The thermometer reads 37.5, and you're already googling the worst-case scenario. In reality, the number alone means little. Look at how you feel and what else is going on alongside the temperature.
What temperature is considered normal
Normal temperature varies from person to person. It changes throughout the day. So there is no single "correct" number.
A fever is considered a temperature of 38 °C and above, including when measured under the arm.
Also go by how you feel. If you feel hot, cold, or are shivering, your temperature may be elevated even at a reading below 38 °C.
Your skin can give clues too. Your chest or back feels hotter to the touch than usual, and the skin itself is warm and reddened. On darker skin, redness is harder to notice.
Why the body develops a fever
Fever is the body's response to an irritant, most often an infection. Thermoregulation is reset, and body temperature rises.
The point is simple: immune cells work more actively. It is easier for them to neutralize the pathogen when the body is warmer.
Elevated temperature hinders the reproduction of viruses, bacteria, and other microorganisms. It is part of the work of the body's defenses.
At the cellular level, this means increased phagocytosis and greater synthesis of interferons. Lymphocyte activation and stimulation of antibody production are added to this.
Why temperature rises
Most often the cause is an infection. Fever often accompanies a cold or flu. Usually it resolves on its own.
There can also be non-infectious causes. These include inflammatory processes and connective tissue diseases. Sometimes fever becomes the first manifestation of malignant tumors or lymphoproliferative diseases.
Fever occurs even when the ambient temperature is normal or low. Because it is a consequence of disrupted thermoregulation, not overheating.
That is precisely why a prolonged unexplained fever is a complex diagnostic challenge. It is solved together with a doctor, not on your own.
The three stages of fever
First, the temperature rises. Heat production exceeds heat loss, and the skin's blood vessels constrict. The person turns pale, "goosebumps" appear, along with muscle trembling and chills. There is often a headache, muscle aches, weakness, and thirst.
Next, the temperature stays at a high level. Heat production equalizes with heat loss. The person feels hot, the face reddens, thirst appears, and appetite is lost.
Then the temperature drops. This can happen gradually, over 2–3 days, and the condition improves. Or abruptly: the temperature falls from 40–41 °C to 37–36 °C. Such a drop is dangerous because of collapse — the skin turns pale, the limbs grow cold, and sweat becomes cold and clammy.
The pulse quickens during fever. According to Liebermeister's rule — by 8–10 beats per minute for each degree above 37 °C in an adult.
Daily fluctuations also matter. With a constant fever, the difference between morning and evening temperature does not exceed 1 °C. With a remittent fever, it exceeds 1 °C.
How to measure correctly
A thermometer is not essential, but it makes things easier. The main thing is to use it correctly.
- Digital thermometer: wash the tip with cold water and soap and rinse it.
- Turn on the device and place the tip under the tongue, closer to the back of the mouth.
- Close your lips tightly and wait for the beep.
- In the armpit, keep your arm pressed against your body until the beep.
- Glass thermometers are dangerous, and forehead strips are inaccurate.
Follow the instructions for your specific device. The procedure may differ between models.
When to see a doctor and when to call an ambulance
Most elevated temperatures resolve on their own. But sometimes medical help is needed.
See a doctor if the temperature does not come down at home or you get worse. This is a reason for an urgent appointment.
Sometimes an elevated temperature can be a sign of a serious condition if it is very high or does not come down.
Call an ambulance (103 or 112) if, along with the temperature, there are seizures, loss of consciousness, difficulty breathing, or signs of sepsis — confusion or slurred speech, mottled, bluish, or very pale skin.
This material is for reference and does not replace a doctor's consultation.
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This content is for reference and does not replace a doctor's consultation. Medical disclaimer