Baby Fever: When to Worry and What to Do

A fever is one of the scariest things for a new parent — but a fever itself isn't an illness. It's a sign your baby's body is doing its job and fighting something off. Knowing the real warning lines makes it far less frightening.

Fever rarely comes alone — know the signs of dehydration, what helps a baby's first cold, and the full list of warning signs to call the doctor.

What counts as a fever

A fever is a rectal temperature of 100.4°F (38°C) or higher. For babies under 3 months, a rectal reading is the most accurate and the one doctors will ask for.

When a fever is an emergency

Age changes everything here. Call your doctor or seek care right away if:

• Under 3 months with any fever of 100.4°F (38°C) or higher — this is always urgent, even if your baby seems fine.
• 3–6 months with a temperature of 102°F (38.9°C) or higher.
• Any age with a fever plus: trouble breathing, a stiff neck, a rash that doesn't fade when pressed, a seizure, unusual sleepiness, or no wet diapers for 8+ hours.

When in doubt with a young baby, call. No one will mind.

What to do at home (older babies, acting okay)

For babies over 6 months who are otherwise comfortable:

• Keep them hydrated — offer breast milk, formula, or fluids more often.
• Dress light — one light layer, not bundled up.
• Medication if needed — acetaminophen (over 2 months) or ibuprofen (over 6 months), dosed by weight, not age. Confirm the dose with your doctor or pharmacist.
• Comfort over numbers — treat how your baby feels, not the thermometer reading.

What not to do

• Don't use cold baths, alcohol rubs, or ice — they cause shivering and can raise temperature.
• Don't double up medications without medical advice.
• Don't wake a peacefully sleeping baby just to give medicine.

Trust the whole picture

A baby who is feverish but drinking, making wet diapers, and still has moments of alertness is usually okay to watch at home. A baby who is limp, inconsolable, or refusing all fluids needs to be seen — regardless of the exact number.

This is the kind of moment Baby Signal is built for: instead of spiraling, you describe what you're seeing — "101.5°F, four months old, still feeding" — and get a clear read on whether to watch, comfort, or call.

When your baby is unwell it is hard to know what is routine and what needs a call. Baby Signal helps you track symptoms over time so changes do not slip past you. Get Baby Signal.

The takeaway

Under 3 months, any fever means call. Older babies who are drinking and have calm moments can often be comforted at home. Always treat the baby, not the number — and never feel silly for checking in with your doctor.