How 98.6°F became a benchmark
The familiar number traces to 19th-century measurements by German physician Carl Wunderlich. He took temperatures from many people and helped establish 98.6°F (37°C) as a useful average. It was never a precise boundary separating healthy people from sick people—but its neatness made it easy to teach and remember.
Normal temperature is a range, not a fixed point
A person’s temperature shifts over the day, often running lower in the morning and higher later on. It can also change with age, activity, hormones, and where the thermometer measures: an oral reading, for example, is not directly interchangeable with a reading taken in the ear or under the arm.
That variation means 98.6°F is not a reliable personal target. A healthy reading may be above or below it, and one reading alone cannot explain why someone feels unwell. Clinicians interpret temperature alongside symptoms, the person’s usual pattern, and the measurement method.
Why the old number can mislead
Researchers have reported that average body temperatures in some modern populations appear lower than the traditional benchmark. That does not mean everyone’s temperature has fallen by the same amount, or that a single replacement number now applies to all people. The practical point is simpler: normal is a range, and context matters more than matching 98.6°F exactly.
