It’s a fact that is still taught daily to schoolchildren all over the world: Normal human body temperature is 98.6 degrees Fahrenheit. But as with most measurements, “normal” has a range. With current technology, don’t be surprised if your actual measure temperature is rarely 98.6. That’s because “normal” temperature was based on the average temperature of hundreds of people using oral, mercury thermometers. Current thermometers are not only much faster, they are much more accurate and document two things known even in the days of mercury thermometers: There is variability in body temperature over the course of the day, and there is variability between different people.
In fact, from what is now known, the case could be made to abandon 98.6 as the definition of normal body temperature and instead recognize the range of normal. Thermoregulation — the body’s mechanisms to maintain body temperature within a certain range — is a key bodily function, but it does allow perfectly healthy persons to drift higher or lower than 98.6 rather often.