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By Bjarne Lühr Hansen PhD, MD and Philipp Skafte-Holm MD, Mentor Institute

Your general condition is more important than how high your temperature is. You should dress lightly and drink plenty with fluid. A fluctuating temperature can be sign of serious illness. If you are drowsy or have trouble breathing, you must call the doctor immediately.

Fever is a sign of illness that, however, does not say anything about how serious the illness is. If you have a high fever but want to read, listen to the radio or watch TV, you are only rarely seriously ill. On the other hand you can be seriously ill if you prefer lying in bed all day without doing anything, even though you inly have a light fever. The general condition is said to be good, when you, as described above, feel somewhat okay and want to be entertained. The general condition is important, when deciding how ill someone is.

The temperature should be measured in the rectum after 10 minutes rest. Normally, the temperature is lower than 37,0ºC in the morning and lower than 37,5ºC in the evening. If the temperature is higher than 38.0ºC, you have a fever. When you have a fever, your metabolism increases, you lose fluid and the pulse rises.

As a rule of thumb, your body will – for every 1 degree your temperature is over 37,0ºC – lose ½ litre fluid during 24 hours. If your temperature for example is 39,0ºC for 24 hours, this means that you lose 1 litre extra fluid. It can be dangerous to lose too much fluid. Therefore, it is important to drink plenty when you have a fever.

Fever is sign of infection somewhere in the body. Far most cases of fever are of the duration of a few days, most often, the cause is virus and, more rarely, bacteria.

There are special types of fever that you must pay attention to:
If your temperature fluctuates a lot within 24 hours – for example 40ºC in the morning, 37ºC at midday and 40ºC in the afternoon.

If you fever lasts more than 5 days.

If you have had fever for some days, are well and free of fever and then have a fever again within a few days.

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Depends on the cause of the fever.

When can I go to work?
When the temperature is normal.


It is a good idea to take antipyretic medication (paracetamol or aspirin) for example before going to bed since it gives you a calmer sleep.

What can you do?

You should dress lightly and stay in a cool room to make the temperature drop. You should drink plenty since you lose fluid. You do not need to stay in bed, if you prefer staying up.

Contact the doctor tomorrow

When you have a fever and cannot drink enough. If your fever lasts longer than 5 days. If you have had a fever for some days and have become well can free of fever and then have a fever again within a few days.

Contact the doctor immediately

If you are drowsy and want to sleep the whole time. If you have a fever and have trouble breathing. If your temperature is higher than 40,0ºC. If your temperature fluctuates a lot.