Normal Body Temperature is Not 98.6 Degrees Fahrenheit

Joseph R. Anticaglia, MD
Medical Advisory Board

Physicians know to treat the patient, not the Xray or the thermometer. Mitchell, a 34 year-old CPA, complained over the past two days of coughing, difficulty swallowing, having a severe sore throat and “running a high temperature.”

Examination: His throat was slightly red with yellow mucus dripping down the back of his throat. There were swollen glands (cervical adenopathy) on both sides of the neck. His temperature was 97.2 degrees Fahrenheit.

“You don’t seem to have a temperature.”

“Doc, I run a low, normal temperature. I’m sick. If I don’t get treated with an antibiotic, I’ll be going from bad to miserable.”

A culture and sensitivity of the throat was done which proved Mitchell knows his own body, He had a bacterial infection and was treated with an appropriate antibiotic.

Sick patients with low body temperature readings have received renewed interest over the past few years. Studies suggest that 98.6 degrees Fahrenheit is not the average normal body temperature in the US.

Who Said 98.6 F is Normal?

In 1851, the German physician Carl R. A. Wunderlich measured the axillary (armpit) temperatures of 25,000 people in Leipzig. He published his findings in a book in which he concluded that the average human body temperature was 98.6 degrees Fahrenheit; and 100.4 F, or above, indicates a person has a fever. For over 150 years, the vast majority of doctors and people have accepted Wunderlich’s findings as a valid standard. However, modern studies question the validity of his conclusions.

Modern Studies

“Core” or average or normal body temperature refers to the temperature in the interior of the body. A Stanford University, School of Medicine study determined that the human body temperature in the United States for men and women has been decreasing at a rate of 0.05 degrees Fahrenheit every decade since the 19th century. Stanford University’s report corroborate the work of other researchers, which determined the body temperature is lower than that estimated by Wunderlich.

Metabolism and Lower Body Temperature

Your metabolic rate is an important determinant of your body’s temperature. Metabolism uses chemical reactions in your body to change food into energy and during this process it generates heat. It’s postulated that the lower metabolic rate in the modern era generates less energy needed by the body to function normally. As a consequence, the body produces less heat resulting in a lower body temperature.

The hypothalamus is a part of the brain that acts as the body’s thermostat. It’s responsible for maintaining the body’s temperature within a certain range, so that the body’s chemical reactions proceed smoothly.

Core Temperature is “Personal”

The Stanford study found that the core body temperature is “personal” — it varies from person to person due to several factors which include:

Time of day — the temperature varies during the day — being lower in the early morning and higher in the afternoon.

Age — Temperatures decrease with age. Younger persons tend to have higher temperatures than older people.

Sex — men tend to have lower temperatures than women.

Height and Weight — temperature increases slightly with weight and decreases slightly with height.

Other Factors not included in the Stanford study which could influence core body temperatures include weather, physical activity, hormones, and clothing.

Body Temperature Matters

Body temperature is one of the vital signs routinely checked by your doctor along with blood pressure, heart rate, and respiratory rate. The body performs trillions of chemical reactions every day. It requires internal temperature stability with minimal variation to function optimally. The hypothalamus works to stabilize the body’s internal temperature.

Abnormal vital signs are red flags for physicians to dig deeper to uncover their causes. An elevated temperature can mask bacterial infections that can damage the heart, kidneys or other organs. The accurate diagnosis and treatment of a person’s condition with a fever can prevent serious complications.

How Do You Define Fever?

A fever is one vital sign that often forces a person to visit his or her doctor. It also compels the physician to understand the cause of the temperature elevation to treat it properly.

Today, in line with Wunderlich’s conclusions, the CDC “considers a person to have a fever when he or she has a measured temperature of 100.4° F (38° C) or greater, or feels warm to the touch.” In addition, it’s accepted that normal temperature is 98.6 degrees Fahrenheit. But is now the time to redefine normal temperature and fever?

Modern studies suggest that the normal temperature number is closer to 97.5 degrees Fahrenheit, and it varies among individuals. More research is needed to tell us about the significance of the downward, core temperature shift and treatment implications. In the meantime, it makes sense to listen to people like Mitchell.


  1. Nina Bai; Normal Body Temperature is Personal; Stanford University News Center; September 5, 2023
  2. Myroslava Protsiv, et al; Decreasing human body temperature in the United States since the Industrial Revolution; Stanford University, School of Medicine; eLife , Jan 7, 2020
  3. Wunderlich CA; Sequin E (1871) Medical Thermometry, and Human Temperature
  4. Carrie Macmillian; Is 98.6 Degrees Really a ‘Normal’ Temperature? Yale Medicine, July 30, 2020
  5. Ziad Obermeyer et al. Individual differences in normal body temperature: longitudinal big data analysis of patient records; BMJ, Christmas, 2017


Hypothermia — low body temperature; temperature less than 82,4 degrees Fahrenheit

Hyperthermia — high body temperature; temperature greater than 105 degrees Fahrenheit

Standford University — “Although there are many factors that influence resting metabolic rate, change in the population level of inflammation seems the most plausible explanation for the observed decrease in temperature over time.”

This article is intended solely as a learning experience. Please consult your physician for diagnostic and treatment options.