Body temperature

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The body temperature is the temperature of a human or animal body . As a rule, this refers to the temperature of the inside of the body, the core body temperature , more rarely the surface temperature of the skin. The core body temperature describes the temperature of the vital internal organs.

Homoiothermal (equally warm) living beings regulate the body temperature towards a constant setpoint . Poikilothermic ( cold-blooded ) living beings do not have a constant body temperature. A temporary increase in the temperature setpoint in homoiothermic creatures such as humans is called fever (Latin: Febris ), and a decrease below the setpoint is called hypothermia (low temperature).

There are various measuring devices for determining the body temperature of a person. In the private sector, classic clinical thermometers are widely used, which are usually used axillary (under the armpit ), orally (in the mouth ) or rectally (in the rectum ), with the rectal method measuring the core body temperature most precisely. In the clinical area, pyrometers can more often be found that enable contactless body temperature measurement in the ear. Temperature measurements in the blood, in the esophagus or in the urinary bladder are also possible.

The human being

Nocturnal body temperature curve of a person

In humans , the normal core body temperature averages 36.6 ° C. 95% of all people have a temperature of 35.7 to 37.3 ° C. The mean body temperature decreases with increasing age by 0.021 ° C per decade. Overweight people have a higher body temperature.

Measurement of core body temperature

The body temperature can be assessed by palpation and determined more precisely with a clinical thermometer. Common measurement points are the mouth, armpit or rectum, with the rectal value being closest to the core body temperature. The temperature under the tongue is about 0.3–0.5 ° C lower; the one under the armpits is about 0.5 ° C lower and relatively unreliable. Modern measuring devices (pyrometers) also allow non-contact measurements in a matter of seconds and, in principle, accurate measurements in the ear , which, however, deliver incorrectly low values in the event of incorrect operation due to incorrect angulation and relocation of the ear canal by ear wax . For specific questions, the core body temperature can be measured using certain catheters . In intensive care , z. B. Measurements in the urinary bladder or via central venous catheters are common.

Normal fluctuations in core body temperature

The core body temperature fluctuates within narrow limits throughout the day: it is lower at night than during the day; during physical activity it increases by up to two degrees Celsius. The normal fluctuation during the day typically has a morning minimum (rectally about 36.5 ° C) and a maximum in the afternoon (rectal 37.8 ° C). During sleep, a minimum occurs around 2 a.m. (seen over the entire 24 hours); the temperature then rises slightly again before waking up.

In women, the temperature fluctuates by around half a degree ( basal temperature ) over the monthly cycle .

Temperature table

In a table overview, the temperature ranges in adults can be subdivided as follows:

Body temperature designation
below 20 ° C Cold death
below 27 ° C can be fatal, extreme bradycardia
33 ° C With cooling ( hypothermia )
35 ° C Undertemperature
36.3 to 37.4 ° C Normal temperature (afebrile)
37.5 to 38.0 ° C elevated temperature (subfebrile)
38.1 to 38.5 ° C mild fever (febrile)
38.6 to 39.0 ° C fever
39.1 to 39.9 ° C high fever
40 to 42 ° C very high fever (hyperpyretic fever), convulsions
42 ° C Circulatory failure
from 44 ° C Death from denaturation of proteins or enzymes

A body temperature above 40 ° C can lead to death. The upper limit of survival is approx. 44 ° C, the lower limit approx. 20 ° C. In children, especially those who are predisposed to the rapid rise in body temperature above 38.5 ° C, febrile seizures can occur.


The body tries to maintain the target temperature in the core of the body as long as possible, e.g. B. by reducing the heat output in the case of hypothermia through reduced blood flow to the skin and extremities or by producing heat through rhythmic contraction of the muscles in the form of a chill . In the case of fever, increased blood flow and sweating increase the heat output. Further mechanisms are given under thermoregulation .

Hypothermia in medicine

Some major surgical interventions are performed in hypothermia after lowering the core body temperature in order to reduce the brain's oxygen demand and thereby achieve protection of the brain ( neuroprotection ). Mild hypothermia is also used in neurological intensive care medicine after brain damage with a similar objective. However, this procedure is controversial because complications such as susceptibility to infection and wound healing disorders can also occur. There is no medical evidence for the effectiveness of hypothermia in the treatment of traumatic brain injury (status 2004).

The strongest, scientifically proven hypothermia due to an accident was a body temperature of 13.7 degrees; the accident victim Anna Bågenholm could still be reanimated without permanent damage.

Body temperature during exercise

It is known from sports science that people have an increased body temperature during intense exercise. During a marathon, for example, the body temperature rises to around 39 ° C. Since cooling down the body during physical exertion is associated with high energy consumption, competitive sports systematically try to cool down the body temperature before the competition and, if necessary, during breaks (including half-time).

Conversely, an increased body temperature is also a prerequisite for maximum physical performance. The warm-up , connected with an increase in body temperature to 38.5 39 ° C, improved various physiological processes. After a systematic warm-up of 15 to 30 minutes, especially before high-speed performances (sprint, basketball) and sports with maximum effort (rowing, weight training), 4 to 7% higher performance was observed. In addition, the risk of injury is reduced.

Even when you are in a sauna , your body temperature quickly rises to around 39 ° C. The body can only keep its temperature in the 60 to 100 ° C hot air for a short time through intensive sweating from a further increase. For this reason, the recommended duration of a sauna session must not be exceeded.

Temperature in the body shell

Strictly speaking, only the core body temperature is constant in humans. The temperature outside the core of the body, in the so-called body shell, can be significantly lower. The thickness of the shell and also its temperature fluctuates with the outside temperature. The regulation takes place through varying degrees of blood flow and corresponding cooling with a reduced blood supply. At pleasant ambient temperatures, the mean skin temperature is around 32–34 ° C. With an air temperature of 15 ° C, the mean skin temperature is only around 24 ° C, the finger temperature drops to around 16 ° C. The temperature in the fingers and toes can even drop to 5 ° C for a short time without causing permanent damage.

Animal kingdom

There are cold-blooded animals whose body temperature depends on the respective ambient temperature and the circulatory activity (e.g. worms , insects , amphibians and reptiles ) and animals of the same temperature that keep their body temperature largely constant regardless of the ambient heat and physical activity. These include birds and mammals, including humans, and presumably some extinct dinosaurs ; body temperatures of approx. 32 and 37 degrees were reconstructed for two groups of non-avian dinosaurs. Birds are those animals of the same temperature with the highest body temperature - it is 38 to 42 ° C. Individual reptile species such as the desert iguana are able to cope with temporary body warming to over 47 ° C unharmed.


Many birds can lower their body temperature significantly in a special sleep state ( torpor ), although they are evenly warm. In this way, energy consumption can be greatly reduced at night due to a lower temperature difference compared to the surroundings. Hummingbirds and common swifts drop their body temperature from typically 40 ° C to as low as 18 ° C, which is a considerable temperature difference. In hummingbirds and other small birds with a fast metabolism, this energy-saving sleep state enables them to spend the night without further feeding. Many birds are also able to reduce energy losses during temporary bad weather.


Most mammals are only able to do this to a very limited extent, usually only a few degrees Celsius. Few mammals hold as the hedgehog a true hibernation with long lowered body temperature. However , a whole range of mammals seem to be able to keep a hibernation in cold weather and limited food supply. According to the latest research results on deer and roe deer, these animals can also lower their body temperature significantly over several hours every day if necessary.


The normal body temperature of healthy horses is 38.8 to 39.3 ° C in newborn foals up to the 5th day, thereafter 38 to 39 ° C in foals and 37.3 to 38.0 ° C in adult horses (in Quiet). During exertion, the body temperature of an adult horse is max. 41 ° C.


The body temperature of a healthy cattle is 38.3 to 38.8 ° C (calf up to 39.2 ° C)


Adult cats have a normal temperature of 38.3 to 39.0 ° C. Internal body temperatures above 39 ° C (hyperthermia) are usually the result of infectious diseases or inflammation. Heat build-up during transport in an unsuitable container, excitement or cramps can also trigger hyperthermia in cats. Low temperatures (hypothermia) can indicate a general decline in vital functions, and they also occur as a result of anesthetic aftereffects. Young cats have a lower internal body temperature of 37 to 38.2 ° C in the first three weeks of life. From the 7th week of life at the latest, the value adapts to the normal range of adult animals.

More mammals

In the rectum measured temperature is from dog and rat at 37.5 to 38.5 ° C, wherein the shrew at 34.0 to 37.0 ° C, at Seebären at 37.0 to 38.5 ° C and at platypus only at 31.0 - 33.0 ° C.


Bumblebees are able to raise their body temperature above the ambient temperature through the activity of the muscles and thus be active even when the outside temperature is low. State-forming insects regulate their body temperature and that of the nest through social behavior. Bees , wasps and ants , among others , can increase the temperature of the colony through joint muscle activity and the introduction of heat, e.g. through animals warmed up in the sun. Water is often introduced for cooling. The regulation of the temperature to a stable level is carried out by many individuals; individual animals would not be able to do this in this form. The silver ant can withstand a body temperature of just under 54 ° C.

See also


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  3. - ( Memento of the original from September 28, 2007 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Health tip "Fever" (PDF) @1@ 2Template: Webachiv / IABot /
  4. So at least the information in the "Health Lexicon of the Barmer" , whereby the temperature maximum is again strongly dependent on the activity of the person.
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  9. Michael Gekle, Dominique Singer: Heat balance and temperature regulation . In: Hans-Christian Pape, Armin Kurtz, Stefan Silbernagl (eds.): Physiology . 7th edition. Georg Thieme Verlag, Stuttgart 2014, ISBN 978-3-13-796007-2 , Chapter 13, p. 566-584 .
  10. ^ Robert F. Schmidt , Florian Lang, Manfred Heckmann: Physiologie des Menschen. with pathophysiology . 31st edition. SpringerMedizin Verlag, Heidelberg 2010, ISBN 978-3-642-01650-9 , p. 834-853 . , Chapter 39 by Pontus B. Persson: Energy and heat balance, thermoregulation.
  11. Robert A. Eagle et al .: Isotopic ordering in eggshells reflects body temperatures and suggests differing thermophysiology in two Cretaceous dinosaurs. In: Nature Communications. Volume 6, Article No. 8296, 2015, doi: 10.1038 / ncomms9296
    How to take a dinosaur's temperature. On: of October 13, 2015.
  12. WW Mayhew (1968), cit. in: Albert F. Bennett & William R. Dawson: Aerobic and Anaerobic Metabolism during Activity in the Lizard Dipsosaurus dorsalis. - J.comp. Physiol. 81: 289-299 (1972). Springer publishing house.
  13. Article on 3sat .
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