Fever in Adults

Your normal body temperature is approximately 37°C. A fever is usually when your body temperature is 37.8°C or higher. You may feel warm, cold or shivery.

You can find out if you have a fever by using a thermometer to take your temperature

What causes a fever?

A fever is your body’s natural response to many common illnesses such as:

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

When to get help

Contact your GP practice if:

  • you have severe thirst or are peeing less
  • you are passing urine that is darker than normal
  • you are light-headed or weak
  • you have new, severe muscle cramps
  • your symptoms have worsened or you notice new symptoms
  • you’ve had a fever after recent foreign travel

If your GP practice is closed, phone 111.

Contact your GP practice immediately if:

You have a fever and you:

  • are on treatment for immune deficiency
  • are on immune-suppressant drugs, such as regular steroids, methotrexate, azathioprine or cyclophosphamide
  • are taking medication where you have been warned about a risk of a reduced immune system
  • are on, or recently completed, treatment for cancer, leukaemia or lymphoma
  • are a transplant recipient
  • are HIV positive
  • have chronic lung disease
  • have asthma which has been treated with medication in the last 3 years
  • have heart disease (excluding blood pressure which is currently well controlled)
  • have diabetes or another metabolic disease
  • have chronic gastrointestinal or liver disease
  • have chronic renal (kidney) disease
  • have cystic fibrosis
  • have neurological conditions such as cerebral palsy, stroke, multiple sclerosis or muscular dystrophy
  • have sickle cell disease

Treating a fever

Most fevers will improve on their own in a few days. However, there are a number of things you can do to help the uncomfortable feelings associated with a fever.


  • wear loose comfortable clothing
  • make sure the room you are in isn’t too warm
  • drink more fluids (for example water) so you don’t get dehydrated – you should be peeing approximately every 6 hours (a pale yellow urine means you’re unlikely to be dehydrated)
  • avoid alcohol as this can make dehydration worse
  • take a medicine that reduces fever such as paracetamol (unless you’re allergic or have been told by a healthcare professional that you can’t take it)


  • do not over dress
  • do not attempt to make yourself feel cold