Baby Fever: When to Call the Doctor
Medically reviewed by Safi Ullah Khan
Medically reviewed by Safi Ullah Khan · Written by Muneeb Rana · Last updated 21 October 2026
Quick answer: Baby fever: for a baby under 3 months (12 weeks), call your doctor right away for a temperature of 100.4°F (38°C) or higher (AAP). At any age, call if your baby looks very ill, is unusually drowsy, has breathing trouble, a rash or a seizure, or fever repeatedly tops 104°F (40°C).
TL;DR
- Under 3 months: 100.4°F (38°C) or higher, call now.
- Any age: call if baby looks very unwell.
- Under 2 years: call if fever lasts over 24 hours.
Knowing the baby fever rules by age makes a scary moment simpler. This page follows AAP HealthyChildren and NHS guidance.
When to call, by age
| Age | Call your doctor right away if | Source |
|---|---|---|
| Under 3 months | Temperature 100.4°F (38°C) or higher | AAP |
| 3-6 months | Temperature 102.2°F (39°C) or higher (NHS), or any fever with other symptoms | NHS |
| Under 2 years | Fever lasts more than 24 hours | AAP |
| Any age | Fever over 104°F (40°C) repeatedly; looks very ill, drowsy or very fussy; stiff neck, breathing trouble, rash, repeated vomiting; a seizure | AAP |
Call emergency services if your baby is struggling to breathe, is floppy or unresponsive, has blue lips, or has a rash that doesn't fade under a glass.
How to take a baby's temperature
For babies under 3 months, a rectal digital thermometer is most accurate in the US; the NHS recommends an under-arm digital thermometer for babies under 5. Don't rely on forehead strips.
Fever after vaccines
A mild fever can follow vaccines. Under 3 months, still call. See the baby vaccine schedule.
Medicine for fever
Fever itself isn't dangerous; comfort and fluids matter most. The AAP says acetaminophen shouldn't be given to children under 2 without a doctor's guidance, and ibuprofen not under 6 months unless your doctor advises. Read how to give baby medicine.
What to log
Write down temperature readings with times, any medicine with dose and time, feeds and wet diapers. Tot's vaccine and medicine log records dose and time; feeds and diapers sit alongside. This helps your doctor and prevents double-dosing between caregivers.
Related: teething · newborn first week · baby age calculator · newborn diaper count
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Sources
- AAP HealthyChildren.org: When to Call the Pediatrician, Fever: www.healthychildren.org (accessed 21 October 2026)
- NHS: Fever in children: www.nhs.uk (accessed 21 October 2026)
- AAP HealthyChildren.org: Acetaminophen Dosing Tables for Fever and Pain: www.healthychildren.org (accessed 21 October 2026)
- AAP HealthyChildren.org: Ibuprofen Dosing Table for Fever and Pain: www.healthychildren.org (accessed 21 October 2026)
Medical disclaimer:
Tot and this website give general information only. Feeding, sleep and growth ranges vary; always follow your pediatrician's advice. If your baby is unwell, contact your doctor or emergency services.
FAQ
What temperature is a fever in a baby?
100.4°F (38°C) or higher.
Is 99.5°F a fever in a baby?
No, that's within the normal range.
Should I wake my baby to give fever medicine?
Usually not; rest matters. Follow your doctor's advice.
Does teething cause fever?
Not a true fever. Treat a fever as a sign of illness.
When is fever an emergency?
Breathing trouble, floppiness, a non-fading rash, a seizure, or a baby under 3 months with 100.4°F or more.
Related guides
Track this in Tot
Tot is a free baby tracker app for iPhone and Android that logs breastfeeding, bottle feeds, sleep, diapers, growth, vaccines and medicine, and lets parents share the log with a partner or caretaker.
