Newborn Fever: When to Worry and When to Call
There is one number to memorise for a newborn: 38°C.
In a baby younger than three months, a temperature of 38°C or higher is treated as an emergency every time, no matter how well the baby seems. Babies can be seriously unwell and still look alert.
This page covers that, the other signs that need urgent help even without a fever, and what to do while you arrange care.
Quick answer
When is a newborn fever urgent?
Contact urgent medical care immediately if a baby under three months has a temperature of 38°C or higher. Also seek urgent help for breathing difficulty, blue or grey coloring, unusual difficulty waking, or feeding changes with signs of illness.
Key takeaways
- 38°C or higher under three months = urgent assessment now, every time.
- Breathing difficulty, blue or grey coloring, or difficulty waking = emergency, with or without a fever.
- Do not bring the temperature down with paracetamol or ibuprofen before being seen.
The threshold: 38°C under three months
| Age | Temperature | What to do |
|---|---|---|
| Under 3 months | 38°C / 100.4°F or higher | Urgent medical assessment now — do not wait to see if it settles |
| Under 3 months | Below 38°C but you are worried | Contact your clinician the same day; do not dismiss it because there is no fever |
| 3-6 months | 38°C or higher | Contact your clinician the same day; urgent care if unwell or not feeding |
| Over 6 months | 38°C or higher | Contact your clinician; urgent care if there is breathing difficulty, dehydration, or a rash that does not fade |
The under-three-month rule is not a guideline. It is the point at which clinicians do not wait and see, because a newborn's temperature can rise quickly and a serious infection can look like ordinary tiredness in the early hours.
A temperature under the arm is the reading most health services ask you to take in a young baby, because it reads closer to the body's core. Follow the instructions your own clinician has given you about which thermometer and which site to use — those instructions outrank anything on this page.
Other signs that need urgent help, even without a fever
A baby who is hard to wake, is breathing oddly, or is blue or grey needs emergency care immediately. Do not wait for a temperature reading before seeking help.
What to do while you arrange care
Before you leave
- Take the temperature again so you can tell the clinician when it started
- Note when the baby last fed, and how much
- Count wet diapers since this morning
- Take a photo or video if the behaviour worries you — you may not be able to describe it accurately once you are stressed
- Bring the feeding log if you keep one
Do not
- Do not give paracetamol or ibuprofen to bring the temperature down before you are seen
- Do not wait for the fever to break on its own
- Do not rely on a home test result if the baby seems unwell
- Do not use leftover antibiotics from a previous illness
The most common reason newborns are seen urgently turns out to be nothing serious. That is not a reason to wait — it is the reason the threshold is set where it is.
Breastfed babies and fever
Fever is separate from feeding, and a baby can feed well and still be fevered. Equally, feeding poorly with no fever still deserves a call in the first weeks.
CDC guidance notes that breastfed newborns commonly feed 8 to 12 times in 24 hours, and that fewer than six wet diapers per day by day five can indicate insufficient intake. Those are feeding benchmarks, not fever thresholds — if there is a fever, the 38°C rule above applies regardless of how well the baby is feeding.
Sources
- How often and how much to breastfeed a newbornCDC
Most newborns need to breastfeed 8 to 12 times every 24 hours.
https://www.cdc.gov - Urgent and emergency symptoms in pregnancy and after birthNHS
If you experience heavy vaginal bleeding, severe headaches, chest pain, difficulty breathing, or sudden changes in your baby's movements, contact your maternity triage line or local emergency services immediately.
https://www.nhs.uk/nhs-services/urgent-and-emergency-care-services/Link checked 2026-10-14 - Reduce the risk of sudden infant death syndrome (SIDS)NHS
Always place your baby on their back to sleep in the feet-to-foot position. Place your baby in a separate cot or Moses basket in the same room as you for every sleep for at least the first 6 months. Use a firm, flat mattress, and keep your baby's cot clear of anything that could cover their face and head – do not use pillows, duvets, cot bumpers, loose blankets, soft toys or anything to keep your baby in place, like pods or nests.
https://www.nhs.uk/baby/caring-for-a-newborn/sudden-infant-death-syndrome-sids/Link checked 2026-10-15