Fever: Symptoms, treatments, types, and causes

Fever is when a human’s body temperature goes above the normal range of 36–37° Centigrade (98–100° Fahrenheit). It is a common medical sign.

Other terms for a fever include pyrexia and controlled hyperthermia.

As the body temperature goes up, the person may feel cold until it levels off and stops rising.

Woman with a fever
Fevers are common but can be unpleasant.

People’s normal body temperatures may vary and are affected by factors such as eating, exercise, sleeping, and what time of the day it is. Our body temperature is usually at its highest at around 6 p.m. and at its lowest at about 3 a.m.

A high body temperature, or fever, is one of the ways our immune system attempts to combat an infection. Usually, the rise in body temperature helps the individual resolve an infection. However, sometimes it may rise too high, in which case, the fever can be serious and lead to complications.

Doctors say that as long as the fever is mild, there is no need to bring it down – if the fever is not severe, it is probably helping to neutralize the bacterium or virus that is causing the infection. Medications to bring down a fever are called antipyretics. If the fever is causing undue discomfort, an antipyretic may be recommended.

When a fever reaches or exceeds 38° Centigrade (100.4° Fahrenheit), it is no longer mild and should be checked every couple of hours.

These temperatures refer to oral measurement, when the thermometer is put in the mouth. For normal armpit temperatures, the temperature measures lower than it actually is and the numbers are reduced by about 0.2–0.3° Centigrade.


When somebody has a fever, signs and symptoms are linked to what is known as sickness behavior, and may include:

A woman holding a thermometer showing fever temperature.
Temperature can be measured in the mouth, rectum (anus), under the arm, or inside the ear.

feeling cold when nobody else does


lack of appetite

dehydration — preventable if the person drinks plenty of fluids


hyperalgesia, or increased sensitivity to pain


problems concentrating



If the fever is high, there may also be extreme irritability, confusion, delirium, and seizures.


Non-steroidal anti-inflammatory drugs (NSAIDs) such as aspirin or ibuprofen can help bring a fever down. These are available to purchase over-the-counter or online. However, a mild fever may be helping combat the bacterium or virus that is causing the infection. It may not be ideal to bring it down.

If the fever has been caused by a bacterial infection, the doctor may prescribe an antibiotic.

If a fever has been caused by a cold, which is caused by a viral infection, NSAIDs may be used to relieve uncomfortable symptoms. Antibiotics have no effect against viruses and will not be prescribed by your doctor for a viral infection.

Fluid intake: Anyone with a fever should consume plenty of fluids to prevent dehydration. Dehydration will complicate any illness.

Heat stroke: NSAIDs will not be effective if the person’s fever was caused by hot weather or sustained strenuous exercise. The patient needs to be cooled. If they are confused or unconscious, they should be treated by a doctor straight away.

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Fever can be caused by a number of factors:

an infection, such as strep throat, flu, chickenpox, or pneumonia

rheumatoid arthritis

some medications

overexposure of skin to sunlight, or sunburn

heat stroke, resulting either by exposure to high temperatures or prolonged strenuous exercise


silicosis, a type of lung disease caused by long-term exposure to silica dust

amphetamine abuse

alcohol withdrawal

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