Overview
Young babies can have serious infections with only a fever.
Too many layers can raise temperature; recheck after unbundling.
Symptoms
Common signs:
- Fever in a baby under 3 months
Look up a symptom: Fever
When to get medical care
Call 911A baby who is limp, hard to wake, struggling to breathe, or has blue or gray lips: call 911. Any fever 100.4°F or higher under 3 months: go to the ER.
Get care todayA baby 3 to 6 months with fever over 102°F, or any baby who seems sick.
See a doctor soonQuestions about how to take a baby's temperature.
Causes
Infections.
Does it spread or run in families?
- Yes, it can spread from person to person.
- How it spreads: usually your own gut bacteria, getting into the urinary tract, the blood, the belly, or mother to baby around birth.
- Washing hands often and staying home when sick help protect others.
Diagnosis
Babies are checked in the ER.
Tests
Tests, if needed:
- Blood and urine tests:
- Spinal tap: Sometimes.
Treatment
Go in.
Self-care
- Take a rectal temperature
- Call your baby's doctor or go to the ER
- Don't bundle a baby with fever
Which doctor treats this
- Emergency doctors treat it first, in the ER.
- They may send you to a pediatric specialist: an infectious disease specialist, for hard-to-treat infections.
Back to school, work, or sports
- Keep your child home until they've had no fever for 24 hours without fever medicine and feel better.
- For the next few days, wash hands often and teach them to cough into an elbow.
Children, pregnancy, and older adults
- Under 1 month: Always admitted for tests.
For caregivers
- Learn the warning signs and when to call the doctor or 911.
- Keep a list of your child's medicines, doses, and doctors on your phone.
- Tell teachers, coaches, and sitters what to watch for and what to do.
- Learn CPR. Many hospitals and the Red Cross offer classes.
- Take breaks and ask for help. Caregivers need care too.
Outlook
Fast care leads to good outcomes.
Getting ready for your visit
Bring a list of your symptoms and medicines.
Questions to ask
- How do I take a rectal temperature?
Research studies
Research studies test new ways to find and treat health problems. Some are looking for volunteers. Talk with your doctor before joining one.
Search ClinicalTrials.gov for studies on Fever in a newborn (under 3 months)
Sources
Last updated 2026-11-12.