Fever in babies: temperatures by age and when to get help

A temperature of 38°C (100.4°F) or more is a fever. If your baby is under 3 months, any reading of 38°C or more needs emergency assessment straight away, even if they seem fine: call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) or go to the nearest emergency department. For older babies, a fever is usually the body fighting an everyday infection, and how your baby looks, feeds and responds matters more than the exact number. At any age, some signs mean calling your local emergency number (000 in Australia, 999 in the UK, 911 in the US) no matter what the thermometer says.

This guide covers taking a temperature, the thresholds by age, comfort care, medicines and febrile seizures. The urgency tiers match our when to call the doctor guide.

What temperature counts as a fever in a baby?

The Royal Children's Hospital Melbourne (RCH), the NHS and the American Academy of Pediatrics (AAP) all use 38°C (100.4°F) or more as a fever.

The World Health Organization uses a slightly different cut-off in its guidance for health workers. Its IMCI fever module treats an armpit temperature of 37.5°C or more as a fever in children aged 2 months to 5 years. It notes rectal readings run about 0.5°C higher. Cocoon uses the 38°C threshold that Australian, UK and US parent guidance uses.

Feeling your baby's forehead is a quick check, but the RCH suggests using a thermometer when you need to be sure. NICE also tells clinicians to take a parent's sense that their child has a fever seriously.

How do I take my baby's temperature?

The best method depends on your baby's age and on where you live:

NICE advises against routinely using oral or rectal readings in children under 5, so UK and Australian parents usually measure under the arm. The RCH says forehead strips and infrared forehead thermometers can be unreliable for children. The AAP says not to use mercury thermometers at all.

Taking an underarm temperature

1. Use a digital thermometer and follow its leaflet.
2. Place the tip in the top of the armpit, against skin, not clothing.
3. Hold your baby's arm gently against their side until the thermometer beeps or the leaflet's time is up.
4. If your baby has just had a bath or been wrapped up, the NHS suggests waiting a few minutes before checking.
5. Write down the reading, the time and the method.

What should I do if my baby under 3 months has a fever?

Treat it as an emergency, even if your baby seems well. The NHS urgent-help guide lists 38°C or more under 3 months among reasons to call an ambulance or go to A&E. NICE classes it as a high-risk sign, and the RCH advises taking a baby under one month with a fever to hospital. The AAP also says to call the doctor right away.

Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) or go straight to the nearest emergency department. Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) rather than driving if your baby also has trouble breathing, a colour change, a seizure or is hard to wake.

NICE notes that some vaccinations can cause a fever in babies under 3 months. Ask at the vaccination appointment what to expect and what to do. If you haven't been given specific advice for your baby, follow the under-3-months rule above. Our vaccinations guide covers what to expect after vaccines.

When does a fever need a doctor at 3 months and older?

From 3 months, the decision rests more on how your baby is than on the reading. Use this table alongside the red flags in the next section:

For 3- to 6-month-olds, the NHS urgent-help guide lists 39°C or more among reasons to call an ambulance or go to A&E, so we put it in the your local emergency number (000 in Australia, 999 in the UK, 911 in the US) tier. The NHS fever page lists it for an urgent call to its advice line instead, NICE treats it as at least intermediate risk, and the urgent-help guide's longer list leaves out babies who had a vaccine in the past 2 days. Our vaccinations guide explains why we still use the stricter tier after vaccines.

How long a fever lasts matters too. NICE and the NHS say a fever lasting 5 days or more should be checked. The AAP sets a lower bar: call if a fever lasts more than 24 hours in a child under 2.

The RCH says there's no need to treat a fever if your child seems otherwise well and comfortable. NICE also notes that in babies over 6 months, the height of the temperature alone doesn't show how serious an illness is.

Which fever symptoms mean call your local emergency number (000 in Australia, 999 in the UK, 911 in the US)?

Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US) at any age if your baby has a fever and:

• Has a seizure (fit). See the febrile seizure section below.
• Has a stiff neck or a bulging soft spot (fontanelle).
• Has a rash that doesn't fade when you press a glass against it. On brown or black skin, check the palms and soles.
• Is struggling to breathe, grunting, breathing very fast, or pausing between breaths.
• Has blue, grey, very pale or blotchy skin, lips or tongue, or unusually cold hands and feet.
• Is floppy, drowsy and hard to wake, or not responding as usual.
• Has a weak, high-pitched or continuous cry.
• Has had no wet nappy for 12 hours.

These come from the NHS fever and urgent-help guides and the NICE traffic-light table. NICE's table also lists signs for the next tier.

Get medical help today if your baby is feeding much less than usual, has fewer wet nappies, a dry mouth or no tears, or isn't their usual self. For a baby under 6 months, any sign of dehydration needs a doctor that day. See dehydration signs.

How can I keep my baby comfortable with a fever?

Comfort and fluids matter more than getting the number down.

1. Offer plenty of fluids. The RCH suggests extra breastfeeds or more frequent bottle feeds for babies under 6 months. NICE says breast milk is the best fluid for a breastfed baby.
2. Dress them in light clothing. Don't wrap them up to "sweat it out", and don't strip them off. NICE says children with a fever shouldn't be underdressed or over-wrapped.
3. Skip cold baths and sponging. The RCH says cold water can make children shiver more, the NHS advises against sponging, and NICE says tepid sponging isn't recommended.
4. Keep checking, including overnight. NICE advises checking on a feverish child during the night and watching for dehydration and non-fading rashes.
5. Keep them home. NICE advises keeping children away from childcare while they have a fever.

Should I give my baby paracetamol or ibuprofen?

Fever medicine can help a baby who is miserable or uncomfortable, but it doesn't treat the infection. NICE says not to use it just to lower the temperature. Use the dose on the product label for your baby's age and weight, or ask your pharmacist, GP or child-health nurse.

The NHS fever page sets age limits:

• Don't give paracetamol to a baby under 2 months.
• Don't give ibuprofen to a baby under 3 months or under 5 kg.
• Don't give ibuprofen to a child with chickenpox or who is dehydrated.
• Don't give aspirin to children.

For a baby under 3 months, get your baby seen rather than treating at home. A temperature that comes down after medicine doesn't rule out serious illness. NICE tells clinicians not to rely on that.

Sources differ on using both medicines. The NHS says not to alternate them unless a health professional advises it. NICE says not to give both at the same time, and to consider alternating only if distress persists or comes back before the next dose is due. The RCH says it's safe to give both, following each pack's instructions. Ask your pharmacist which approach suits your baby, and keep a written note of every dose and time.

What is a febrile seizure and what should I do?

A febrile seizure (febrile convulsion) is a fit caused by a sudden rise in body temperature. The RCH febrile seizures fact sheet says they're most common between 6 months and 6 years. Children usually lose consciousness and may stiffen or go floppy, jerk or twitch, and go red or blue in the face.

If it happens:

1. Place your child on their side on a soft, low surface.
2. Don't hold them down, and don't put anything in their mouth, including your fingers.
3. Time the seizure if you can.
4. Call your local emergency number (000 in Australia, 999 in the UK, 911 in the US). The NHS urgent-help guide lists any seizure as a reason to call an ambulance. The RCH says an ambulance is essential if it's their first seizure, if it lasts 5 minutes, or if they don't wake up after it stops, and to see a doctor after any other febrile seizure.

The RCH says febrile seizures rarely cause long-term health effects. Paracetamol and ibuprofen won't prevent them, and NICE agrees that fever medicine shouldn't be used for that purpose.

What is worth writing down during a fever?

Note each temperature with the time and method, every dose of medicine and when it was given, feeds and wet nappies, and any new symptoms. This helps you avoid doubling up on medicine and gives a doctor a clear picture. If your baby seems very unwell, get help first and note things down later.