human body temperature - wikipedia, the free encyclopedia

Variations in body temperature are part of the circadian rhythm (see

at 4:30 and 19:00).

Human body temperatureHuman body temperatureHuman body temperatureHuman body temperatureFrom Wikipedia, the free encyclopedia

Normal human bodyNormal human bodyNormal human bodyNormal human bodytemperaturetemperaturetemperaturetemperature, also known asnormothermianormothermianormothermianormothermia or euthermiaeuthermiaeuthermiaeuthermia,depends upon the place in thebody at which themeasurement is made, thetime of day, as well as theactivity level of the person.Despite what manyschoolchildren are taught,there is no single number thatrepresents an idealtemperature for all people,under all circumstances, at anytime of day, and using anyplace of measurement.Instead, the body temperature of a healthy person changes slowly but constantly during thecourse of the day.

Different parts of the body have different temperatures. Rectal and vaginal measurements, ormeasurements taken directly inside the body cavity, are typically slightly higher than oralmeasurements, and oral measurements are somewhat higher than skin temperature. Thecommonly accepted average core body temperature (taken internally) is 37.0 °C (98.6 °F). Thetypical oral (under the tongue) measurement is slightly cooler, at 36.8° ± 0.4°C (98.2° ± 0.7°F),and temperatures taken in other places (such as under the arm or in the ear) produce different

typical numbers.[1]

Although some people think of these averages as representing the normal or

ideal temperature, a wide range of temperatures has been found in healthy people.[2]

In healthy adults, body temperature fluctuates about 0.5 °C (0.9 °F) throughout the day, withlower temperatures in the morning and higher temperatures in the late afternoon and evening, as

the body's needs and activities change.[1]

The time of day and other circumstances also affect thebody's temperature. The core body temperature of an individual tends to have the lowest value inthe second half of the sleep cycle; the lowest point, called the nadir, is one of the primary markersfor circadian rhythms. The body temperature also changes when a person is hungry, sleepy, orcold.

ContentsContentsContentsContents

1 Methods of measurement

2 Variations

2.1 Natural rhythms

2.2 Variations due to measurement methods

2.3 Variations due to outside factors

Human body temperature - Wikipedia, the free encyclopedia http://en.wikipedia.org/wiki/Human_body_temperature

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A medical/clinical thermometer

showing the temperature of

38.7 °C

3 Specific temperature concepts

3.1 Fever

3.2 Hyperthermia

3.3 Hypothermia

3.4 Basal body temperature

3.5 Core temperature

4 Human temperature variation effects

4.1 Hot

4.2 Normal

4.3 Cold

5 Measurement devices

6 References

Methods of measurementMethods of measurementMethods of measurementMethods of measurement

Taking a patient's temperature is an initial part of a full clinicalexamination. Sites used for measurement include:

In the anus (rectal temperature)

In the mouth (oral temperature)

Under the arm (axillary temperature)

In the ear (tympanic temperature)

In the vagina (vaginal temperature)

In the urethra (urethral temperature)

On the skin of the forehead

Over the temporal artery

The temporal artery can also be used. It is close to the surface of the skin and thereforeaccessible for reading. The temporal artery is part of the main trunk of the arterial system fromthe heart. So long as the patient’s blood flow is permanent and regular, the method allows precisemeasurement of the temperature.

VariationsVariationsVariationsVariations

Temperature control (thermoregulation) is part of a homeostatic mechanism that keeps theorganism at optimum operating temperature, as it affects the rate of chemical reactions. Inhumans the average internal temperature is 37.0 °C (98.6 °F), though it varies among individuals.However, no person always has exactly the same temperature at every moment of the day.Temperatures cycle regularly up and down through the day, as controlled by the person's circadianrhythm. The lowest temperature occurs about two hours before the person normally wakes up.

Additionally, temperatures change according to activities and external factors.[3]

In addition to varying throughout the day, normal body temperature may also differ as much as


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Diurnal variation in body temperature,

ranging from about 37.5 °C from 10

a.m. to 6 p.m., and falling to about

36.4 °C from 2 a.m. to 6 a.m.

0.5 °C (0.9 °F) from one day to the next, so that thehighest or lowest temperatures on one day will not alwaysexactly match the highest or lowest temperatures on thenext day.

Normal human body temperature varies slightly fromperson to person and by the time of day. Consequently,each type of measurement has a range of normaltemperatures. The range for normal human bodytemperatures, taken orally, is 36.8 ±0.5 °C

(98.2 ±0.9 °F).[4]

This means that any oral temperaturebetween 36.3 and 37.3 °C (97.3 and 99.1 °F) is likely tobe normal.

Natural rhythmsNatural rhythmsNatural rhythmsNatural rhythms

Body temperature normally fluctuates over the day, with the lowest levels around 4 a.m. and thehighest in the late afternoon, between 4:00 and 6:00 p.m. (assuming the person sleeps at night

and stays awake during the day).[4][1]

Therefore, an oral temperature of 37.3 °C (99.1 °F) would,strictly speaking, be a normal, healthy temperature in the afternoon but not in the early

morning.[1]

An individual's body temperature typically changes by about 0.5 °C (0.9 °F) between

its highest and lowest points each day.[1][4]

Body temperature is sensitive to many hormones, so women have a temperature rhythm that

varies with the menstrual cycle, called a circamensal rhythm.[3]

A woman's basal bodytemperature rises sharply after ovulation, as estrogen production decreases and progesteroneincreases. Fertility awareness programs use this predictable change to identify when a woman canbecome pregnant. During the luteal phase of the menstrual cycle, both the lowest and theaverage temperatures are slightly higher than during other parts of the cycle. However, theamount that the temperature rises during each day is slightly lower than typical, so the highest

temperature of the day is not very much higher than usual.[5]

Hormonal contraceptives bothsuppress the circamensal rhythm and raise the typical body temperature by about 0.6 °C

(1.1 °F).[3]

Temperature also varies with the change of seasons during each year. This pattern is called a

circannual rhythm.[5]

Studies of seasonal variations have produced inconsistent results. Peopleliving in different climates may have different seasonal patterns.

Increased physical fitness increases the amount of daily variation in temperature.[5]

With increased age, both average body temperature and the amount of daily variability in the

body temperature tend to decrease.[5]

Elderly patients may have a decreased ability to generatebody heat during a fever, so even a somewhat elevated temperature can indicate a seriousunderlying cause in geriatrics.

Variations due to measurement methodsVariations due to measurement methodsVariations due to measurement methodsVariations due to measurement methods

Different methods used for measuring temperature produce different results. The temperature


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reading depends on which part of the body is being measured. The typical daytime temperaturesamong healthy adults are as follows:

Temperature in the anus (rectum/rectal), vagina, or in the ear (otic) is about 37.5 °C

(99.5 °F)[6]

Temperature in the mouth (oral) is about 36.8 °C (98.2 °F)[4]

Temperature under the arm (axillary) is about 36.5 °C (97.7 °F) [6]

Generally, oral, rectal, gut, and core body temperatures, although slightly different, arewell-correlated, with oral temperature being the lowest of the four. Oral temperatures are

generally about 0.4 °C (0.7 °F) lower than rectal temperatures.[1]

Oral temperatures are influenced by drinking, chewing, smoking, and breathing with the mouthopen. Cold drinks or food reduce oral temperatures; hot drinks, hot food, chewing, and smoking

raise oral temperatures.[3]

Axillary (armpit), tympanic (ear), and other skin-based temperatures correlate relatively poorly

with core body temperature.[5]

Tympanic measurements run higher than rectal and core body

measurements, and axillary temperatures run lower.[5]

The body uses the skin as a tool toincrease or decrease core body temperature, which affects the temperature of the skin.

Skin-based temperatures are more variable than other measurement sites.[5]

The peak daily

temperature for axillary measurements lags about three hours behind the rest of the body.[5]

Skintemperatures are also more influenced by outside factors, such as clothing and air temperature.

Variations due to outside factorsVariations due to outside factorsVariations due to outside factorsVariations due to outside factors

Many outside factors affect the measured temperature as well. "Normal" values are generallygiven for an otherwise healthy, non-fasting adult, dressed comfortably, indoors, in a room that iskept at a normal room temperature (22.7 to 24.4 °C or 73 to 76 °F), during the morning, but notshortly after arising from sleep. Furthermore, for oral temperatures, the subject must not haveeaten, drunk, or smoked anything in at least the previous fifteen to twenty minutes, as thetemperature of the food, drink, or smoke can dramatically affect the reading.

Temperature is increased after eating or drinking anything with calories. Caloric restriction, as for

a weight-loss diet, reduces overall body temperature.[3]

Drinking alcohol reduces the amount ofdaily change, slightly lowering daytime temperatures and noticeably raising nighttime

temperatures.[3]

Exercise raises body temperatures. In adults, a noticeable increase usually requires strenuousexercise or exercise sustained over a significant time. Children develop higher temperatures withmilder activities, like playing.

Psychological factors also influence body temperature: a very excited person often has an elevatedtemperature.

Wearing more clothing slows daily temperature changes and raises body temperature.[3]

Similarly,

sleeping with an electric blanket raises the body temperature at night.[3]


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Sleep disturbances also affect temperatures. Normally, body temperature drops significantly at aperson's normal bedtime and throughout the night. Short-term sleep deprivation produces ahigher temperature at night than normal, but long-term sleep deprivation appears to reduce

temperatures.[3]

Insomnia and poor sleep quality are associated with smaller and later drops in

body temperature.[3]

Similarly, waking up unusually early, sleeping in, jet lag and changes to shift

work schedules may affect body temperature.[3]

Specific temperature conceptsSpecific temperature conceptsSpecific temperature conceptsSpecific temperature concepts

FeverFeverFeverFever

A temperature setpoint is the level at which the body attempts to maintain its temperature. Whenthe setpoint is raised, the result is a fever. Most fevers are caused by infectious disease and canbe lowered, if desired, with antipyretic medications.

An early morning temperature higher than 37.2 °C (> 98.9°F) or a late afternoon temperaturehigher than 37.7 °C (> 99.9°F) is normally considered a fever, assuming that the temperature is

elevated due to a change in the hypothalamus's setpoint.[1]

Lower thresholds are sometimes

appropriate for elderly people.[1]

The normal daily temperature variation is typically 0.5 °C

(0.9°F), but can be greater among people recovering from a fever.[1]

An organism at optimum temperature is considered afebrile or apyrexic, meaning "without fever".If temperature is raised, but the setpoint is not raised, then the result is hyperthermia.

HyperthermiaHyperthermiaHyperthermiaHyperthermia

Hyperthermia occurs when the body produces or absorbs more heat than it can dissipate. It isusually caused by prolonged exposure to high temperatures. The heat-regulating mechanisms ofthe body eventually become overwhelmed and unable to deal effectively with the heat, causingthe body temperature to climb uncontrollably. Hyperthermia at or above about 40 °C (104 °F) is alife-threatening medical emergency that requires immediate treatment. Common symptomsinclude headache, confusion, and fatigue. If sweating has resulted in dehydration, then theaffected person may have dry, red skin.

In a medical setting, mild hyperthermia is commonly called heat exhaustion or heat prostration;severe hyperthermia is called heat stroke. Heat stroke may come on suddenly, but it usuallyfollows the untreated milder stages. Treatment involves cooling and rehydrating the body; fever-reducing drugs are useless for this condition. This may be done through moving out of directsunlight to a cooler and shaded environment, drinking water, removing clothing that might keepheat close to the body, or sitting in front of a fan. Bathing in tepid or cool water, or even justwashing the face and other exposed areas of the skin, can be helpful.

With fever, the body's core temperature rises to a higher temperature through the action of thepart of the brain that controls the body temperature; with hyperthermia, the body temperature israised without the consent of the heat control centers.

HypothermiaHypothermiaHypothermiaHypothermia


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In hypothermia, body temperature drops below that required for normal metabolism and bodilyfunctions. In humans, this is usually due to excessive exposure to cold air or water, but it can bedeliberately induced as a medical treatment. Symptoms usually appear when the body's coretemperature drops by 1-2 °C (1.8-3.6 °F) below normal temperature.

Basal body temperatureBasal body temperatureBasal body temperatureBasal body temperature

Basal body temperature is the lowest temperature attained by the body during rest (usually duringsleep). It is generally measured immediately after awakening and before any physical activity hasbeen undertaken, although the temperature measured at that time is somewhat higher than thetrue basal body temperature. In women, temperature differs at various points in the menstrualcycle, and this can be used in the long-term to track ovulation both for the purpose of aidingconception or avoiding pregnancy. This process is called fertility awareness.

Core temperatureCore temperatureCore temperatureCore temperature

Core temperatureCore temperatureCore temperatureCore temperature, also called core body temperaturecore body temperaturecore body temperaturecore body temperature, is the operating temperature of anorganism, specifically in deep structures of the body such as the liver, in comparison totemperatures of peripheral tissues. Core temperature is normally maintained within a narrowrange so that essential enzymatic reactions can occur. Significant core temperature elevation(hyperthermia) or depression (hypothermia) that is prolonged for more than a brief period of timeis incompatible with human life.

Temperature examination in the rectum is the traditional gold standard measurement used toestimate core temperature (oral temperature is affected by hot or cold drinks and mouth-breathing). Rectal temperature is expected to be approximately one Fahrenheit degree higherthan an oral temperature taken on the same person at the same time. Ear thermometers measureeardrum temperature using infrared sensors. The blood supply to the tympanic membrane isshared with the brain. However, this method of measuring body temperature is not as accurate asrectal measurement and has a low sensitivity for fevers, missing three or four out of every ten

fevers in children.[7]

Ear temperature measurement may be acceptable for observing trends inbody temperature but is less useful in consistently identifying fevers.

Until recently, direct measurement of core body temperature required surgical insertion of aprobe, so a variety of indirect methods have commonly been used. The rectal or vaginaltemperature is generally considered to give the most accurate assessment of core bodytemperature, particularly in hypothermia. In the early 2000s, ingestible thermistors in capsuleform were produced, allowing the temperature inside the digestive tract to be transmitted to anexternal receiver; one study found that these were comparable in accuracy to rectal temperature

measurement.[8]

Human temperature variation effectsHuman temperature variation effectsHuman temperature variation effectsHuman temperature variation effects

HotHotHotHot

Fevers are not to be confused with heat stroke. In fever the person can feel cold at high bodytemperatures. One theory is that the body is fooled into thinking it is cold by the infectantmicrobe. The more recent alternative hypothesis is that fever is a constructive response toinfection, and that the chills are an evolutionary mechanism whose function is to motivate


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individuals to seek warmth, to help facilitate the increase in body temperature.

44 °C (111 °F) or more44 °C (111 °F) or more44 °C (111 °F) or more44 °C (111 °F) or more - Almost certainly death will occur; however, patients have been

known to survive up to 46.5 °C (115.7 °F).[9]

43 °C (109 °F)43 °C (109 °F)43 °C (109 °F)43 °C (109 °F) - Normally death, or there may be serious brain damage, continuous

convulsions and shock. Cardio-respiratory collapse will likely occur.

42 °C (108 °F)42 °C (108 °F)42 °C (108 °F)42 °C (108 °F) - Subject may turn pale or remain flushed and red. They may become

comatose, be in severe delirium, vomiting, and convulsions can occur. Blood pressure may

be high or low and heart rate will be very fast.

41 °C (106 °F)41 °C (106 °F)41 °C (106 °F)41 °C (106 °F) - (Medical emergency) - Fainting, vomiting, severe headache, dizziness,

confusion, hallucinations, delirium and drowsiness can occur. There may also be palpitations

and breathlessness.

40 °C (104 °F)40 °C (104 °F)40 °C (104 °F)40 °C (104 °F) - Fainting, dehydration, weakness, vomiting, headache and dizziness may

occur as well as profuse sweating. Starts to be life-threatening.

39 °C (102 °F)39 °C (102 °F)39 °C (102 °F)39 °C (102 °F) - Severe sweating, flushed and red. Fast heart rate and breathlessness.

There may be exhaustion accompanying this. Children and people with epilepsy may be very

likely to get convulsions at this point.

38 °C (100 °F)38 °C (100 °F)38 °C (100 °F)38 °C (100 °F) -(this is classed as hyperthermia if not caused by a fever) Feeling hot,

sweating, feeling thirsty, feeling very uncomfortable, slightly hungry. If this is caused by

fever, there may also be chills.

NormalNormalNormalNormal

37 °C37 °C37 °C37 °C ( ( ( (98.6 °F98.6 °F98.6 °F98.6 °F)))) - Normal internal body temperature (which varies between about

36.12–37.5 °C (97.02–99.50 °F))

ColdColdColdCold

36 °C (97 °F)36 °C (97 °F)36 °C (97 °F)36 °C (97 °F) - Feeling cold, mild to moderate shivering (body temperature may drop this

low during sleep). May be a normal body temperature.

35 °C (95 °F)35 °C (95 °F)35 °C (95 °F)35 °C (95 °F) - (Hypothermia is less than 35 °C (95 °F)) - Intense shivering, numbness and

bluish/grayness of the skin. There is the possibility of heart irritability.

34 °C (93 °F)34 °C (93 °F)34 °C (93 °F)34 °C (93 °F) - Severe shivering, loss of movement of fingers, blueness and confusion.

Some behavioural changes may take place.

33 °C (91 °F)33 °C (91 °F)33 °C (91 °F)33 °C (91 °F) - Moderate to severe confusion, sleepiness, depressed reflexes, progressive

loss of shivering, slow heart beat, shallow breathing. Shivering may stop. Subject may be

unresponsive to certain stimuli.

32 °C (90 °F)32 °C (90 °F)32 °C (90 °F)32 °C (90 °F) - (Medical emergency) Hallucinations, delirium, complete confusion, extreme

sleepiness that is progressively becoming comatose. Shivering is absent (subject may even

think they are hot). Reflex may be absent or very slight.

31 °C (88 °F)31 °C (88 °F)31 °C (88 °F)31 °C (88 °F) - Comatose, very rarely conscious. No or slight reflexes. Very shallow


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breathing and slow heart rate. Possibility of serious heart rhythm problems.

28 °C (82 °F)28 °C (82 °F)28 °C (82 °F)28 °C (82 °F) - Severe heart rhythm disturbances are likely and breathing may stop at any

time. Patient may appear to be dead.

24–26 °C (75–79 °F) or less24–26 °C (75–79 °F) or less24–26 °C (75–79 °F) or less24–26 °C (75–79 °F) or less - Death usually occurs due to irregular heart beat or

respiratory arrest; however, some patients have been known to survive with body

temperatures as low as 14.2°C (57.5°F).[9]

Measurement devicesMeasurement devicesMeasurement devicesMeasurement devices

There is a risk of injury from cracking glass thermometersglass thermometersglass thermometersglass thermometers if too much force is applied by theteeth to hold them in place, and the alcohol or mercury contents are poisonous. These olderthermometers are gradually being replaced by electronic thermometerselectronic thermometerselectronic thermometerselectronic thermometers which are made fromsolid plastic and use a metal (thermocouple) sensor.

A plastic thermometer stripplastic thermometer stripplastic thermometer stripplastic thermometer strip placed on the forehead gives an approximate local reading, whichdepends to a great extent on ambient air temperature and local circulation effects. Using athermometer to record the temperature under the armpit is less affected by surrounding airtemperature, but is still prone to diverge from true core temperature if there are alterations inblood circulation.

Since 2000, small ear thermometersear thermometersear thermometersear thermometers have become available. It is thought that the eardrumclosely mirrors core temperature values, and these devices work by detecting the infrared heatemission from the tympanic membrane. A measurement is quickly taken within one second,making them popular for use with children. While the electronic display of the temperature valueis easier to read than interpreting the graduation marks on a thermometer, there are some

concerns about the accuracy of ear thermometers in home use.[10]

ReferencesReferencesReferencesReferences

^ aaaa bbbb cccc dddd eeee ffff gggg hhhh iiii Harrison's principles of internal medicine. (http://accessmedicine.com

/resourceTOC.aspx?resourceID=4) (18th ed. ed.). New York: McGraw-Hill. 2011. p. 142.

ISBN 978-0-07-174889-6.

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^̂̂̂ Laupland KB (July 2009). "Fever in the critically ill medical patient". Crit. Care Med. 37373737 (7 Suppl):

S273–8. doi:10.1097/CCM.0b013e3181aa6117 (http://dx.doi.org

/10.1097%2FCCM.0b013e3181aa6117). PMID 19535958 (https://www.ncbi.nlm.nih.gov/pubmed

/19535958).

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^ aaaa bbbb cccc dddd eeee ffff gggg hhhh iiii jjjj kkkk Kelly GS (March 2007). "Body temperature variability (Part 2): masking influences

of body temperature variability and a review of body temperature variability in disease". Altern Med

Rev 12121212 (1): 49–62. PMID 17397267 (https://www.ncbi.nlm.nih.gov/pubmed/17397267).

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^ aaaa bbbb cccc dddd Mackowiak, P. A.; S. S. Wasserman; M. M. Levine (1992-09-23). "A critical appraisal of 98.6

degrees F, the upper limit of the normal body temperature, and other legacies of Carl Reinhold August

Wunderlich" (http://jama.ama-assn.org/cgi/content/abstract/268/12/1578). JAMA 268268268268 (12):

1578–1580. doi:10.1001/jama.268.12.1578 (http://dx.doi.org/10.1001%2Fjama.268.12.1578).

PMID 1302471 (https://www.ncbi.nlm.nih.gov/pubmed/1302471). Retrieved 2007-08-22.

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^ aaaa bbbb cccc dddd eeee ffff gggg hhhh Kelly G (December 2006). "Body temperature variability (Part 1): a review of the history

of body temperature and its variability due to site selection, biological rhythms, fitness, and aging".

Altern Med Rev 11111111 (4): 278–93. PMID 17176167 (https://www.ncbi.nlm.nih.gov/pubmed/17176167).

5.

^ aaaa bbbb Elert, Glenn (2005). "Temperature of a Healthy Human (Body Temperature)"

(http://hypertextbook.com/facts/LenaWong.shtml). The Physics Factbook. Retrieved 2007-08-22.

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^̂̂̂ Dodd SR, Lancaster GA, Craig JV, Smyth RL, Williamson PR (April 2006). "In a systematic review,

infrared ear thermometry for fever diagnosis in children finds poor sensitivity". J Clin Epidemiol 59595959 (4):

354–7. doi:10.1016/j.jclinepi.2005.10.004 (http://dx.doi.org/10.1016%2Fj.jclinepi.2005.10.004).

PMID 16549256 (https://www.ncbi.nlm.nih.gov/pubmed/16549256).

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^̂̂̂ J.E. McKenzie, D.W. Osgood, Validation of a new telemetric core temperature monitor

(http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T94-4DDXMRG-H&_user=10&

_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=957411958&

_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&

md5=6c571acbee07e8999b4e7774d3212dee), Journal of Thermal Biology, Volume 29, Issues 7–8,

October–December 2004, Pages 605–611, ISSN 0306-4565, doi 10.1016/j.jtherbio.2004.08.020.

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^ aaaa bbbb Excerpt: Humans, Body Extremes (http://www.powells.com/biblio?show=0553587129&

page=excerpt). Guinness World Records. 2004. Retrieved 24 October 2013.

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^̂̂̂ Robinson JL, Jou H, Spady DW (January 2005). "Accuracy of parents in measuring body temperature

with a tympanic thermometer" (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC545063). BMC Fam

Pract 6666: 3. doi:10.1186/1471-2296-6-3 (http://dx.doi.org/10.1186%2F1471-2296-6-3). PMC 545063

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