Everything You Need to Know About Normal Body Temperature Range

Ever since the pandemic, there’s been a great deal of attention on monitoring body temperature. This has led to a rise in non-contact temperature assessment devices. As an initial check at entry points, they help identify people who may have elevated temperatures.

So what should be on these devices?

An adult typically has a body temperature of 98.6°F or 37°C.

But did you know that normal body temperature can vary from person to person? Scientists have found that many factors can influence a person’s body temperature, such as age, sex, and activity level.

So what’s normal for one person can be slightly different for another.

An article published in Medical News Today explains the normal range of temperatures for people of different ages and the factors that affect body temperature.

provider holding a thermometer

What is the Normal Range for Body Temperature?

The average normal body temperature is 98.6°F (37°C). Studies show that the “normal” body temperature actually exists between a range, from 97°F (36.1°C) to 99°F (37.2°C).

While it’s common for readings to differ from person to person, the same person can have a different reading at various times throughout the day.

But generally speaking, if an adult has a body temperature of at least 100.4°F (38°C), it suggests that they have a fever. 

If it’s above 103.1°F (39.5°C), it’s considered a high fever. And any reading above 105.8°F (41°C) is a very high fever.

Reasons Why Normal Body Temperatures Can Differ

Researchers noted differences between people’s normal body temperatures. The study looked at nearly 35,500 people. They found that older adults had the lowest temperatures while African-American females had higher temperatures than white males.

Here are a few key reasons why body temperatures can be different.

The Method of Measurement 

There are multiple ways to measure body temperature:

  • Oral (mouth)
  • Rectal (bottom) 
  • Armpit
  • Ear

The reading will vary in each location. For example, rectal readings are higher than oral readings, while armpit readings are lower than oral readings.

Age

When taken orally, the normal body temperature for a child between the ages of 3 and 10 ranges from 95.9–99.5°F. This is slightly lower than people between the ages of 11 and 65 (97.6–99.6°F). A similar range was noted for adults over the age of 65 (96.4–98.5°F).

But for babies (newborn to 2 years), the normal body temperature can be slightly higher than adults.

They have a larger body surface area relative to body weight, and they are more metabolically active.

The average body temperature of a newborn is 99.5°F, while an infant’s normal range is from 97.9–100.4°F (rectal reading).

It can increase a little while teething.

Gender

Although men and women maintain an average internal body temperature of 98.6 degrees, a person’s gender can make a slight difference. 

Men typically have more muscle mass and thus generate more heat. But sometimes, women will have a different body temperature depending upon the stage in their monthly menstrual cycle.

The Time of Day

Usually, the body temperature is the lowest in the early morning and the highest in the late afternoon.

Activity Level

Exercise increases a person’s core body temperature. Similarly, air temperature and humidity can cause the body temperature to rise.

After Eating Food

Twenty to thirty minutes after eating a meal, you’ll notice a slight increase in body temperature. This is due to the rise in metabolic rate that facilitates digestion.

Medical Conditions

Certain medical conditions also influence a person’s body temperature. For instance, someone with hypothyroidism (a condition when the thyroid is underactive) tends to have lower body temperatures, while a cancer patient may have a higher temperature.

So What is a Fever?

A person can have a fever if the body temperature is above 100.4 F (38 C). A fever is the body’s own disease-fighting arsenal, helping to kill off many disease-producing organisms.

So infections are usually the reason behind fevers. However, if the body temperature rises above or falls below normal, the hypothalamus (a part of the brain that helps regulate the body temperature) takes charge.

Best Way to Take a Temperature

There are several types of thermometers. However, the ideal one to use depends on a person’s age.

For instance, it’s better to use a rectal thermometer for babies between the age of 0 to 3 months. But you can use a rectal, ear, or armpit thermometer for infants between 3 months to 3 years. Anyone 4 years and older can easily use an oral, ear, or armpit thermometer.

If a reading is unusually high or low, take another one 5 to 10 minutes later. Or use a different thermometer if you think the readings are not correct.

When Should I Visit a Doctor?

The answer to this question depends on the age of a person who has a fever. Consider the following:

Adults

A short-term illness with a temperature of 100.4–104°F should not be cause for concern in otherwise healthy adults. But if the temperature rises above 104°F or goes lower than 95° F, you need to contact your doctor, especially if there are other symptoms such as confusion, headaches, or shortness of breath. Temperatures over 105.8°F can lead to organ failure.

However, even a low-grade fever can be worrisome for someone with a pre-existing condition, such as heart or lung problems.

Children

Children between 3 months and 3 years old don’t always need medicine, especially if the fever is lower than 102°F. But you should consult a doctor if the child has other symptoms such as dehydration, vomiting, or diarrhea.

Infant

If a baby 3 months or younger has a rectal temperature of 100.4°F or more, you need to get medical attention right away. Even a slight fever could indicate a serious infection.

Over to You

Normal body temperature readings tend to vary within a range due to several factors. It can get influenced by the age, sex, physical activity, and health of a person. 

Anyone with an unusually high or low temperature should seek emergency medical attention.

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