Normal body temperatures vary depending on many factors, including a person's age, sex, and activity levels.

The normal body temperature for an adult is around 98.6°F (37°C), but every person's baseline body temperature is slightly different, and may consistently be a little higher or lower.

In this article, we discuss the normal ranges of temperature for adults, children, and babies. We also consider factors affecting body temperature, and when to call a doctor.

Body temperature readings vary depending on where on the body a person takes the measurements. Rectal readings are higher than oral readings, while armpit readings tend to be lower.

The table below gives the normal ranges of body temperature for adults and children according to a thermometer manufacturer:

Type of reading0–2 years3–10 years11–65 yearsOver 65 years
Oral95.9–99.5°F (35.5–37.5°C)95.9–99.5°F (35.5–37.5°C)97.6–99.6°F (36.4–37.6°C)96.4–98.5°F (35.8–36.9°C)
Rectal97.9–100.4°F (36.6–38°C)97.9–100.4°F (36.6–38°C)98.6–100.6°F (37.0–38.1°C)97.1–99.2°F (36.2–37.3°C)
Armpit94.5–99.1°F (34.7–37.3°C)96.6–98.0°F (35.9–36.7°C)95.3–98.4°F (35.2–36.9°C)96.0–97.4°F (35.6–36.3°C)
Ear97.5–100.4°F (36.4–38°C)97.0–100.0°F (36.1–37.8°C)96.6–99.7°F (35.9–37.6°C)96.4–99.5°F (35.8–37.5°C)

Normal body temperature readings will vary within these ranges depending on the following factors:

  • a person's age and sex
  • the time of day, typically being lowest in the early morning and highest in the late afternoon
  • high or low activity levels
  • food and fluid intake
  • for females, the stage in their monthly menstrual cycle
  • the method of measurement, such as oral (mouth), rectal (bottom), or armpit readings

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A body temperature over 100.4°F (38°C) in adults indicates a fever.

A normal adult body temperature, when taken orally, can range from 97.6–99.6°F, though different sources may give slightly different figures.

In adults, the following temperatures suggest that someone has a fever:

  • at least 100.4°F (38°C) is a fever
  • above 103.1°F (39.5°C) is a high fever
  • above 105.8°F (41°C) is a very high fever

Researchers have looked into the individual differences between people's normal body temperatures. A study looking at almost 35,500 people found that older adults had the lowest temperatures, and African-American women had higher temperatures than white men.

They also found that certain medical conditions can affect a person's body temperature. For example, people with an underactive thyroid (hypothyroidism) tended to have lower temperatures, while people with cancer had higher temperatures.

A normal body temperature for children aged 3–10 ranges from 95.9–99.5°F when taken orally.

Children tend to have similar body temperatures to adults.

Sometimes, babies and young children have higher body temperature ranges than adults for armpit and ear measurements.

A normal body temperature for infants aged 0–2 years ranges from 97.9–100.4°F when taken rectally. Body temperature may rise a little when a baby is teething.

The average body temperature of a newborn is 99.5°F.

A baby's temperature is higher because they have a larger body surface area relative to their body weight. Their bodies are also more metabolically active, which generates heat.

Babies' bodies do not regulate temperature as well as adults' bodies. They sweat less when it is warm, meaning that their bodies retain more heat. It may also be more difficult for them to cool them down during a fever.

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A high temperature is a common symptom of short-term illnesses.

A dangerous body temperature depends on a person's age:

Adults

A temperature of 100.4–104°F caused by short-term illnesses should not cause significant harm in otherwise healthy adults. However, a moderate fever can be more worrying for a person with existing heart or lung problems.

Call a doctor for temperatures above 104°F or lower than 95° F, especially if there are other warning signs, such as confusion, headaches, or shortness of breath. Temperatures of over 105.8°F can cause organ failure.

Doctors define hypothermia as a temperature dropping below 95°F. Hypothermia can be dangerous if not treated quickly.

Children

Children aged between 3 months and 3 years old who have a fever but a temperature of lower than 102°F do not always need medicine. Call your doctor if a child has a temperature of over 102.2°F, or has a lower temperature but is experiencing dehydration, vomiting, or diarrhea.

Babies

If an infant of 3 months or younger has a rectal temperature of 100.4°F or above, seek emergency medical attention. In very young babies, a slight fever can signal a serious infection.

There are many types of thermometers available, and the best method depends on a person's age:

AgeBest method
0 to 3 monthsRectal
3 months to 3 yearsRectal, ear, or armpit
4 to 5 yearsOral, rectal, ear, or armpit
5 years to adultOral, ear, or armpit

Follow the instructions on the thermometer package.

If a temperature reading is unusually high or low, take another reading after about 5 to 10 minutes. If someone is unsure the reading is correct, they can take another reading with a different thermometer.

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Shivering occurs to help warm the body up.

An area of the brain called the hypothalamus regulates body temperature. If body temperature rises above or dips below the 37°F mark, the hypothalamus kicks in to regulate the temperature.

If the body is too cold, the hypothalamus sends signals to make the body shiver, which warms the body up. If the body is too hot, it sends messages to begin sweating, which lets heat leave the body.

Infections cause most fevers. A fever develops as the body's natural way of reacting to and fighting infection.

Doctors consider a fever to be a body temperature that reaches or exceeds 100.4°F. Other symptoms include:

  • appetite loss
  • chills
  • a headache
  • irritability
  • muscle aches
  • shivering
  • sweating
  • weakness

The ideal body temperature in adults is around 98.6°F, but this varies based on age, sex, physical activity, and health. Body temperature changes throughout the day. A temperature of above 100.4°F signals a fever.

Babies may have higher body temperatures than adults, but even a slight fever in babies can signal a severe infection.

Temperature readings taken from different body parts give a range of body temperatures that doctors consider normal. Rectal readings are higher than oral readings, and armpit readings tend to be lower.

If a person has an unusually high or low temperature, they should seek medical attention immediately.