Pregnancy information

How to take a baby's temperature

A normal temperature in children is about 36.4C (97.5F) but this does vary slightly. A fever is usually considered to be a temperature of 38C (100.4F) or above.

Your baby may have a fever if they:

  • feel hotter than usual to the touch – on their forehead, back or stomach
  • feel sweaty or clammy
  • have flushed cheeks

If you think your baby has a fever, it's best to check their temperature with a thermometer. This will help you work out whether you need to get medical advice.

How do I take my child’s temperature?

Ideally, you need a digital thermometer to get a fast, accurate reading. You can buy these online or from pharmacies and most large supermarkets.

To take your child's temperature:

  • hold them comfortably on your knee and put the thermometer in their armpit - always use the thermometer in the armpit with children under five
  • gently but firmly, hold their arm against their body to keep the thermometer in place for however long it says in the maufacturer's instructions - usually about 15 seconds; some digital thermometers beep when they're ready
  • the display on the thermometer will then show your child's temperature

How can I make sure the reading is accurate?

If you use a digital thermometer in your child's armpit and follow the manufacturer's instructions carefully, you should get an accurate reading.

There are a few things that can slightly alter the reading – for example, if your child has been:

  • wrapped up tightly in a blanket
  • in a very warm room
  • very active
  • cuddling a hot water bottle
  • wearing a lot of clothes
  • having a bath

If this is the case, allow them to cool down for a few minutes, but do not let them get cold or shivery, then take their temperature again to see if there's any change.

Other types of thermometer

You can buy other types of thermometer, but they may not be as accurate as a digital thermometer for taking a baby or small child’s temperature.

  • Ear (tympanic) thermometers - these allow you to take a temperature reading from the ear. These thermometers are quick but expensive; they can give misleading readings if they’re not correctly placed in the ear, which is more likely to happen with babies because their ear holes are so small
  • Strip-type thermometers - these are held on to the child’s forehead, and are not an accurate way of taking a temperature. They show the temperature of the skin, rather than the body.

You should never use an old-fashioned glass thermometer containing mercury. These can break, releasing small splinters of glass and highly poisonous mercury. They're no longer used in hospitals and you can't buy them in shops.

If your child is exposed to mercury, get medical advice immediately.

What causes a fever in children?

Fever is usually a sign that your child's body is trying to fight an infection.

Some babies and young children get a fever after having their vaccinations. This should clear up quite quickly by itself. If you’re concerned speak to your health visitor or GP.

What should I do if my baby has a fever?

You can usually look after your baby or child at home when they have a fever. Make sure they get plenty of drinks to avoid dehydration. If you're breastfeeding, offer your baby plenty of feeds.

Always contact your GP or 111 if:

  • your child has other signs of illness, such as a rash, as well as a high temperature
  • your baby’s temperature is 38C (101F) or higher if they’re under three months
  • your baby’s temperature is 39C (102F) or higher if they’re three to six months

If you need to speak to someone outside normal surgery hours, you can call NHS 111 Wales.

Find out more in Treating a high temperature in children.

Last Updated: 05/07/2023 09:20:36
The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website