What is a Fever (or High Temperature) in Children?

Sick day TLCAs a general rule, a temperature of over 37.5C (99.5F) is classified as a fever.

You can use a thermometer to find out if your child has a fever. For more information, see How do I take someone’s temperature?

Causes of fever

Most fevers are caused by an infection or another illness.

Fever helps your body fight infections by stimulating the body’s natural defences. By increasing the body’s temperature, a fever makes it harder for the bacteria and viruses that cause infections to survive.

There are many conditions that can cause fever. Most fevers are cause by a viral illness that will get better by itself without any specific treatment. Occasionally a fever may be caused by more serious infection, such as pneumonia or meningitis.

Don’t try to reduce your child’s fever by over or under dressing them, or sponging them with water. You can use paracetamol or ibuprofen to treat any distress or discomfort caused by the fever and being unwell. Read more information about treating a high temperature and giving your child paracetamol and ibuprofen.

Getting help

If you’re worried about your child, trust your instincts. Speak to your doctor or your child’s pediatrician.

If your doctor’s office is closed, contact their out-of-hours service. You will be informed about how to do this when you ring their phone line. If you’re still concerned, or if your doctor or out-of-hours provider isn’t available, take your child to the nearest hospital’s accident and emergency department (A&E or E.R).

Symptoms of serious illness

Symptoms that may be a sign of a more serious illness include:

  • being unusually sleepy
  • poor feeding
  • having a non-blanching rash (a rash that doesn’t fade when a glass is pressed firmly against the skin; this is known as the glass test)
  • a continuous or high-pitched cry
  • For more signs of serious illness and advice on when to call an ambulance for your child, see Recognising signs of serious illness.

Febrile seizures

Febrile seizures (or fits) sometimes happen in children who have a high temperature, but are a rare occurrence. Read more about febrile seizures.

Read the answers to more questions about children’s health.

Further information:

NHS Choices logo

From www.nhs.uk

About the Author

NHS Choices (www.nhs.uk) is the UK’s biggest health website. It provides a comprehensive health information service to help put you in control of your healthcare.


3 Responses to “What is a Fever (or High Temperature) in Children?”

  1. Doc says:

    A fever is temperature greater than 38°C, or 100.4°F. A temperature of 99.5 is still within normal range and can be a part of normal daily variation. Telling parents a fever occurs at a temperature less than 38°C will just increase the amount of antipyretics given to young children and increases the risk for overdose and overuse of these medications.

    • Stefanie Zucker Stefanie Zucker says:

      Hi Doc,

      Thanks for stopping by! And great comment! As far as exactly what temperature is classified as a fever, interestingly enough, both the NHS (UK’s National Health Service…and the author of this article) and NIH (US National Institute of Health) vary their responses – in some cases by age of the child, and in others by the way the temperature is taken.

      According to the NHS “A normal temperature is around 37ºC (98.6ºF), although it depends on: the person, their age, what they’ve been doing, the time of day and which part of the body you take the temperature from. A fever (high temperature) is a temperature of 38ºC (100.4ºF) or over. However, in children under five, a fever is a temperature of more than 37.5ºC (99.5ºF).”

      According to the NIH – “A child has a fever when the temperature is at or above one of these levels: 100.4 °F (38 °C) measured in the bottom (rectally), 99.5 °F(37.5 °C) measured in the mouth (orally) and 99 °F (37.2 °C) measured under the arm (axillary)

      I think some key points they both make is what symptoms to be concerned about (i.e. are potentially serious) as well as reminding parents – if you’re concerned call your doctor or pediatrician.

      Once again, thanks Doc for the terrific comment…we appreciate your giving us the opportunity to elaborate on this. Have a great weekend!


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