Blood outside the body will remain at the same temperature, but only for a short time. After a few hours, the blood cells will die, and the blood will then reach room temperature.
As your body temperature changes, so does the temperature of your blood. These changes are due to various internal and external factors but typically decrease with age.
What is the optimal blood temperature?
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In the 19th century, a German doctor named Carl Wunderlich identified an average body temperature of 98.6°F. However, we now know that this is not always true.
For example, a 2019 review found that the average body temperature is 97.86°F. However, this is just an average, and many things can affect your body temperature, including:
activity levels
age
the time of day
biological sex
An adult’s body temperature changes depending on various factors, but the most significant changes depend on your age and where you take the measurement from.
For example, people younger than ages 60 years have higher body temperatures than those ages 60–65 years and older. Body temperature readings in all ages differ according to where the temperature reading was taken, which include:
rectal measurement
armpit measurement
oral measurement
Armpit measurements may be over 1 degree lower than those taken by mouth, and rectal temperatures are typically up to a degree higher than oral measurements.
How does your body regulate temperature?
Your body’s temperature may change throughout the day based on what you’re doing, like exercising, sleeping, or eating.
If your body temperature gets too high or too low, a part of your brain called the hypothalamus uses a process known as thermoregulation to get your temperature back to optimal levels.
The body uses different mechanisms during thermoregulation, including vasodilation (widening blood vessels), vasoconstriction (narrowing blood vessels), sweating, and hormonal thermogenesis (burning hormonal calories for heat).
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If you have a fever, your body will try to reduce your temperature through sweating or vasodilation. During vasodilation, your blood vessels grow larger to increase the blood flow through your body, which ultimately cools you down.
You can usually treat a mild fever at home with fever-reducing medication like ibuprofen (Advil) or acetaminophen (Tylenol). Adults with fevers above 103°F (39.4°C) should consider contacting a doctor.
Heat stroke
You may experience heat stroke if your body’s temperature gets too high and you can’t regulate it. It usually results in rapid heart rate and hot skin. In some cases, you also can lose consciousness.
Causes of heat stroke may include:
drinking alcohol
dehydration
wearing heavy clothing
Heat stroke can be very dangerous. If you think you might be experiencing heat stroke, you should seek immediate medical treatment.
Adults ages 65 and over are more susceptible to heat-related health conditions because the body cannot regulate temperature as well.
Low body temperatures
Low body temperatures are generally due to being in cold conditions, and, as with heat, older adults are more sensitive to cold temperatures due to difficulties regulating body temperature. Other reasons you may feel the cold more include:
alcohol use
adult drug use
shock
diabetes
hypothyroidism
Your body uses vasoconstriction to manage lower temperatures. During vasoconstriction, the blood vessels under your skin will shrink to decrease the blood flow and help you retain heat.
You may also begin shivering. Shivering is a muscular reaction that generates heat to warm you up.
You should not be too concerned if low body temperature is your only symptom, as you will usually warm back up once you can take steps to increase your body heat. This could be going inside somewhere warm, adding additional layers of clothing, or using personal heating products like hot water bottles.
However, low body temperature can sometimes signify a health condition, especially if you’re experiencing feeling cold alongside other symptoms like:
chills
tremors
confusion
difficulty breathing
In these instances, it is best to seek immediate medical attention.
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Summary
Blood and body temperature are similar. For adults, a typical temperature is around 98.6℉, although this can vary.
Various factors can affect blood and body temperature, including age, time of day, and activity levels, but temperature ranges are also different depending on your age.
People under the age of 60 years have higher body temperatures than those around 60–65 years and older.
How you take the reading – by mouth, armpit, forehead, or rectally – can also affect your temperature reading.
