Normal isn’t always normal.

Taking vital signs on a patient is done many times as part of the rhythm of a nurse’s day.

It is a skill that is taught early on in a nurse’s education.

What if the temperature that is considered normal is not “normal”.

The body temperature of a healthy human being is considered normal at 98.6 degrees Fahrenheit (F) or 37 degrees Centigrade (C).

In the mid 1800’s, Carl Wunderlich, a medical director at Leipzig University hospital, conducted a study on the vital signs of over 25,000 patients.

The study found that the average temperature of a normal human being was 98.6 degrees Fahrenheit (F) or 37 degrees Centigrade (C).

The thermometer that was used was subsequently found to have been two degrees Centigrade higher than it should have been.

Freakonomics Radio has put together part of a podcast about this thermometer in the episode called “Bad Medicine, Part 1: The Story of 98.6.”

The thermometer that Wunderlich used was a non-registering thermometer, which meant that it had to be read in place.

It was awkward to use.

It only measured axillary temperatures.

A modern temperature study in 1992 reviewed the work of Carl Wunderlich. 

It was entitled A Critical Appraisal of 98.6°F, the Upper Limit of the Normal Body Temperature, and Other Legacies of Carl Reinhold August Wunderlich by Philip Mackowiak, Steven Wasserman and Myron Levine.

It found that that only eight per cent of the 148 people studied had a temperature of 98.6F.

So if 98.6 was normal, this meant that 92 per cent were abnormal.

The study found that the actual normal temperature was 98.2F or 36.8 C, with an upper limit of 37.7C or 99.9F.

So one person’s normal could be considered a fever in another with the the variations that occur from person to person.

Temperature varied for a number of study participants.

There is a 6AM trough for temperature and a peak between 4-6PM.

Women who are ovulating have elevated temperatures.

There was a tendency for higher temperatures to be recorded among black than among white subjects.

The study concluded 

Thirty-seven degrees centigrade (98.6°F) should be abandoned as a concept relevant to clinical thermometry; 37.2°C (98.9°F) in the early morning and 37.7°C (99.9°F) overall should be regarded as the upper limit of the normal oral temperature range in healthy adults aged 40 years or younger, and several of Wunderlich’s other cherished dictums should be revised.

An increase in temperature is not a reliable sign of disease or infection.

To learn more about “normal” temperature: