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Baby thermometer

Infections can cause a high temperature or fever in children. We discuss the signs and symptoms of fever, the causes and when to seek medical advice.

If your baby or child has a high temperature or fever it can be worrying.

Remember that you know your little one best. If you feel something isn’t right or are concerned, especially with a young baby, you could contact your GP or call NHS 111.

What is a fever?

  • A temperature of 38°C (100.4°F) or above is generally classified as a fever in children.

  • This can vary from child to child so trust your instincts. You know your little one better than anyone else. If you are worried contact your GP, health visitor, out of hours service or NHS 111.

  • Fever is very common in children and over 60% of parents with children aged six months to five years say their child has had one. (NHS, 2020a)

How do I know if my child has a fever?

Signs your little one has a fever may include:

  • flushed cheeks.

  • feeling sweaty or clammy.

  • being hotter than usual to the touch on their forehead, back or tummy. (NHS, 2020a)

If you think your child has a fever use a digital thermometer to check their temperature.

  • In children under five years old, it’s recommended to take their temperature under their armpit rather than the ear or mouth. This gives a more accurate reading.

  • Hold your child on your lap and place the thermometer under their armpit. Holding their arm in to the side of the body until the reading is ready – usually around 15 seconds.

  • Forehead thermometers are unreliable and so not recommended.(NICE, 2019)

An underarm temperature of 36.4°C (97.5°F) is considered normal in babies and children and any temperature over 38°C (100.4°F) is classified as a fever (NHS, 2020a).

What causes a fever in children and babies?

Most fevers are caused by infections or other illnesses. Your baby’s high body temperature is a natural response. It makes it more difficult for the bacteria and viruses that cause infections to survive (NHS, 2020a).

Common conditions that can cause fevers include:

  • Respiratory tract infections (RTIs)

  • Flu

  • Ear infections

  • Roseola – a virus that causes a fever and a rash

  • Tonsillitis

  • Kidney or urinary tract infections (UTIs)

  • Common childhood illnesses like chickenpox and whooping cough.

"Your child's temperature can also be raised after vaccinations, or if they overheat because of too much bedding or clothing (NHS, 2020b)."

Sometimes a high temperature in babies and children is associated with more serious illnesses like:

  • Meningitis – infection of the protective membranes that surround the brain and spinal cord.

  • Septicaemia – infection of the blood.

  • Pneumonia – inflammation of the lung tissue, usually caused by an infection. 

  • Group A Strep 

It's important to remember that serious causes of fever are relatively rare. But if you are worried about your child, seek medical advice immediately.

What should I do if my child has a fever?

Mild fevers are usually nothing to worry about and can often be treated at home.

The NHS recommends you get an urgent appointment with your GP or call NHS 111 if:

  • Your baby is under three months old and has a temperature of 38°C (101°F) or above.

  • Your baby is three to six months old and has a temperature of 39°C (102°F) or higher.

  • The fever lasts more than five days.

  • Your child has other signs of being unwell, such as persistent vomiting, refusal to feed, floppiness or drowsiness.

  • Your little one is crying constantly and you can't console or distract them. Or the cry doesn't sound like their normal cry.

  • They have a high-pitched or unusual sound when crying.

  • You are worried about your child – trust your instincts if you think they could be seriously ill. (NHS Choices, 2020a)

If your baby or child shows signs of more serious illness, such as blotchy skin or fast breathing, take them to your nearest Accident & Emergency (A&E) department.

Call 999 for an ambulance if your child:

  • Stops breathing.

  • Won't wake up.

  • Is under eight weeks old and you are very worried about them.

  • Has a fit (seizure) for the first time, even if they seem to recover.

  • Has a spotty/purple rash that does not disappear when you press a glass against it – this could be a sign of meningitis or blood poisoning. (NICE, 2019; Meningitis Now, no date)

Febrile seizures, sometimes called febrile convulsions, in babies can be caused by a high temperature (NHS, 2019a). This is because the part of the body that regulates the temperature has not fully developed yet. As a child gets older, their body will get better at regulating their body temperature and the likelihood of febrile seizures will decrease.

If your child is having a febrile seizure, they may become stiff, twitch or lose consciousness. This can be very scary but almost all children make a full recovery (NHS, 2019a).

This page was last reviewed in March 2021

Further information

Our support line offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0300 330 0700.

You might find attending one of our NCT New Baby courses helpful as they give you the opportunity to explore different approaches to important parenting issues with a qualified group leader and other new parents in your area.

Make friends with other parents-to-be and new parents in your local area for support and friendship by seeing what NCT activities are happening nearby.

NCT and the British Red Cross run First Aid courses for parents with babies and children up to 12 years old on life-saving topics, such as CPR, stopping bleeding and what to do if your child is choking. Find your nearest course.

NICE (2019). Fever in under 5s: assessment and initial managements. NICE guidelines [NG143]. Available at: [Accessed March 2021]

NHS (2020a). High temperature (fever) in children. Available at: [Accessed March 2021]

NHS (2020b). Is your baby or toddler seriously ill? Available at: [Accessed March 2021]

Meningitis Now. (no date) Signs and symptoms in babies and toddlers. Available from: [Accessed March 2021].

NHS (2019a). Febrile seizures. Available at: [Accessed March 2021]

NHS (2019b). Reye’s Syndrome. Available at: [Accessed March 2021]

NHS (2018). Can I give my child painkillers? Available at: [Accessed March 2021]


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