You've probably had it drilled into your head that your body temperature "should" be 98.6 degrees Fahrenheit and that anything higher or lower than that signals that's something is wrong. But that's not quite true.
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In general, normal body temperature differs among individuals and ranges from about 97 to 99 degrees Fahrenheit (36.1 to 37.2 degrees Celcius) when taken with an oral thermometer. But your normal body temperature varies depending on factors such as your age, gender, race and time of day, among others.
Here's the good news: A slightly lower-than-normal temperature is usually nothing to worry about. But a consistently or very low body temperature — less than 95 degrees Fahrenheit (35 degrees Celcius) — often signals accidental hypothermia or an underlying medical issue. Here are several of the possible causes along with when to see your doctor.
1. Exposure to Cold
Your body temperature reflects the balance between the heat your body generates versus how much it loses. Prolonged exposure to a cold environment can potentially lead to hypothermia because of excessive heat loss. Infants and seniors are particularly susceptible to hypothermia, as their bodies don't regulate body temperature as well as those in other age groups.
Serious hypothermia is more likely to occur in extreme conditions — such as if your car breaks down in a blizzard — than if you spend a few hours bundled up at a football game on a cold day. If you plan to spend time outside in cool or cold weather, dress in warm clothing and avoid drinking alcohol, as it dilates your superficial blood vessels and increases loss of body heat.
Read more: 10 Cold Weather Injuries and How to Stay Safe
2. Hormonal Conditions
A variety of hormonal disorders can lead to a low body temperature. Your thyroid, pituitary gland and adrenal glands make important hormones that regulate many bodily functions, including maintenance of your body temperature.
Reduced production of hormones from any of these glands can potentially lead to a lower-than-normal body temperature. In fact, a low body temperature sometimes serves as an important clue to a hormonal problem.
Hypothermia also poses a risk for people with diabetes mellitus. Complications of diabetes — including low blood sugar (hypoglycemia or an insulin reaction) and metabolic derangements due to a very high blood sugar level (diabetic ketoacidosis or hyperosmolar hyperglycemic nonketotic syndrome) — often cause a drop in body temperature along with other signs and symptoms.
3. Nervous System Disorders
An area of your brain called the hypothalamus serves as the primary site of body temperature regulation. It sends messages to the rest of your body that result in either overall heat conservation or loss.
Nervous system disorders can disrupt this temperature regulation, leading to a low body temperature. Examples of these disorders include:
Read more: 4 Weird Ways Your Body Warns You Something Is Wrong
Most people think a fever and infection go hand in hand — and they usually do. But a serious infection like bacterial pneumonia or meningitis sometimes triggers a low body temperature, especially among infants and aging seniors.
Hypothermia associated with a serious infection often indicates a complication called sepsis, which refers to an out-of-control inflammatory response to the infection leading to malfunction of body organs or systems. The development of a low body temperature in the face of sepsis typically signals a potentially life-threatening situation, as found in a study reported in October 2016 in the journal Critical Care.
5. Other Causes
A slight decrease in body temperature is a potential side effect of certain medications, including some types of drugs used to treat insomnia, anxiety, depression and other serious mental health challenges. A medication-related decrease in body temperature usually doesn't pose a threat to your overall health.
Additional possible, uncommon causes of low body temperature include:
Read more: 11 Warning Signs Your Skin Is Sending You
When to See a Doctor
While it's important to monitor your vital signs and make sure they're within normal limits, you don't need to run to the doctor every time your body temperature raises or lowers a degree or two. As mentioned earlier, a temperature as low as 97 degrees Fahrenheit (36 degrees Celicius) can be perfectly normal if you otherwise feel well.
But you should see your doctor if your body temperature is regularly less than 97 degrees Fahrenheit, especially if you experience other signs or symptoms.
Contact your doctor right away if you have an infant with a rectal temperature less than 97.7 degrees Fahrenheit (36.5 degrees Celcius). If you cannot reach your baby's doctor, take your child to the nearest urgent care clinic or emergency room.
Call 9-1-1 for emergency medical care if any warning signs or symptoms indicating possible hypothermia occur, including:
- Mental confusion, irrational thinking, agitation or decreased consciousness
- Slurred speech
- Poor coordination that resembles alcohol intoxication
- Rapid heart and/or breathing rate
- Persistent shivering
- Cool, pale or mottled skin
Is This an Emergency?
- Merck Manual Professional Version: Hypothermia
- JAMA: The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3)
- Critical Care: Risk Factors, Host Response and Outcome of Hypothermic Sepsis
- American Family Physician: Diagnosis and Treatment of Hypothermia
- Merck Manual Professional Version: Hypothermia in Neonates
- BMJ: Individual Differences in Normal Body Temperature: Longitudinal Big Data Analysis of Patient Records