Newborn Fever: When should I worry?

Article at a Glance

• A baby’s first fever can cause a lot of stress, but knowing to take the proper procedures will help.
• Common symptoms of a fever include: fussy behavior, difficulty in sleeping, difficulty in eating, and more.
• Depending on the age of your baby, a different method of temperature reading may be necessary.

Becoming a new parent can feel joyous but also a bit overwhelming. It’s normal to worry and overanalyze every little change in your baby. Believe us when we say that every parent has had to adjust to the rollercoaster of caring for a newborn. 

Because newborn babies are fragile and still developing, they also have an immature immune system. This makes them more susceptible to infections and they can often get fevers while their little bodies fight viruses and germs. 

If you suspect that your newborn is sick and may have a fever, you can use this article to help you: 

• Identify the symptoms of an infant with a fever. 
• Eliminate other reasons that your infant may have fever symptoms. 
• Learn what temperature an infant should be and how to take their temperature.  
• Confirm whether or not your child is old enough for fever medications. 
• Know when to call your pediatrician.

What are the symptoms of an infant with a fever? 

When a newborn has a fever, they experience symptoms similar to adults. A fever may give the newborn a headache, body aches, and an increased heart rate or breathing rate. Some outward indicators of a sick infant are if they: 

• Are fussier than usual 
• Can’t seem to be comforted or settled down 
• Are flush in the face, red, and sweaty 
• Are not sleeping well 
• Are not eating or can’t keep food down 
• Don’t want to interact, play, or acknowledge you 
• Seem distant or lethargic 
• Are shivering or seem to have the chills 
• In severe circumstances, newborns may have convulsions or even seizures. If this happens to your newborn, call 9-1-1 immediately and follow up with your child’s pediatrician. 

Other Reasons Your Infant May Show Signs of a Fever 

Unless your newborn is experiencing severe fever symptoms, there could be a few other reasons your infant shows fever-like symptoms. A flush-faced, fussy, and inconsolable newborn could be: 

1. Overheated and can experience chills with the heat as well. Try to keep your home around 72-75 F, keep them clothed comfortably and to the level of clothes you are wearing yourself, and keep them away from heat sources. 
2. Dehydrated – Learn more about dehydration here. 
3. Reacting to a recent vaccination.

What Temperature is Considered a Fever? 

According to the Mayo Clinic and the AAP, the appropriate temperature of an infant should be between 97.9 F to 100.4 F. These organizations also recommend using a digital thermometer for the reading, which can be done by rectum, armpit, or mouth, depending on age. Do not use an ear thermometer to check an infant’s temperature.

How to Take a Newborn, Infant, and Toddler’s Temperature: 

Newborns up to 3 months old: 

• Research shows that a rectal temperature reading is the most accurate for newborns.  
• To take a rectal temperature: 

1. 1. Make sure the digital thermometer is clean using soap and water or an alcohol wipe. 
   2. Lay your newborn on their back like you’re changing their diaper. 
   3. Put some petroleum jelly on the bulb of the thermometer. 
   4. Tuck the baby’s knees towards their chest and gently insert the thermometer into their rectum. Do not go more than an inch and stop if met with resistance. 
   5. Wait for the bleep of the thermometer to indicate it took the reading and gently pull it out.  

• If the thermometer reading is higher than 100.4 F, it is considered an emergency, and you should contact your doctor immediately. 

Infant from 4 to 6 months old: 

• A rectal reading will be the most accurate. However, The Mayo Clinic also states that an armpit reading would work as well. 
• To take an armpit reading, you will: 

1. 1. Make sure the digital thermometer is clean using soap and water or an alcohol wipe. 
   2. Place the bulb of the thermometer in the center of the infant’s armpit. 
   3. Then close their arm against their body, so the thermometer stays in place.  
   4. Wait about a minute for the bleep and remove the thermometer from under their arm. 

• If the infant’s temperature is 100.4 to 102 F, call your doctor. But if the temperature is higher than 102 F, seek medical help immediately. 

Children from 6 to 24 months old: 

• You can choose any of the digital thermometer reading methods, including oral, armpit, or rectal. 
• If the temperature is near 102 F with no other signs of illness, you can wait a day to see if the fever breaks. 
• However, if their temperature is near 102 F AND they show fever symptoms, you should call your doctor.  
• Any fever over 102 F is considered an emergency, and you should seek medical attention. 

Can I Give My Infant Medicine for a Fever? 

Newborns and infants up to 5 months old: 

• Cannot receive ibuprofen. 
• Consult your doctor before giving a newborn any medication. 

Children from 6 to 24 months old: 

• It is safe to give them acetaminophen to see if it helps reduce or break the fever. 
• However, make sure to check the Tylenol or other acetaminophen product and only provide the child with the appropriate dosage for their age. 

When to Call the Doctor? 

It is always a safe bet to call your doctor if your newborn is running a fever.  

Your pediatric care team will probably ask: 

• When did you start to notice your newborn was sick? 
• What symptoms are they experiencing? 
• What was their last temperature reading?  
• When was the last time the newborn ate? 
• Is your newborn vomiting, having diarrhea, seizures, or convulsions? 

Again, if your newborn, infant, or toddler is having convulsions or seizures, call 9-1-1.

Newborn fevers can be frightening for new parents, but your pediatric care team is here for your concerns 24/7. Call us anytime for guidance, to arrange an after-hours visit, or to make an appointment. 

Reviewed on January 1, 2022 by:

Matt Allen, D.O.
Board-certified Pediatrician

Dr. Allen enjoys trivia, sports, and caring for his four kids. He’s passionate about children’s physical and mental health and has personal experience with parenting multiples.

Saratoga Springs Office

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