What fever temperature is dangerous?

Normal body temperature is around 37oC, although it does vary between and within individuals. For example, body temperature falls during sleep, dropping to its lowest at around 4am and then peaking during the late afternoon.1 It can vary up to half a degree celcius.1

A fever or increase in body temperature significantly above normal is usually caused by a viral or bacterial infection. The rise in temperature is an immune system defence mechanism, designed to kill off the infection because it’s harder for the invading organism to survive at a higher temperature.2

Scientists suggest that a body temperature of 39oC is classified as a mild fever and may help the immune system fight the infection (because of the reason above). Anything above 39.4oC can be dangerous, so seek medical advice.

In children between the ages of 6 months and 6 years, a fever can also trigger convulsions.3 Convulsions (called febrile convulsions) are reasonably rare, only affecting about 3% of children.4 For peace of mind, please consult your doctor if it happens.

A fever if 42.4oC or higher, particularly in the elderly, can cause permanent brain damage.3

A fever is also considered dangerous in the following cases:4

  • If a baby under 3 months has a fever – seek medical assistance immediately
  • Also seek medical attention in both children and adults if the person with the fever:
    • Has trouble breathing
    • Is drowsy
    • Is dehydrated (refusing to drink and not urinating much)
    • Has a stiff neck
    • Is sensitive to light
    • Is vomiting or suffering diarrhoea
    • Is looking pale, weak, or lethargic
  • If the fever persists after three days
  • If the person is shivering or shaking uncontrollably
  • Feels hot but not sweating
  • Seems to be getting sicker
  • They have recently travelled overseas

Digital thermometers are a simple and affordable way to quickly measure your own or a child’s temperature. While a mild fever may help fight infections, ongoing monitoring of body temperature is critical as an alert to seek medical attention when required.

Check out the range of Welcare and Omron thermometers here.


  1. https://www.ncbi.nlm.nih.gov/books/NBK331/
  2. https://medlineplus.gov/fever.html
  3. https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/fever
  4. https://www.health.qld.gov.au/news-events/news/what-is-a-fever-high-temperature-should-you-take-your-child-to-the-doctor



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