What Is Normal Body Temperature?

A normal body temperature is best described as a range. The standard range is generally considered to be between 97 and 99 degrees Fahrenheit. Each individual might be slightly below or above this range. Body temperature is regulated by the hypothalamus, located at the base of the brain.

Measuring Body Temperature

Mercury-filled glass thermometers used to be the norm for measuring body temperature, but due to mercury’s toxicity, healthcare professionals recommend using digital thermometers.

There are a few ways to take your temperature: oral, rectal, or axillary. The digital reading will vary slightly depending on which method you use. 

• A rectal temperature is taken by inserting a thermometer into the rectum. This method is typically used in children from infancy to 3 years of age. A rectal temperature below 100.4 degrees Fahrenheit is normal.
• Oral temperatures are taken by mouth. This method is common for adults and children 3 years and older, provided they can hold the thermometer securely under their tongue. An oral temperature below 100 degrees Fahrenheit is normal.
• The axillary method is taken under the armpit. However, the reading is not as accurate, so should be followed up with an oral or rectal reading if fever is suspected. An axillary temperature below 99 degrees Fahrenheit is normal.

Other methods include forehead (temporal artery) and ear (tympanic) thermometers.

Conditions Affecting Body Temperature

Health conditions, environmental factors, and biological processes can cause body temperature to fluctuate. For instance, hormone changes during the female menstrual cycle can cause body temperature to rise. But certain situations can cause temperature changes that can pose health risks.

They include:

• Fever: A body temperature of 100.4 degrees Fahrenheit or more is considered a fever. This increase is usually in response to harmful viruses or bacteria invading the body.
• Heatstroke: This occurs when environmental conditions are extremely hot or humid. Sweat does not evaporate as quickly off the skin, causing the body to overheat. Core body temperature can reach levels as high as 106 degrees Fahrenheit.
• Hyperthyroidism: This is a condition where your body releases too much thyroid hormone. This causes your metabolism to speed up and one of the symptoms is an increase in body temperature and perspiration.
• Hypothermia: This happens when your body temperature goes below 95 degrees Fahrenheit. Hypothermia is caused by prolonged exposure to cold temperatures.
• Hypothyroidism: This is a condition where your body produces too little thyroid hormone. Your metabolism slows down too much and it becomes difficult to stay warm. 

A Word From Verywell

It can be easy to get preoccupied with data readings and worry if a number is a sign that something is wrong with your health. But not only does a normal body temperature vary throughout the day and from person to person, it can change for a population over time.

A study published in 2020 has shown that the average body temperature in the United States has actually decreased since the Industrial Revolution. 

With the exception of specific health conditions, your core body temperature will remain stable and within the normal range. Even a fever is not usually cause for immediate concern. But if your temperature is 103 degrees Fahrenheit or higher, call your healthcare provider.