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Health

Body temperature

, medical expert
Last reviewed: 06.07.2025
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Usually, body temperature is measured in the armpit, but its measurement in the rectum sometimes has an independent meaning, for example, in case of general cooling of the body, damage to the tissues of the armpit, and also in gynecology for measuring basal body temperature (in order to determine the date of ovulation).

The body temperature in the armpit is considered normal if it is between 36 and 37 °C and fluctuates between several tenths and 1 °C during the day. A noticeable decrease in it is rarely observed (general exhaustion of the body, heart failure, intoxication with some toxic substances, endocrine disorders).

Fever is a protective and adaptive reaction of the body that occurs in response to various irritants and is expressed in the restructuring of thermoregulation to maintain a higher than normal body temperature. A body temperature within 37-38 °C is called subfebrile fever. 38-39 °C is moderate fever, 39-41 °C is high fever, and over 41 °C is hyperpyretic fever.

The temperature measured in the armpit is considered normal if it is fixed within the range of 36 to 37 °C and fluctuates during the day from several tenths to 1 °C. A decrease in temperature is rare in cases of exhaustion, heart failure, and some intoxications.

A body temperature within the range of 37-38 °C is considered subfebrile, 38-39 °C - moderate fever, 39-41 °C - high fever, above 41 °C - hyperpyretic.

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Causes of fever

The causes of fever are varied. The main one is an infectious process of various origins. However, a non-infectious inflammatory process is possible (for example, during myocardial infarction or so-called autoimmune inflammation), sometimes the cause of fever may remain unclear for a long time. Currently, even a syndrome of "fever of unknown origin" is distinguished when the body temperature rises above 38 °C for at least 3 weeks.

The endocrine system has an impact on heat production with an increase in body temperature: for example, with increased thyroid function, subfebrile temperature is often detected.

An increase in temperature may occur with damage to the central nervous system, including those of purely functional origin - "thermoregulatory neurosis", but in this case the temperature is almost never higher than subfebrile.

At present, attention is still being paid to the type of temperature curve that is recorded with the daily morning and evening temperature increase.

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Types of fever

  1. constant (febris continua) - temperature fluctuations do not exceed 1 °C during the day, usually stays within 38-39 °C;
  2. laxative, or remittent (febris remiftens) - daily fluctuations of 1-2 °C (for example, in purulent processes);
  3. intermittent (febris intermittens) - temperature rises to 39-40 °C for a short time (hours) alternate with a decrease to normal and a new increase after 2-3 days (as with malaria);
  4. recurrent fever (febris recurrens) - unlike intermittent fever, the increase in temperature continues for several days, is replaced temporarily by normal temperature, followed by a new period of increase;
  5. hectic (exhaustive) fever (febris hectrica) with temperature fluctuations during the day of 3-5 °C (for example, with sepsis);
  6. undulating (febris undulans) with a gradual increase and decrease in maximum daily temperature increases;
  7. Irregular fever (febris irregularis) with irregular increases in temperature to various figures is the most common.

Measuring the temperature in the rectum has an independent significance. It is sometimes carried out by gynecologists who note an increase in temperature in women to subfebrile numbers in the second half of the menstrual cycle (after ovulation).

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