What Is a Normal Body Temperature?

On average, the human body temperature is 98.6 degrees F. However, normal adult body temperatures range from 97 to 99. Your temperature can fluctuate and varies based on your age and the method used to measure your temperature. A fever is when your body temperature is higher than normal. Most healthcare providers consider a fever to be at 100.4 or higher.

This article reviews normal human body temperature and fever based on age, how it varies with measurement methods, symptoms and at-home fever treatment, and when to call a healthcare provider.

Is 98.6 Degrees a Normal Temperature?

The average human body temperature is 98.6. However, this is just an average and varies among people. Several factors can affect body temperature, including age, sex, and where on your body you take it. 

Your baseline daily temperature is a good reference point, and everyone's unique. For example, your daily average temperature could be around 97 degrees while your friend's average temperature is 98.7. Across a person's life span, healthy, normal body temperature ranges in degrees Fahrenheit are from 96 to 99.9 as follows: 

Infants and Children

A baby or child’s normal temperature varies based on age as follows:

• Preterm newborns: 97.7–98.6
• Term newborns: 97.2–99.9
• Babies less than 6 months old: 97.2–99.9
• 6–12 months: 96–99.4
• 1–13 years: 95.9–99

Adults 

The normal body temperature range for teens and adults is 97–99. People over age 60 have slightly lower temperatures than those younger than 60.

Average Temperature by Method

Body temperature differs based on where on your body you take your temperature. 

Central temperature measurement sites include the rectum (anus) or urine. They are the closest to your core (internal) temperature. But they can be invasive and are typically reserved for young infants or people who are severely ill.

Peripheral sites include oral (mouth), axillary (armpit), or tympanic (ear). Environmental temperature can influence these areas, so they are slightly less accurate than central sites. However, they are more accessible and practical for daily use. 

Oral

Oral temperatures are taken in the mouth. The room temperature, hot or cold liquids, and probe placement can influence oral temperatures. One study showed a variation of 3.6 degrees between oral and rectal temperatures. Normal and average oral temperatures are:

• Normal range: 96.3–99.3
• Average: 97.8

Tympanic

Tympanic (ear) thermometers are fast and easy to use. They can vary a couple of degrees between ears and in comparison to a rectal temperature. Normal and average tympanic temperatures are:

• Normal range: 96.4–99.5
• Average: 97.9

Axillary

Axillary temperatures are taken under the arm. They are affected by the external environment and vary from rectal temperatures. Normal and average axillary temperatures are:

• Normal range: 95.1–98.4
• Average: 96.7

Rectal

Rectal (in the anus) temperature most accurately measures the core temperature. They are typically about 1 degree higher than oral readings. Healthcare providers commonly use rectal temperature measurements for babies less than 3 months old. Normal and average rectal temperatures are:

• Normal range: 97.3–99.9
• Average: 98.6

What’s Considered a Fever?

A fever is when your body temperature is higher than normal and is usually a response to a disease or illness. Fevers are graded as mild, high, and very high as follows:

• Elevated body temperature: 99.5–100.4
• Low-grade fever: 100.4 or higher
• High-grade fever: 103
• Very high or dangerous: Above 105

The following is how a fever is defined in children based on where the temperature is taken:

• Rectal: Above 100.4 
• Oral: Above 99.5
• Axillary: Above 99 

Guidelines for seeking medical attention, based on age, are:

• 3 months or younger: Rectal temperature over 100.4 
• 3–12 months: 102.2 or higher
• 12 months to 2 years: 103 or higher, despite treatment or any fever that lasts longer than 24–48 hours
• 2 years and older: 103 or higher, despite treatment or any fever lasting longer than 48–72 hours

The following guidelines for seeking medical attention for a fever apply to any age, including adults:

• An elevated temperature that comes and goes for a week or more, even if it’s not considered a fever
• Other symptoms of illness, along with the fever
• People with any grade of fever who have had an organ transplant or a serious medical illness 
• Those who have recently traveled to another country

Low Body Temperatures 

While people often are concerned with elevated temperatures and fevers, it’s important to note that low body temperatures could signify a health condition, as well, especially in infants.

A low body temperature in infants could indicate a serious illness called meningitis. A rectal temperature is the most accurate for infants younger than 3 months old. 

Symptoms of Fever

Symptoms of a fever can be constant or intermittent (come and go). They include: 

• Feeling warm or hot 
• Skin warm to touch
• Flushed face
• Tired eyes
• Chills

If the following symptoms occur along with a fever, they could indicate an underlying health problem that requires medical attention:

• Malaise (generally feeling unwell), especially if occurring with a fever
• Decreased urine output or dark urine
• Persistent nausea or vomiting
• Persistent constipation or diarrhea
• Headache
• Aching
• Confusion
• Stiff neck
• Fever that has persisted for more than 48 hours

Regardless of their body temperature, the following signs and symptoms indicate an infant, child, or nonverbal adult should receive medical attention: 

• Behavioral changes (such as being less alert, not smiling, not playing, prolonged extreme fussiness or agitation)
• Decreased appetite or refusing food
• Abnormal skin color
• Decreased urine output
• Changes in bowel pattern
• Breathing difficulties
• Passing out
• Seizures

The following are safety considerations when treating a fever at home:

• Avoid giving medications to infants 3 months or younger before calling your child's provider.
• Do not use ibuprofen in children 6 months or younger.
• Do not give aspirin to a child unless your child's provider tells you to. It can cause a serious illness called Reye's syndrome.
• Avoid bundling with multiple blankets or jackets, even if you, another adult, or a child has the chills.
• Do not use cold baths, ice, or alcohol baths as they can cause shivering and increase core body temperature, which can be dangerous. Lukewarm baths are fine and helpful. 
• Avoid too much sugar when taking in fluids. 
• Do not force food on someone who is refusing it. 

Associated Factors in “Normal” Temperature Readings

As mentioned above, age, temperature measurement site, and the time of day factor into your normal body temperature. Sex also plays a role. People assigned female at birth tend to have higher temperatures. This also fluctuates during their menstrual cycle, ovulation, and pregnancy. 

Other factors include:

• Physical activity
• Stress or other strong emotions
• When you eat
• Heavy clothing or blankets
• Hot or humid environments 
• Health conditions, including hypothyroidism, autoimmune disorders, and some types of cancer
• Immunization (children may have a low-grade fever)
• Teething (elevated temperature, not usually get higher than 100) 
• Some medications

Summary 

The average human body temperature is 98.6 degrees F. Healthy, normal body temperatures range from 96 to 99.9 and vary across the life span. Several factors can affect body temperature, including age, sex, and where on your body you take it.

A body temperature over 100.4 is considered a low-grade fever, temperatures over 103 are a high-grade fever, and temperatures over 105 become more dangerous, especially if untreated.

A Word From Verywell 

Fevers occur when your body is fighting an infection. They often resolve in a few days. But, high-grade or prolonged fevers can indicate a serious underlying health problem. If you or your loved one has a high-grade or prolonged fever, notify your healthcare provider. Infants three months or younger with a rectal temperature over 100.4 should see a healthcare provider.