Quick Answers
A fever in a baby under 3 months old should be evaluated by a doctor right away. For babies 3-6 months old, call the doctor if the fever is over 100.4°F. Babies over 6 months can usually be monitored at home for fevers under 102°F. Seek immediate medical care if the baby has a fever over 104°F, along with other symptoms like inconsolable crying, trouble breathing, or refusal to eat or drink.
What is Considered a Fever in Babies?
A normal body temperature for babies is considered 97.7–99.5°F when taken rectally. A fever is technically defined as:
- 100.4°F or higher when taken rectally
- 99°F or higher when taken orally
- 100°F or higher when taken under the arm
Rectal temperatures give the most accurate reading for babies under 3 months. For older babies, temperature can be taken by rectum, mouth (using a pacifier thermometer), ear, forehead, or under the arm. However, oral and ear temperatures are slightly less accurate.
When to Seek Emergency Care
Take your baby to the emergency room right away if they have any of the following:
- Fever over 104°F
- Fever over 100.4°F in a baby under 2 months old
- Fever over 100.4°F along with other concerning symptoms like inconsolable crying, trouble breathing, refusing to eat or drink, neck stiffness, rash, or seizures
- Fever that persists over 24 hours in a baby under 2 months old
- Fever that persists over 3 days in any age baby
- Fever in a baby that looks very ill, pale, overly sleepy, difficult to wake up, or limp
Fevers this high or with any of these accompanying symptoms can signal a serious infection like meningitis, pneumonia, or sepsis. These require prompt medical treatment so always take the baby to the ER or call 911.
When to Call the Doctor
Call your pediatrician right away if your baby 3-6 months old has a fever over 100.4°F. Also call for a fever over 102°F in babies over 6 months old. Describe all of your baby’s symptoms in detail. The doctor may have you come into the office to get checked or go directly to the ER.
Other times to call the doctor include:
- Fever lasting over 24 hours in a baby over 2 months old
- Fever lasting over 3 days in any age baby
- Fever without other symptoms in babies under 3 months old
- Fever with other symptoms like cough, congestion, sore throat, rash, vomiting, diarrhea, etc.
- Your baby seems very irritable, excessively sleepy, or lethargic
The doctor can help determine if your baby needs to be seen or if home treatment is appropriate. Always call for any concerns about your baby’s fever.
When to Monitor at Home
For babies over 3 months old, fevers up to 102°F can often be safely monitored at home. However, follow up with the doctor if the fever lasts more than 3 days or is accompanied by other symptoms. Watch for any signs your baby is getting worse like increased irritability, extreme sleepiness, or trouble breathing.
To monitor a fever at home:
- Check the temperature every 2-3 hours
- Dress the baby lightly in just a diaper or light pajamas
- Offer frequent breastfeeding or bottle feeding
- Provide lots of cuddles and comfort measures
- You can give acetaminophen or ibuprofen if over 6 months old
- Encourage the baby to drink extra fluids
Call the doctor if the fever spikes over 104°F or your baby seems ill. Trust your instincts and never hesitate to get medical care if concerned.
What Causes Fevers in Babies?
Fevers in babies are usually caused by infections. Common sources include:
- Viral infections like cold, flu, SARS-CoV-2
- Bacterial infections like ear infection, urinary tract infection, pneumonia, meningitis
- Vaccine reactions – fevers after DTaP and MMR vaccines are common
- Teething – low grade fevers around 100-101°F can happen
- Heat stroke if overheated from environment or clothing
In newborns, fevers can also be caused by an inflammatory response to maternal antibodies or medicines given to the mother before delivery.
Babies tend to run higher fevers compared to older children and adults, so fevers should never be dismissed or ignored in infants.
Risk Factors for Fever
Certain factors raise a baby’s risk of developing a fever requiring medical treatment. These include:
- Age – newborns are at higher risk
- Premature birth
- Weakened immune system
- Chronic health conditions
- Not fully vaccinated
- Attending daycare – increased exposure to illnesses
- Exposure to infections from caregivers or family members
Pay extra attention for fevers in high risk babies and call the doctor right away if any fever develops. Have a low threshold for seeking emergency care when needed.
Dangers of High Fevers
Fevers don’t directly cause harm, but very high uncontrolled fevers can lead to problems like:
- Febrile seizures – convulsions brought on by a sudden spike in temperature
- Dehydration – babies lose more fluids from fever and fast breathing
- Altered mental status – extreme sleepiness, difficulty to arouse, or limpness from fever effects on the brain
- Severe illness – high fevers may reflect uncontrolled infection
- Fever-related rash – roseola, scarlet fever, Kawasaki disease
While scary, febrile seizures are generally harmless if the fever can be quickly controlled. Dehydration can usually be prevented with extra fluids. But altered mental status or uncontrollable, extremely high fevers may require hospitalization for monitoring and treatment.
Treating Fevers at Home
For babies over 6 months old, fevers 102-104°F can often be treated with measures like:
- Infant acetaminophen (Tylenol) – follow dosing instructions carefully
- Ibuprofen for babies over 6 months – follow dosing instructions
- Lukewarm baths – not too cold!
- Light clothing and bedding
- Plenty of fluids and breastfeeding
- Cool compresses on the forehead, neck, and armpits
Never give aspirin to babies or children. Rotate acetaminophen and ibuprofen doses every 3 hours. Stop any medication that seems to cause rash or trouble breathing.
Home treatment measures plus doctor guidance can help keep most moderately high fevers under control. But always watch for signs your baby is getting worse and needs medical treatment.
When Fever Requires Hospitalization
In some cases, fevers and their underlying causes require hospitalization for treatment. This is needed if the baby shows:
- Fever over 104°F not responsive to home treatment
- Signs of dehydration – no wet diapers, sunken eyes, extreme sleepiness
- High fever with stiff neck that indicates possible meningitis
- Difficulty breathing or blue color to lips and nails
- Febrile seizures longer than 5 minutes
- Inability to keep medications down due to vomiting
- No improvement in fever or symptoms over 24-48 hours
Hospital care allows close monitoring of vital signs, fluids, and mental status. Testing can determine if infections like meningitis or sepsis are present. Intravenous fluids, oxygen, seizure medications, antibiotics, and antiviral or antifungal treatments may be given as needed.
With intensive care, most babies with serious fevers fully recover. Pay close attention and don’t delay needed emergency or hospital care.
When to Return to the Doctor
Call or return to the doctor if any of the following happen after a fever:
- Fever comes back after going away for over 24 hours
- Fever persists over 3 days without improvement
- New symptoms develop like rash, sore throat, ear pain
- Breathing problems, extreme sleepiness, or poor feeding develop
- Your baby seems very ill, excessively irritable, or has convulsions
- Home treatment stops helping lower the fever
A fever that persists, returns, or worsens may require additional treatment or a change in medications. New symptoms may indicate development of a bacterial infection after a viral illness. Always call for ongoing fever, and return promptly if your baby seems ill.
Preventing Fevers
Some tips to help prevent fevers and infections in babies include:
- Breastfeed exclusively for 6 months to give immunity factors
- Ensure your baby receives all recommended vaccines on schedule
- Wash hands often, avoid sick contacts
- Never give aspirin or NSAIDs before 6 months old
- Discuss prevention with the doctor if your baby was premature or has medical conditions
- Call your doctor right away at the first sign of illness
While not every fever can be prevented, many can be avoided with good hygiene, immunizations, health precautions, and early medical care when sick.
Conclusion
Fevers require an urgent call or trip to the doctor in babies under 3 months old. For older babies, fevers up to 102°F can often be managed at home with monitoring, fluids, and alternating acetaminophen and ibuprofen if over 6 months old. Seek emergency care for high fevers over 104°F, as well as any fever with breathing trouble, extreme irritability or lethargy, or other concerning symptoms. With vigilant supervision and prompt medical care when indicated, most fevers can be managed safely and effectively.