You may have heard that the “normal” body temperature is 98.6°F (37°C). But this number is only an average. Your body temperature may be slightly higher or lower.

A body temperature reading above or below the average doesn’t automatically mean you’re sick. Several factors can influence your body temperature, including your age, sex, time of day, and activity level.

Read on to learn more about healthy body temperature ranges for babies, kids, adults, and older adults.

Your body’s ability to regulate temperature changes as you get older.

People over the age of 64 generally have more trouble adjusting to sudden changes in temperature as quickly as younger people. In general, older people have more difficulty conserving heat. They’re also more likely to have lower body temperatures.

Below are average body temperatures based on age, according to a review of studies and older research:

AgeOralRectal/EarArmpit
0–12 months95.8–99.3°F
(36.7–37.3°C)
96.8–100.3°F
(37–37.9°C)
94.8–98.3°F
(36.4–37.3°C)
Children97.6–99.3°F
(36.4–37.4°C)
98.6–100.3°F
(37–37.9°C)
96.6–98.3°F
(35.9–36.83°C)
Adults96–98°F
(35.6–36.7°C)
97–99°F
(36.1–37.2°C)
95–97°F
(35–36.1°C)
Adults over age 6593–98.6°F
(33.9–37°C)

94–99.6°F
(34.4–37.6°C)
92–97.6°F
(33.3–36.4°C)

Identifying your normal range can make it easier to know when you have a fever.

Keep in mind that average body temperature varies from person to person. Your body temperature might be up to 1°F (0.6°C) higher or lower than the guidelines above.

There are four different ways to take your or a family member’s temperature. However, the reading can vary from one method to the next.

The chart below shows which method is recommended for each age group:

AgeRectalTemporal (forehead)OralTympanic (ear)
Under 3 monthsX
3–6 monthsXX
6 months–3 yearsXXX
4 years–teensXXX
AdultsXXX
Older adultsXXX

You may have had your temperature checked under your arm, in the armpit. This method isn’t as accurate and not recommended.

German doctor Carl Wunderlich identified the average body temperature of 98.6°F (37°C) during the 19th century. However, many studies have since determined that that isn’t always the case.

A 2019 study found that the average body temperature is 97.86°F (36.59°C). That’s a little lower than initially thought so many years ago.

However, it’s best to take this information with a grain of salt since no single number defines your average body temperature. Instead, it’s best to look at a temperature range that may be higher or lower than the average.

Here are some of the factors that affect body temperature:

  • Our bodies tend to warm up throughout the day.
  • Older adults have lower body temperatures since our ability to regulate body temperature lessens as we age.
  • Younger people have higher body temperatures.
  • The level of physical activity affects temperature because the more you move your body, the warmer your core body becomes.
  • Hotter and colder weather can also mirror your body temperature — it rises when in a warm environment and lowers in the cold.
  • Temperature readings from the armpit are lower than the thermometer read from the mouth.
  • Thermometer readings from the mouth are lower than if taken in the ear or rectum.
  • Hormone levels can affect body temperature.
  • Excess weight can also be associated with lower body temperatures.

A higher-than-normal thermometer reading can be a sign of a fever.

The American College of Critical Care Medicine identifies a temperature of 100.9°F (38.3°C) or higher as a fever. As mentioned previously, the exact reading is dependent upon a few factors. If your temperature’s elevated above the normal range described earlier in the article, you may have a fever.

In general, a reading that’s 2°F (1.1°C) above your normal temperature is usually a sign of a fever.

Fevers can be accompanied by other signs and symptoms, including:

Our bodies have a built-in temperature control system. This operation raises the body temperature in response to disease and infection that you can sometimes fight without any intervention. With time and rest, your body temperature will likely return to normal without treatment.

When should I call my doctor if I have a fever?

On many occasions, a fever will go away on its own without treatment. However, you’ll want to seek medical advice if you have a fever and any of the following:

With babies and younger children, it can be hard to know when to speak with a doctor. Call your pediatrician if:

  • your baby is less than 3 months old and has a fever.
  • your baby is between 3 months and 3 years old and has a temperature of 102°F (38.9°C).
  • your child is 3 years or older and has a temperature of 103°F (39.4°C).

Seek medical care if your baby or child has a fever and:

  • has difficulty breathing
  • struggles to drink liquids
  • is under 3 months old
  • has a temperature over 104°F (40°C)
  • is shivering for more than 30 minutes
  • is inconsolable, especially when touched or moved
  • is unable to move an arm or leg as normal
  • appears dehydrated by low urine amounts, dry mouth, and no tears with crying
  • has pain with urination
  • appears very ill

If you feel your child should be seen by a medical professional, then trust your gut and have them checked out.

Hypothermia is a serious condition that occurs when you lose too much body heat. For adults, a body temperature that dips below 95°F (35°C) is a sign of hypothermia.

Most people associate hypothermia with being outside in cold weather for long periods of time. But hypothermia can occur indoors, too.

Babies and older adults are more susceptible. For babies, hypothermia can occur when their body temperature is 97°F (36.1°C) or lower.

Hypothermia can also be a concern in a poorly heated house in winter or an air-conditioned room in summer.

Other signs and symptoms of hypothermia include:

See a doctor if you have a low body temperature with any of the symptoms above.

A fever isn’t usually a cause for concern. The fever goes away with a few days of rest most of the time.

However, seek treatment when your fever climbs too high, lasts too long, or is accompanied by more severe symptoms.

Your doctor will ask questions about your symptoms. They might perform or order tests to determine the cause of the fever. Treating the cause of the fever can help your body temperature return to normal.

On the other hand, a low body temperature can also cause concern. Hypothermia can be life threatening if left untreated. Seek medical assistance as soon as you notice signs of hypothermia.

Your doctor will use a standard clinical thermometer to diagnose hypothermia and check for physical signs. In addition, they may use a low-reading rectal thermometer if needed.

In some cases, your doctor may order a blood test to confirm the cause of your hypothermia or to check for infection.

In mild cases, hypothermia may be harder to diagnose but easier to treat. Heated blankets and warm fluids can restore heat. Other treatments include blood rewarming and warmed intravenous fluids for more severe cases.

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