Baby Fever Guide: Temperature Ranges, Home Care & When to Call the Doctor
What's a normal baby temperature, how to measure it accurately, what you can do at home, and the warning signs that require an immediate doctor or ER visit.
A baby who feels hot is every parent's alarm trigger. Fever is the body's normal immune response to infection — but in babies, especially newborns, the threshold for concern is much lower than in older children or adults. Knowing the numbers and the warning signs keeps you prepared without panicking at every warm forehead.
What's a Normal Temperature and When Is It a Fever?
- Normal: 36.5–37.5°C (97.7–99.5°F)
- Low-grade fever: 37.5–38.0°C (99.5–100.4°F)
- Fever: 38.0°C (100.4°F) or higher (rectal measurement)
- High fever: 39.0°C (102.2°F) or higher
How to Measure Temperature Accurately
Different measurement methods give different readings. Knowing the offset helps you interpret results correctly.
- Rectal: Most accurate; recommended for newborns under 3 months
- Ear (tympanic): Fast and practical; more reliable after 3 months when the ear canal is larger
- Armpit (axillary): Easy but typically reads 0.5–1°C lower than actual core temperature
- Forehead (temporal artery): Convenient but higher variability
⚠️ ⚠️ A rectal temperature of 38.0°C (100.4°F) or higher in any baby under 3 months is a medical emergency. Go to the ER immediately — regardless of how the baby looks or acts. The risk of serious bacterial infection at this age is high.
Home Care for Fever
Not every fever requires medication. A temperature under 38.5°C that isn't causing obvious discomfort can be monitored. If the baby is uncomfortable, age-appropriate fever reducers can help.
- Dress in lightweight, breathable clothing
- Offer frequent nursing or formula to prevent dehydration
- Lukewarm sponge bath (36–37°C water) if very uncomfortable
- Acetaminophen (Tylenol/Paracetamol): appropriate for all ages over 3 months, dosed by weight (10–15mg/kg every 4–6 hours)
- Ibuprofen: only for babies 6 months and older
When to Call the Doctor or Go to the ER
- Under 3 months + any rectal temp 38.0°C (100.4°F) or above
- 3–6 months + temperature 39.0°C (102.2°F) or above
- Any age + temperature 40.5°C (104.9°F) or above
- Febrile seizure (convulsion) occurs
- Baby is unusually lethargic or unresponsive
- Fever lasting more than 3 days
- Fever with a rash, difficulty breathing, or stiff neck
Important Safety Note
Never give aspirin to a baby or child — it's associated with Reye's syndrome, a rare but dangerous condition. Don't alternate fever reducers on a schedule or give them more frequently than directed.