Why the classic 98.6 degrees Fahrenheit body temperature is likely a myth

Health · Published 29 September 2026 Swipe more like this →

In short: For generations, we have been taught that a healthy human body temperature is 98.6 degrees Fahrenheit. However, modern research suggests the average person today runs cooler than this 19th-century benchmark. Your temperature is not a fixed number, but a dynamic range that shifts throughout your life and your day.

The widely cited standard of 98.6 degrees Fahrenheit originated from research conducted in the mid-1800s. Contemporary studies indicate that the average internal temperature for adults is now closer to a range between 97.5 and 97.9 degrees Fahrenheit. Researchers hypothesize that this cooling trend across the population may stem from improved hygiene and a reduction in chronic inflammation, which has historically driven up baseline temperatures.

Rather than a static value, body temperature is a homeostatic variable regulated by the hypothalamus. This brain region triggers physiological responses—such as shivering to generate heat or sweating to cool down—to keep the core within a safe window. This range is not universal; it fluctuates based on age, sex, time of day, and activity levels. For instance, temperatures typically hit their lowest point in the early morning and peak during the late afternoon. Women also experience rhythmic shifts in basal temperature linked to the menstrual cycle, which are often suppressed by hormonal contraceptives.

Age is a significant factor in these fluctuations. Children often exhibit higher temperature ranges and are more prone to rapid fevers, while older adults tend to have lower average temperatures and less daily variability. Because the body’s ability to regulate heat can diminish with age, even a modest elevation in an elderly person can signal a serious underlying condition. Ultimately, while 97 to 99 degrees Fahrenheit is generally considered normal for adults, the most accurate readings are obtained internally, such as under the tongue, rather than through external skin measurements.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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