What is Normal Body Temperature? The Range, Causes of Abnormal Temps, and More

Your body temperature is a key vital sign of your overall health. Knowing the normal body temperature range and recognizing when you have a fever, low temperature or other abnormal reading is important. This comprehensive guide will examine the average normal body temperatures for oral, rectal, and other measurement methods, what causes abnormal high or low body temperatures, and key facts everyone should know about their body’s internal thermostat.

Key Takeaways:

  • The average normal body temperature is generally considered 98.6°F (37°C) taken orally.
  • Normal body temperature has a range of 97°F (36.1°C) to 99°F (37.2°C).
  • Factors like age, gender, time of day, ovulation, and where on the body it is measured impact normal temps.
  • Oral temperatures are 0.5-1°F lower than rectal and ear temps. Armpit temps run lower.
  • Fever is indicated by a body temperature of 100.4°F (38°C) or higher.
  • Low body temperatures under 95°F (35°C) may indicate hypothermia, drug overdoses, or disorders.
  • Causes of abnormal body temperatures include infection, inflammation, hormone levels, weather, medications, thyroid dysfunction, age, menstruation, pregnancy, and more.

Having an accurate understanding of healthy body temperature ranges provides a crucial benchmark for identifying concerning changes in your health early on. Monitoring for spikes, dips, and patterns outside of your normal can prompt you to seek medical care when needed. This guide outlines all the key facts and considerations regarding normal human body temperature ranges.

What is Considered a Normal Body Temperature?

Normal body temperature is not a single fixed number but rather a temperature range that varies by individual, measurement method, time of day, and other factors. The baseline temperature considered normal for adult men and women taken orally is 98.6°F (37°C). However, the “normal” temperature range spans from 97°F (36.1°C) to 99°F (37.2°C).

Rectal temperatures, often taken for infants or young children, are typically 0.5 to 1°F higher than oral readings. Ear or temporal artery temperatures are generally as accurate as oral temperatures. Armpit or axillary temperatures tend to run lower.

So while 98.6°F (37°C) is a useful benchmark, it does not necessarily indicate an exact “normal” temperature for every person in every scenario. The key is tracking your personal average temperature and range day to day for your specific measurement method. Recognizing personal variations as well as factors that influence body temperature provides the most accurate sense of your own normal.

Average Normal Temperature Ranges

Here is an overview of the average normal temperature ranges by site:

  • Oral: 97°F to 99°F (36.1°C to 37.2°C), with an average of 98.6°F (37°C)
  • Rectal: 97.5°F to 99.5°F (36.4°C to 37.5°C), 0.5 to 1°F higher than oral
  • Ear (tympanic): 97.5°F to 99.5°F (36.4°C to 37.5°C), similar to oral
  • Forehead (temporal artery): 97.5°F to 99.5°F (36.4°C to 37.5°C)
  • Armpit (axillary): 96.5°F to 98.5°F (35.8°C to 36.9°C), 0.5 to 1°F lower than oral
  • Groin: 97°F to 99°F (36.1°C to 37.2°C)
  • Finger: Slightly lower than oral, not considered highly accurate

So generally, oral and ear/temporal temps align; rectal is slightly higher, and armpit is slightly lower than the average oral reading. Tracking your personal average range with one consistent method provides the best gauge.

Key Factors That Impact Normal Body Temperature

A variety of factors impact an individual’s normal body temperature range including:


  • Infants tend to run slightly warmer, around 99°F (37.2°C) on average. Elderly adults may run cooler temperatures.


  • Women generally run slightly higher body temperatures than men, especially around ovulation during the menstrual cycle.

Time of Day

  • Body temperature fluctuates throughout the day, typically peaking in the late afternoon and evening and hitting a low during nighttime sleep. A typical fluctuation is 1°F across the day.

External Conditions

  • Hot or cold weather and environmental temperatures can impact internal body temperature. Exercise, sun exposure, and overheated indoor spaces also raise body heat.


  • Metabolism, energy expenditure, and muscle mass influence the body’s thermoregulation and ability to stay cool. Higher metabolism and activity levels tend to increase body heat.


  • Hormone levels during the menstrual cycle, pregnancy, and menopause impact normal body temperature. Ovulation, in particular, causes a slight uptick in basal body temp used to track fertility.


  • Certain drugs including hormones, steroids, some antidepressants, and heart medications can impact body temperature regulation.

Circadian Rhythm

  • The body’s internal clock linked to sleep/wake cycles causes natural fluctuations in temperature through the day.

Immune Activity

  • When fighting an infection or illness, the immune system raises body temperature to activate defenses, indicated by a fever.

So while the average normal temperature is 98.6°F (37°C), each person’s healthy baseline temperature and range varies. Tracking your personal normal patterns provides the most accurate point of comparison.

How to Take an Accurate Body Temperature

To get an accurate reading of body temperature, it’s important to use proper technique for the measurement method. Steps for taking an accurate oral temperature include:

  • Use a digital thermometer, cleaned with alcohol before each use, for most accurate readings. Glass mercury thermometers can be used if properly sanitized.
  • Wait at least 15-20 minutes after eating, drinking anything hot or cold, exercising, or bathing before taking your temperature. This allows your mouth to return to its normal baseline temperature.
  • Keep the thermometer in place with your lips closed while measuring. Breathe through your nose.
  • Place the thermometer tip under your tongue close to the rear sublingual pocket.
  • Hold in place for the minimum time recommended by the manufacturer, usually around 30-60 seconds, until you hear the “beep” indicating it’s done.
  • Read your temperature to the nearest tenth decimal if using a digital thermometer.
  • Note the time of day for tracking patterns. Morning temperature will run lower than later day readings.
  • Record your reading to begin tracking your average normal range.

For rectal use, carefully follow directions to insert about 1/2 to 1 inch into the anus, using petroleum jelly, and hold for time indicated. Armpit temperatures should be taken mid-armpit with arm held against the body. Ear thermometers must be properly placed at the ear canal opening; swipe across the forehead for temporal readings.

Taking your temperature at regular daily intervals helps determine normal patterns. Comparing temperatures at the same time of day – morning, afternoon, evening – gives the most useful data. Keeping a record also helps identify body temperature changes possibly indicating illness.

What is Considered a Fever?

A fever indicates that body temperature is elevated above the normal range due to your immune system and inflammation responses activated to fight infection or illness. Most medical authorities define a fever as:

  • Lower-end fever: 100.4°F (38°C)
  • Mild or low-grade fever: 100.4°F to 102.2°F (38°C to 39°C)
  • High fever: 103°F (39.4°C) or higher

A temperature above 100.4°F (38°C) signals your body is ramping up immune activity to combat infection or inflammation. Sustained high fevers above 104°F (40°C) are of greater concern, especially in infants. Fevers themselves are not dangerous, but the underlying cause needs to be diagnosed.

Seek medical care for any fever in infants under 3 months, high fevers not responding to treatment in children, or fevers over 101°F (38.3°C) lasting more than 3 days in adults. Monitor symptoms and follow treatment guidelines while your body fights infection.

What Causes Abnormal High or Low Body Temperatures?

Both abnormally high and low internal body temperatures can result from a wide range of medical conditions and environmental factors. Here are some common causes:

Fever Causes

  • Infection: Viruses, bacteria, and other invading pathogens trigger immune responses and inflammation. Common examples include respiratory infections like influenza, pneumonia, COVID-19, strep throat; UTIs, stomach bugs.
  • Inflammation: Arthritis, autoimmune disease, inflammatory bowel disease.
  • Medications: Antibiotics, antimalarials, drug hypersensitivities.
  • Heat stroke: Extreme heat exposure causes dangerously high body temperature over 104°F (40°C). Requires emergency treatment.
  • Cancer: Leukemia and lymphoma can raise temperatures.
  • Hormone disorders: Thyroid storm, adrenal crisis.
  • Immune disorders: Lupus, rheumatoid arthritis, graft-versus-host disease.

Low Body Temperature Causes

  • Hypothermia: Exposure to cold weather, water; heat loss from inadequate clothing, shelter. Requires emergency rewarming.
  • Sepsis: Body’s extreme response to severe infection depresses temperature.
  • Alcohol or drug intoxication
  • Anesthesia side effects
  • Hormone disorders: Hypothyroidism, pituitary gland dysfunction, adrenal insufficiency.
  • Malnutrition, eating disorders
  • Diabetes mellitus
  • Nervous system disorders: Spinal cord injury, Guillain-Barre syndrome, stroke.

If body temperature abnormalities cannot be explained by a short-term or minor illness, see a doctor to determine if an underlying medical condition requires treatment. Let your doctor know if you have any symptoms accompanying abnormal body temperatures.

3 Key Points to Know About Body Temperature:

  1. Take temperature accurately: Use proper technique for the method; track changes at same time of day.
  2. Know your healthy normal: Record readings to determine your average and range.
  3. Identify concerning shifts: Fevers over 100.4°F (38°C), low temps under 96°F (35.6°C) need evaluation.

Following these guidelines provides a vital benchmark for monitoring your health and detecting when something may be wrong. While the average normal body temp is 98.6°F (37°C), your personal normal range may differ. Tracking patterns, ranges, and meaningful changes empowers you to recognize potential illnesses early. Consult a doctor to determine causes and treatment anytime temperatures deviate from what’s normal for you.

Frequently Asked Questions About Body Temperature

Here are answers to some common questions people have about normal body temperature readings and what impacts them:

What is the normal body temperature for a baby?

The average normal body temperature for babies and children under age 3 is slightly higher than adults, around 99°F (37.2°C) versus 98.6°F (37°C). However the normal range spans 97.9°F (37.2°C) to 100.4°F (38°C). Check with your pediatrician for their precise temperature guidelines.

Does normal body temperature change with age?

Yes, body temperature norms vary by age. Newborns up to 3 months may run as high as 100.4°F (38°C). Children age 3 and above align more closely with adult averages. Elderly people tend to run cooler temperatures.

Is body temperature higher during ovulation?

A woman’s body temperature may increase 0.5°F to 1°F during ovulation as part of the normal menstrual cycle. Tracking basal body temperature is used as a fertility indicator to identify when ovulation occurs.

Does normal body temperature vary by gender?

Yes, studies show that adult females generally have slightly higher average temperatures than males by about 0.5°F. This may relate to hormonal differences. Core body temperature does not vary much between sexes.

Why are oral and rectal temperatures different?

Rectal temperatures taken properly read 0.5°F to 1° higher than oral, because the internal body cavity is warmer than the mouth. Doctors may take rectal temps for accuracy in infants, when oral reading is questionable, or to check for temperature gradients indicating infection.

Following the guidelines provided in this comprehensive guide will help you understand the range for normal body temperature, how your individual norms may differ from average, and when abnormal high or low readings warrant medical evaluation. Monitoring patterns provides an important vital sign of your health status. Consult a doctor anytime your temperatures deviate from your normal in concerning ways.

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