Research shows normal human body temps have dropped from 98.6

Normal human body temperature established more than 170 years ago

Research shows normal human body temperatures have dropped

The coronavirus pandemic has forced many of us to have our temperature checked far more often than we’re used to -- and many of you may have noticed that your temperature is not always the same.

So what is a normal body temperature?

The standard 98.6 degree Fahrenheit gauge for normal human body temperature was actually established more than 170 years ago by a German doctor, who made millions of measurements in tens of thousands of patients. Since then, a lot of factors may have contributed to the change in our body temperatures, but one thing is certain: Humans’ normal body temperatures have been decreasing.

First and foremost, temperature readings can vary significantly depending on where you measure your temperature. The armpit, ear, mouth, skin and rectum are all different and temperature readings can vary by a few degrees.

But research shows that overall body temperatures have been decreasing over time.

One analysis of several studies found that body temperatures have been dropping consistently over the past 170 years, with the new normal being closer to 97.5 degrees, when taken orally.

There are ordinary things that can cause our baseline body temperature to change throughout the day or within days:

  • Our temperatures rise in the afternoon,
  • Older adults are cooler than younger people,
  • Women are generally warmer than men,
  • Women’s temperatures change with their menstrual cycle, and
  • Heavier people are warmer than thin ones.

But even when all of that is taken into account, on average, we are running cooler than we did over 100 years ago.

The real question is: why?

The answer is an unsatisfying “we don’t know,” but there are several theories that attempt to explain this change.

It is possible that our metabolisms have slowed down because of lifestyle changes, like air conditioning and less active jobs.

Others think the change could be caused by lower overall rates of low grade infections and inflammation related to better medical treatments available today.

Regardless, the change in our body temperatures begs the question of whether or not we need to update our definition of a fever, which is generally considered to be 100.4 degrees Fahrenheit. We’ve been using the 100.4 metric to determine fevers for ages, even though our baseline temperatures appear to be lower than once thought.

Redefining a fever probably isn’t necessary -- just don’t be surprised next time you have your temperature taken and it is less than 98.6 degrees Fahrenheit.


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About the Author:

Dr. McGeorge can be seen on Local 4 News helping Metro Detroiters with health concerns when he isn't helping save lives in the emergency room at Henry Ford Hospital.