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.
Fever in adults self-help guide
Complete our self-help guide to check your symptoms and find out what to do next.
Fever in adults
Before using this guide
If you’re asking on behalf of someone else, please make sure the person is:
- conscious and alert
- responding normally to you
If not, phone 999 and ask for an ambulance.
Coronavirus (COVID-19)
If you’re worried about coronavirus, read our coronavirus guidance.Start guide
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 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
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.
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.
Do
- 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)
Don’t
- do not over dress
- do not attempt to make yourself feel cold
Fever in children
Fever affects people of all ages, however it often affects babies and younger children in response to minor illnesses such as:
- coughs
- colds
Find out more about fever in children.
