Fertility Charting, basal body temperature (BBT), diabetes, basal body temperature (BBT) charting

What is a normal body temperature?

So you thought you knew what a normal body temperature is? Not so fast. Did you know that a normal body temperature depends on many factors, including:

  • a person’s age,
  • sex (male/female)
  • activity levels
  • for women whether they are pregnant or not
  • for non-pregnant women in which menstrual cycle stage they are: if they are before or after ovulation
  • body mass index
  • the time of the day, typically being lowest in the early morning and highest in the late afternoon
  • food and fluid intake
  • the method of measurement, such as highest rectal (bottom), then oral (mouth), ear, and lowest armpit readings
  • ethnicity

For many but not all people an average human body temperature is 98.6 °F (37 °C) orally. The normal range can be as low as 97.5 °F and as high as 98.8 °F (36.4 °C to 37.1 °C). The body temperature is considered dangerously low when it's below 95 F (35 C). There are some people with average temperatures in the 96 F range who are fine

Rectal temperatures:

0–2 years: 97.9–100.4°F (36.6–38°C)
3–10 years: 97.9–100.4°F (36.6–38°C)
11–65 years: 98.6–100.6°F (37.0–38.1°C)
Over 65 years:  97.1–99.2°F (36.2–37.3°C)

Ear temperatures:

0–2 years: 97.5–100.4°F (36.4–38°C)
3–10 years: 97.0–100.0°F (36.1–37.8°C)
11–65 years: 96.6–99.7°F (35.9–37.6°C)
Over 65 years: 96.4–99.5°F (35.8–37.5°C)

Oral temperatures:

0–2 years: 95.9–99.5°F (35.5–37.5°C)
3–10 years: 95.9–99.5°F (35.5–37.5°C)
11–65 years: 97.6–99.6°F (36.4–37.6°C)
Over 65 years: 96.4–98.5°F (35.8–36.9°C)

Armpit temperatures:

0–2 years: 94.5–99.1°F (34.7–37.3°C)
3–10 years: 96.6–98.0°F (35.9–36.7°C)
11–65 years: 95.3–98.4°F (35.2–36.9°C)
Over 65 years: 96.0–97.4°F (35.6–36.3°C)

Download this helpful graphic from Welch-Allyn

What is an elevated temperature? 

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. 

Reasons for a low temperature

The most common cause of a lower-than-normal body temperature is exposure to cold. But occasionally, low body temperature can indicate an underlying problem or condition, such as:

  • Inactivity
  • Underactive thyroid (hypothyroidism)
  • Diabetes
  • Adrenal gland insufficiency (Addison's disease)
  • Hypothalamus dysfunction
  • Liver failure
  • Kidney failure
  • Widespread infection (sepsis)
  • Excessive use of alcohol or illicit drugs
  • A side effect of certain medications, such as phenothiazines, barbiturates, opiates, clonidine, lithium, and benzodiazepines
  • Cold exposure
  • Alcohol consumption (see Alcohol use)
  • Hypoglycemia
  • Impaired shivering capacity in elderly
  • Myxoedema
  • Starvation
  • Malnutrition
  • Hypopituitarism
  • Exposure to cold outdoors
  • Immersion in cold water
  • Vasoconstriction failure
  • Kwashiorkor
  • Erythroderma
  • Paget's disease of bone
  • Uremia
  • Cerebrovascular injury (see Cerebrovascular symptoms)
  • Cerebral trauma
  • Diabetic ketoacidosis
  • Wernicke's encephalopathy
  • Carbon monoxide poisoning
  • Anoxic brain injury
  • Cardiac arrest
  • Organophosphate poisoning
  • Spinal cord lesion
  • Terminal malignant disease
  • Severe hepatic cirrhosis

If you have a low body temperature, especially if you are recognizing this as a new symptom, see your doctor.


Body temperatures

Read More:
Thyroid Disease and Pregnancy
Diagnosing Gestational Diabetes