A fever in a baby or young child is one of the most common reasons parents call their GP or 111 - and one of the most stressful. Here's what NHS guidance actually says, without the noise.
What counts as a fever?
A temperature of 38°C or above is considered a fever in children. Normal body temperature is around 36.4°C, though it varies slightly throughout the day. The most reliable reading for babies under 5 is with a digital thermometer under the armpit.
When to act - by age
Under 3 months
A fever of 38°C or above in a baby under 3 months old always needs medical assessment. Contact your GP or call 111 immediately, even if your baby seems well otherwise. Young babies can become seriously unwell quickly.
3 to 6 months
Contact your GP or call 111 if the temperature reaches 39°C or above, or if your baby has a temperature of 38°C and seems unwell - less responsive than usual, not feeding, or unusually irritable.
Over 6 months
Most fevers in babies over 6 months can be managed at home. Focus on how your child is behaving, not just the number on the thermometer. A child who is alert, drinking, and playing with a temperature of 39°C is less concerning than a child who is listless and refusing fluids at 38.5°C.
Managing a fever at home
Keep your child hydrated - offer breast milk, formula, or water regularly in small amounts. Dress them in light clothing and keep the room at a comfortable temperature - don't over-bundle them, but don't strip them down either.
You can offer paracetamol (from 2 months if over 4kg) or ibuprofen (from 3 months if over 5kg) if your child is uncomfortable. Follow the dosage on the packaging for their age and weight. Don't give both at the same time, but you can alternate if one alone isn't helping.
Do not use cold baths or sponging - NHS guidance no longer recommends this as it can cause shivering, which actually raises the body temperature.
Fever after vaccinations
A mild fever within 48 hours of a vaccination is very common and is a sign that the immune system is responding. It typically resolves within a day or two. You can give infant paracetamol if your baby is uncomfortable.