room cool. This can help prevent them from overheating.

4. Give them a lukewarm bath

Try sponging your baby down with lukewarm water. (Water temperature should feel warm, but not hot, to the touch on your inner arm.) Maintain constant supervision during bathing to ensure water safety.

Avoid using cold water, as this can lead to shivering, which may increase their temperature. Dry your baby off immediately following the bath and dress them in lightweight clothing.

Alcohol baths or wipes to lower fevers aren’t recommended and can be harmful.

5. Offer fluids

Dehydration is a possible complication of fever. Offer regular fluids (breast milk or formula) and make sure your baby has tears when crying, a moist mouth, and regular wet diapers.

Call your doctor’s office to discuss ways to keep your child hydrated if this is a concern.

There are several things you should not do if your infant has a fever:

  • Do not delay medical attention for a newborn with any fever or an infant with a persistent fever or who seems very ill.
  • Do not administer medication to your infant without first checking their temperature and consulting your doctor’s office.
  • Do not use medication intended for adults.
  • Do not overdress your infant.
  • Do not use ice or rubbing alcohol to lower your infant’s temperature.

To get the most accurate temperature, use a digital multiuse thermometer rectally. Keep in mind that a rectal temperature will be higher than temperatures taken with other methods.

Here’s how to take your infant’s temperature rectally:

  • Read the manufacturer’s instructions initially and set the measurements to either Fahrenheit or Celsius (in order to report the temperature correctly).
  • Clean the thermometer with rubbing alcohol or soap.
  • Coat the end of the thermometer in petroleum jelly or another safe lubricant.
  • Remove any clothing or diaper from your infant’s bottom.
  • Lay your infant on their stomach on a safe and comfortable surface, such as a changing table or bed, or on your lap.
  • Hold your infant gently in place while you take the temperature. Don’t let them move or wiggle during the process to avoid the thermometer moving further into your infant’s rectum. Having someone’s help to hold the infant still is best to prevent injury.
  • Turn on the thermometer and insert it only a half inch to 1 inch into your infant’s rectum until the thermometer beeps. (Most thermometers have a visual notch or safety guide that demonstrates a safe limit for rectal insertion.)
  • Pull out the thermometer carefully and read the temperature.

Other devices may provide accurate temperature readings for your infant if you use them according to their instructions.

Temporal artery thermometers measure the temperature from the forehead and may not work for infants younger than 3 months old. A rectal temperature is recommended for infants of this age group.

Tympanic thermometers read the temperature from a baby’s ear and should only be used in infants 6 months and older.

Here are a few other guidelines for taking your infant’s temperature:

  • Designate your digital multiuse thermometer for rectal use only and label it to avoid confusion.
  • Avoid taking your infant’s temperature orally or under the armpit. These aren’t considered accurate for infants and young children.
  • Don’t conclude that your infant has a fever if you feel warmth by touching their forehead. You need an accurate digital thermometer reading to determine fever.
  • Avoid using mercury-filled thermometers. They pose a risk of mercury exposure if they break.

Make sure to monitor your infant’s temperature during the course of an illness and observe other symptoms and behaviors to determine whether you should contact your doctor.

You should contact your infant’s doctor or seek medical treatment if:

  • your infant under 3 months old develops any elevation in temperature
  • your infant between 3–6 months old has a rectal temperature of 102°F (38.9°C) or higher
  • your 6- to 24-month-old has a fever above 102°F (38.9°C) for more than a day or two with no other symptoms
  • they have a fever that has lasted longer than 24 hours or that occurs regularly
  • they’re irritable (very fussy) or lethargic (weak or more sleepy than usual)
  • your infant’s temperature doesn’t lower within an hour or so after taking an appropriate dose of medication
  • they develop other symptoms like a rash, poor feeding, or vomiting
  • they’re dehydrated (not producing tears, spit, or the usual amount of wet diapers)

Fevers are generally a symptom of a larger medical condition.

Your infant may develop a fever for many reasons, including from:

  • a viral infection
  • a bacterial infection
  • certain vaccinations
  • another medical condition

Common causes of fevers in children include respiratory illnesses like colds and ear infections.

Does teething cause fevers?

Teething isn’t considered a cause of fever. It may be that your teething infant has another underlying condition causing the fever.

Treating a fever in an infant will vary based on the age of the child and the symptoms surrounding the fever.

Newborns must be seen by a doctor immediately if they develop a fever, while older infants may be treated at home if they develop a mild fever.

Always check with your doctor before giving any medication to your infant, and see a doctor if your child develops a high fever or if the fever lasts longer than a day or two.