Also known as a high temperature

Key points about fever

  • A fever is when your core temperature is raised above 38°C. It often accompanies an infection, such as a cold or flu.
  • Normal body temperature for children and adults is around 37ºC (degrees Celsius). You have a fever if your temperature is between 38ºC and 38.9ºC and a high fever when your temperature is 39ºC or over.
  • Usually, you will feel unwell and hot, and you may sweat. Sometimes you will feel very cold and shivery even when your temperature is high.
  • You can use a thermometer to find out how high your temperature is. Read more about thermometers and how to use them.
  • This page provides general information about fever. If you have a child with a fever, see fever in children.
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A fever usually lasts 3–5 days and most people recover from a mild fever by managing their symptoms at home. However, there are times when you should see a doctor urgently for fever

  • Drink plenty of fluids, especially water or rehydration fluid (little and often is best). You sweat more when you have a fever. Drink enough so your urine (pee) is light yellow and clear.
  • Rest while you recover.
  • Open a window for ventilation but avoid draughts.
  • Wear lightweight comfortable clothing and use lighter bedding. Don't use hot water bottles or electric blankets.
  • Use a cool cloth to wash your face, hands and neck.
  • Change bed linen and clothing regularly, especially if they are wet from sweat. 

Although most fevers will settle down in a few days and are not worrying, you sometimes need to seek medical advice.

Contact a healthcare provider or call Healthline 0800 611 116 for advice: 

If you have a fever and the following symptoms:

  • a high fever (39ºC or over)
  • you are passing urine that is darker than normal
  • you are still feverish after 3 days or seem to be getting sicker
  • you are shivering or shaking uncontrollably, or have chattering teeth, and it doesn’t stop within an hour or so
  • you have a severe headache that doesn’t get better after taking pain medicines
  • are having trouble breathing
  • are getting confused or are unusually drowsy
  • have recently travelled overseas.

If you have a fever and you are:

  • being treated for immune deficiency
  • on immune-suppressant drugs, such as regular steroids, methotrexate, azathioprine or cyclophosphamide
  • taking medication where you have been warned about a risk of a reduced immune system
  • having, or have recently completed, treatment for cancer, leukaemia or lymphoma
  • a transplant recipient
  • HIV positive.

If you’re pregnant and have a fever, check with your midwife, doctor or nurse before you take any medicines. If your fever lasts for longer than a day, talk to your lead maternity carer (LMC).

Call 111 and ask for an ambulance or go to the nearest hospital

If you have a fever and any of the following symptoms: 

  • Hallucinations.
  • Vomiting.
  • A stiff neck (unable to put your chin on your chest or have pain when moving your neck forward).
  • A skin rash.
  • A rapid heart rate.
  • A seizure (fit), or experience signs of a seizure about to happen, such as regular twitching or jerking.

A viral infection is the most common cause of a fever. A bacterial infection is less common but is more serious. Your body's natural reaction to infection is to raise your body temperature. This helps kill the infection. Vaccination sometimes causes a mild fever too.

Fever is your body’s way of fighting infection. Medicine is not needed for mild fever, but you can use paracetamol if you also have a headache or muscle pain. 

flu handout 204x300

The difference between influenza and a cold

Ministry of Health NZ, 2013

after your immunisation moh nz

After your immunisation

HealthEd, NZ, 2017

thermometres and how to use them kidshealth nz 001

Thermometers - how to use them

KidsHealth, NZ, 2015

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Credits: Healthify editorial team. Healthify is brought to you by Health Navigator Charitable Trust.

Reviewed by: Dr Sharon Leitch, GP and Senior Lecturer, University of Otago

Last reviewed:

Page last updated: