What's the average human body temperature—and is it cooling down?

The common belief that human bodies run at 98.6°F (37°C) appears to be wrong, and some evidence suggests our temperatures have decreased over time.

For 150 years, 98.6 degrees Fahrenheit was thought to be the average body temperature for a healthy human being. But that number is wrong.

But for at least the past two decades, researchers have known that the average body temperature is actually colder, about 97.8 degrees Fahrenheit, and that anywhere between 96.3 and 99.3 degrees Fahrenheit is within a normal range for the human body. Yet 98.6 has endured as the magic number among concerned parents and doctors alike, displayed on everything from drugstore thermometers to medical centers’ webpages.

“Doctors are no different from anybody else,” says Julie Parsonnet, an infectious disease doctor at Stanford University. “We’ve been raised with that as the normal value since we were little.”

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