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This is a life-threatening emergency. Call 911 immediately, then follow these steps while waiting for help.
Fever in a Newborn (Under 3 Months) — Always an Emergency
Content reviewed against published AAP, AAP, NIH guidelines
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A rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months old is ALWAYS a medical emergency. Newborns have immature immune systems and cannot fight infections effectively. Fever at this age can indicate serious bacterial infections including meningitis, UTI, or sepsis. Do not wait — go to the ER immediately.
Immediate actions
- Call 911 immediately
- Take baby's temperature rectally — this is the only accurate method for newborns
- DO NOT: Do NOT wait to see if the fever goes down on its own
Step-by-Step Response
Take rectal temperature
Use a digital rectal thermometer with petroleum jelly on the tip. Insert gently about 1/2 inch into the rectum. Wait for the beep. A reading of 100.4°F (38°C) or higher is a fever.
Do not give medicine
Do NOT give fever-reducing medicine. The ER team needs to evaluate the actual fever. Treating it may mask signs of serious infection.
Go to the ER immediately
Do not wait for your pediatrician's office to open. Do not call and wait for a callback. A fever in a baby under 3 months requires immediate ER evaluation — day or night.
Dress baby lightly
Remove excess layers. Dress in a single light layer. Overbundling can raise temperature. You want to avoid making the fever worse but do not try to cool baby with cold water.
Prepare for the ER visit
Bring: baby's insurance card, a diaper bag, the thermometer reading, a timeline of symptoms, feeding log (how much/when baby last ate), and list of any medications or supplements.
Expect testing at the ER
The ER will likely perform blood work, urine analysis (via catheter), and possibly a lumbar puncture (spinal tap) to rule out meningitis. This is standard of care — not overreaction.
Possible hospital admission
Many babies under 3 months with fever are admitted for 24-48 hours for IV antibiotics while awaiting culture results. This is protective — infections can progress rapidly in newborns.
Follow-up care
Even if all tests come back normal, follow up with your pediatrician within 24 hours of discharge. Continue monitoring baby closely for any new symptoms.
What NOT to Do
- ✕Do NOT wait to see if the fever goes down on its own
- ✕Do NOT give Tylenol (acetaminophen) to a newborn under 3 months without explicit doctor instructions
- ✕Do NOT take temperature only under the arm — this is inaccurate in newborns. Use rectal.
- ✕Do NOT bundle baby in extra blankets — this can raise body temperature further
- ✕Do NOT assume baby "just feels warm" — always confirm with a rectal thermometer
- ✕Do NOT call and wait for the doctor to call back — go to the ER directly
- ✕Do NOT give ibuprofen to any baby under 6 months
When to Seek Help
Call 911 if:
- Baby with fever is unresponsive or extremely difficult to wake
- Baby with fever is having a seizure
- Baby with fever has blue or gray skin color
- Baby with fever is having difficulty breathing
- Baby with fever has a purple or red rash that does not blanch (fade) when you press on it — this can indicate meningococcal infection
- Baby with fever has a bulging soft spot (fontanelle)
Go to ER if:
- ANY baby under 3 months (0-90 days old) with a rectal temperature of 100.4°F (38°C) or higher — no exceptions
- Baby under 3 months who is unusually irritable, lethargic, or refusing to feed even without confirmed fever
- Baby at any age with fever AND a non-blanching rash (purple/red spots that do not fade with pressure)
- Baby with fever AND bulging fontanelle (soft spot)
- Baby with fever AND persistent vomiting or inability to keep fluids down
Call your doctor if:
- Baby is 3-6 months old with a temperature of 101°F (38.3°C) or higher — call for guidance
- Baby over 3 months has a fever lasting more than 3 days
- Baby has a fever and is not feeding well
- You are unsure how to take a rectal temperature and baby feels warm
Age-Specific Guidance
0-28 days
The highest risk period. Fever in the first month of life almost always results in full sepsis workup (blood, urine, spinal fluid) and hospital admission for IV antibiotics. This is because neonatal infections can be fatal within hours if untreated.
29-60 days
Still very high risk. Most hospitals will perform a full workup. Some lower-risk babies (based on appearance and lab markers) may be managed with close outpatient follow-up, but many are still admitted.
61-90 days
Risk remains elevated compared to older infants. ER evaluation is still standard. The workup may be less extensive if baby appears well and initial labs are reassuring, but fever at this age is never dismissed.
Prevention
- Limit visitors in the first 2-3 months — newborns have immature immune systems
- Require all visitors to wash hands before holding baby
- Keep baby away from anyone who is sick (even mild cold symptoms)
- Avoid crowded places with newborns when possible
- Keep baby's immunizations on schedule starting at 2 months
- Ensure pregnant mothers receive Tdap vaccine during pregnancy (protects baby from whooping cough)
- Breastfeeding provides antibodies that help protect against infections
- Have a working digital rectal thermometer at home BEFORE baby is born
Frequently asked questions
Should I call 911 for fever in a newborn (under 3 months) — always an emergency?
What should I do first?
What should I NOT do?
How can I prevent this?
Sources
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources
Related Emergency Guides
Bottom line
This is a serious emergency. Always call 911 first, then follow the steps above while help is on the way.
You are doing the right thing by learning what to do in an emergency. Being prepared is one of the best things you can do for your child.