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Human Body Temperature

Human Body Temperature

It is widely-accepted that the normal body temperature in humans is 37.0° C (98.6° F). However, this value may vary with different factors like age, health condition, time, degree of physical activities, etc.
Sonia Nair
Last Updated: Apr 19, 2018
It is a common fact that humans are warm-blooded and that the human body has various ways of regulating its temperature. For example, during extreme cold, the body generates heat by shivering, whereas in hot conditions, the body temperature is brought down through sweating. This regulation mechanism called homeostasis, helps the body to maintain a normal temperature.
The normal human body temperature range was deduced by a German physician, Dr. Carl Wunderlich during the 19th century. According to his studies, the normal body temperature is 37° C (98.6° F). However, the findings of Dr. Wunderlich was challenged, as subsequent studies came up with variations in this value. It has been observed that the normal body temperature may vary with various factors, like age, gender, time, method of measurement, etc.
Variations in Normal Body Temperature
Method of Measurement
Mouth (oral) and underarms (axillary) are the most commonly used locations to read body temperature. Apart from that, other sites that are used for this purpose are the ear canal, rectum, vagina and forehead. The fact is that the readings may not be the same in all cases. In other words, the body temperature may slightly vary from one location to another.
  • Oral Temperature - 35.7 to 37.5° C (96.2 to 99.5° F)
  • Tympanic Temperature - 35.7 to 38° C (96.2 to 100.4° F)
  • Rectal Temperature - 36.2 to 38.1° C (97.2 to 100.6° F)
  • Armpit Temperature - 34.7 to 37.2° C (94.5 to 99° F)
These are only rough estimates, as these values may again vary with gender, age, health condition, time, etc. However, it can be observed that the highest among the given values is the rectal temperature, followed by oral and tympanic (both are almost similar) ones, which are slightly higher than the armpit or axillary temperatures. Oral temperature range may fluctuate, if taken right after drinking or eating something that is very cold or hot. While intake of cold foods may slightly lower the oral temperature, hot foods may increase it.
Time of Measurement
Another important factor that can affect the normal human body temperature is time. In other words, body temperature may fluctuate throughout the day. In normal adults, the highest values are usually recorded between 4:00 and 6:00 in the afternoon, whereas the lowest values are recorded right after sleep, early in the morning. This finding is applicable for those who follow the normal day-night pattern (who sleep during the night and stay awake during the day). Usually, a maximum variation of 0.5 to 1° C can be seen, if you compare the readings taken in the afternoon and those taken during early morning. In this case too, the values may fluctuate with factors like level of physical activities. It is also said that change in seasons and the resultant climatic variations may affect the normal body temperature in humans.
Body temperature variation
Image Source:Wikimedia Commons (PD)
Age and Gender
In general, it is believed that women tend to have a slightly higher body temperature, when compared to men. In case of women, the hormonal variations throughout the menstrual cycle is a factor that affects the body temperature. This explains the rise in basal body temperature (lowest body temperature during rest, usually measured early in the morning, after sleep) after ovulation, when the level of progesterone increases. Core temperature is another term that refers to the temperature of the inner organs, like the liver. Rectal or vaginal temperature is said to be closest to the core temperature.

When compared to healthy adults, elderly people have a slightly lower body temperature. According to a recent study conducted in elderly people (in their eighties), it has been found that the average body temperature is below 37° C. The ability to produce body heat is lesser in old age and so, a slightly higher body temperature may indicate fever.
  • Those in the age group of 0 to 24 months have a normal body temperature that ranges between 34.7 to 38° C (94.5 to 100.4° F).
  • Kids in the age group of three to ten years have a normal body temperature of 35.5 to 38° C (95.9 to 100.4° F).
  • The value increases to 35.2 to 38° C (95.4 to 100.4° F) in those belonging to the age group of 11 to 65 years.
  • Above the age of 65, the human body temperature could be between 35.6 to 37.5° C (96 to 99.5° F).
These values may vary slightly with the different methods of measurement, gender, health condition and other factors.
Other Factors
Apart from those discussed above, there are some other factors that are found to cause slight fluctuations in body temperature.
  • It may happen that the body temperature increases after consumption of food (especially food with high calories) and during physical activities.
  • Fasting lowers the body temperature. Consumption of alcoholic drinks may cause slight decrease in body temperature during daytime and a slight rise in temperature during night.
  • While lack of sleep is one of the reasons for decrease in body temperature, a state of excitement may sometimes cause rise in body temperature.
To conclude, it may not be accurate to represent the human body temperature with a single value that is common for all. There are various factors that affect this value. While slight variations are considered normal, any drastic rise or dip can be dangerous.
Too High or Low Body Temperatures
An abnormal increase in the normal human body temperature is called hyperthermia and a drastic dip is called hypothermia. Both conditions can cause mild to severe and life-threatening symptoms. The symptoms of hypothermia usually appear as the core temperature drops by 1 to 2° C. The condition may worsen with a further dip in body temperature and the affected person develops life-threatening symptoms, as it drops beyond 33° C. A body temperature that is above 38° C is hyperthermia. The symptoms can be life-threatening as the temperature rises beyond 40° C. In that case, the condition is called heat stroke.

Though both hyperthermia and fever refer to a rise in body temperature, the conditions differ. A body temperature of 37.2° C during early morning and 37.7° C during the afternoon, can be considered fever. In case of fever, the rise in body temperature is due to a change in the setting of the thermoregulatory center in the body, which is not the case with hyperthermia. Medication used for fever do not lower the temperature in those with hyperthermia, as these drugs work on the setting of the thermoregulatory center and bring it back to normal.
So the normal body temperature may slightly vary with other factors. In case of any abnormal rise or dip in body temperature, immediate medical attention must be sought, so as to avoid complications.