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.
Older man in bed looking at thermometer
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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. 

Influenza(external link) Health New Zealand | Te Whatu Ora


Do you know the difference between a cold and influenza?(external link) Whanganui, Health New Zealand | Te Whatu Ora, 2013
After your immunisation(external link) HealthEd, NZ, 2017
Thermometers - how to use them(external link) KidsHealth, NZ, 2015


  1. Fever and night sweats(external link) Patient Info, UK, 2015
  2. Cold season – managing without antibiotics(external link) BPAC, NZ, 2018
  3. Danger signs during pregnancy(external link) Health New Zealand | Te Whatu Ora
  4. Fever in adults(external link) NHS Inform, UK, 2020

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:

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