Normal Body Temperature: Ranges and Variation Explained

Medically Reviewed By Debra Sullivan, Ph.D., MSN, R.N., CNE, COI
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Temperature is one of the primary ways to gauge a person’s wellness. This is because the body can react to many illnesses in ways that change body temperature. Understanding optimal or normal body temperature ranges is crucial to recognizing when they are out of range, which can indicate illness.

a woman is outside with her hands on her forehead
Thais Varela/Stocksy United

Along with blood pressure, heart rate, and respiratory rate, body temperature is one of the primary vital signs used when assessing a person’s wellness. 

To establish a degree of sickness, it is important to know the expected ranges of body temperature. Body temperature ranges fluctuate based on age, gender, the measurement site, the person’s activity level, and the room’s temperature or environment.

This article will explain the expected temperature ranges, how to measure temperature accurately, when to seek help, and more.

Typical body temperature ranges

Typical body temperature ranges by age are as follows:

AgeOral temperature rangesArmpit temperature ranges
Up to 1 year old95.8–99.3°F (36.7–37.3°C)94.8–98.3°F (36.4–37.3°C)
Children97.6–99.3°F (36.4–37.4°C)96.6–98.3°F (35.9–36.83°C)
Adults96–98°F (35.6–36.7°C)95–97°F (35–36.1°C)
Adults over 65 years old93–98.6°F (33.9–37°C)92–97.6°F (33.3–36.4°C)

On average, adults aged 65 or older have lower temperatures than younger adults. Females have slightly lower temperatures than males.

The most important factors when determining a normal temperature are the person’s age and the site used to check the temperature. 

Your internal body temperature is higher than your external body temperature. Therefore, the method for taking a temperature measurement might yield different results, depending on where you take the temperature.

High temperature and fever 

A high temperature or fever usually occurs as a result of your body trying to fight off an infection.

The temperature for a fever differs depending on the age of the individual. For infants under 2 months old, a fever is 100.4ºF (38ºC) or higher. For children older than this, a fever is 101.5ºF (38.6ºC) or higher.

Contact a doctor if a child’s temperature is 102.2ºF (39ºC) or higher.

Call your doctor immediately if your temperature is 103ºF (39.4ºC) or higher, or if the fever occurs alongside other persistent symptoms.

Other symptoms of fever

Some signs you may have a fever include:

Low temperature and hypothermia 

Hypothermia happens when your body is exposed to cold or wet weather and is unable to maintain its temperature.

If your body temperature drops down to 95ºF (35ºC) or lower, seek immediate medical attention.

There are three stages of hypothermia:

  • Mild hypothermia is a temperature of 95–89.6ºF (35–32ºC).
  • Moderate hypothermia is a temperature of 89.6–82.4°F (32–28ºC).
  • Severe hypothermia is a temperature of 82.4ºF (28ºC) or lower.

Other symptoms of hypothermia temperature

In addition to a low body temperature, symptoms of hypothermia can include:

Seek immediate medical help if you or somebody else displays symptoms of hypothermia.

Why does body temperature fluctuate?

Body temperature changes and fluctuations can happen for several reasons.

Age

The average temperature will rise from childhood to adulthood and then decrease again in an older adult. 

Older adults have a lower body temperature because their metabolic rates slow down. They cannot regulate their temperature as easily as before in response to room temperature or other environmental factors.

External temperature

Body temperature can fluctuate in response to external temperatures, such as the temperature of a room or the weather outside.

If you have been outside for a while, wait 15 minutes before checking your temperature.

Reaction to an infection

A fever is your body’s way of fighting off infection. The temperature reading for a fever will depend on the method of taking a temperature reading.

Hypothyroidism

An underactive thyroid reduces your metabolism. This can lead to a lower body temperature, making you feel more intolerant to the cold.

Certain medications

Some medications can affect your ability to thermoregulate, lowering the body’s internal temperature. These can include antipsychotic medications

Time of day 

The time of day can affect your temperature reading. For example, your temperature might be lower in the morning if you have slept in a cool room, while your temperature may be higher after a busy day.

Menstrual cycle

Your temperature might fluctuate due to where you are in your menstrual cycle. Temperature before ovulation is typically around 96–98°F (35.5–36.6°C). After ovulation, the average temperature is around 97–99ºF (36–37.2°C).

How do I take a body temperature reading?

You can take a body temperature reading in different ways, including orally, rectally, in the ear, and under the armpit.

Oral temperature 

Use a digital thermometer to take an oral, or by mouth, temperature. 

  1. Before taking a temperature, be sure the person has not consumed anything hot or cold recently. 
  2. Turn the thermometer on. 
  3. Place the thermometer under the person’s tongue and have them close their lips around it. They should not bite the thermometer. 
  4. The thermometer will beep when the temperature reading is ready.

The typical body temperature range for an oral temperature reading is 96.3–99.3ºF (35.7–37.4ºC).

The average oral temperature is 97.8ºF (36.6ºC). A temperature reading of 100ºF (37.8ºC) or higher with an oral thermometer indicates a fever.

Forehead temperature

You can take a temporal artery, or forehead, temperature on anyone of any age. Follow the instructions on your thermometer regarding where to place it for the best reading. 

A temperature reading of 100.4ºF (38ºC) or higher with a forehead thermometer indicates a fever.

Ear temperature

You can use an ear thermometer on anyone older than 6 months

If the person has been outside, wait for 15 minutes before taking a temperature with an ear thermometer. Follow the instructions on your ear thermometer for the best reading.

Pulling the ear back is the key to getting an accurate temperature on an ear thermometer. If the child is over 1 year old, pull the ear up and back before placing the thermometer into the ear canal. 

The optimal body temperature range for a tympanic, or ear, temperature reading is 96.4–99.5ºF (35.8–37.5ºC).

The average tympanic temperature reading is 98ºF (36.6ºC). A reading of 100.4ºF (38ºC) or higher with an ear thermometer indicates a fever.

Armpit temperature

An axillary, or armpit, temperature is the safest way of taking a child’s temperature if they are under 3 months old.

To take an armpit temperature reading: 

  1. Turn the thermometer on.
  2. Place the tip into the armpit.
  3. Press the arm down onto the side of the chest.
  4. Make sure the tip stays surrounded by skin until the thermometer beeps.

The typical body temperature range for axillary, or armpit, temperature is 95–98.5ºF (35–36.9ºC).

The average axillary, or armpit, temperature is 96.7ºF (36ºC). A reading of 99ºF (37.2ºC) or higher with an armpit temperature indicates a fever.

Rectal temperature

A rectal temperature is the most accurate way of taking a temperature.

Use a digital thermometer for taking rectal temperatures. 

  1. Turn the thermometer on.
  2. Hold the child still.
  3. Insert the thermometer into the rectum very gently about half an inch to 1 inch. You should not feel any resistance. If you do, stop. 
  4. Hold the thermometer in place until it beeps. 
  5. Always disinfect the thermometer before and after rectal use.

The typical body temperature range for rectal temperature is 97.4–99.9ºF (36.3–37.7ºC).

The average rectal temperature is 98.7ºF (37ºC). A reading of 100.4ºF (38ºC) or higher with the rectal method indicates a fever.

Summary

Normal body temperature fluctuates based upon factors such as age, weather, activity level, and thyroid function. You can expect a certain amount of fluctuation throughout the day.

A temperature that is too high or too low can lead to life threatening conditions. Contact a doctor if you or someone you know has symptoms of a fever or hypothermia.

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Medical Reviewer: Debra Sullivan, Ph.D., MSN, R.N., CNE, COI
Last Review Date: 2022 May 31
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