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A fever is a high body temperature. It's one way your body fights being sick. A fever shows that the body is responding to infection or other illnesses, both minor and severe.
A fever is a symptom, not an illness by itself. A fever can be a sign that you are ill, but most fevers are not caused by a serious problem.
You may have a fever with a minor illness, such as a cold. But sometimes a very serious infection may cause little or no fever. It is important to look at other symptoms, other conditions you have, and how you feel in general. In children, notice how they act and see what symptoms they complain of.
A normal body temperature is about 37ºC. Some people have a normal temperature that is a little higher or a little lower than this.
Your temperature may be a little lower in the morning than it is later in the day. It may go up during hot weather or when you exercise, wear heavy clothes, or take a hot bath.
Your temperature may also be different depending on how you take it. A temperature taken in the mouth (oral) or under the arm may be a little lower than your core temperature (rectal).
A core temperature of 38°C or above is considered a fever.
A fever may be caused by:
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.
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Current as of: November 14, 2022
Author: Healthwise Staff
Medical Review:Adam Husney MD - Family Medicine & Kathleen Romito MD - Family Medicine & David Messenger MD - Emergency Medicine, Critical Care Medicine
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