Temperature is one of the four main vital signs that healthcare professionals consistently monitor. It’s “vital” because body core temperature changes can indicate a serious issue. Our very existence relies on the homeostatic process of internal body temperature regulation, also known as thermoregulation. (8) Continue reading to learn more about internal temperature levels and how to regulate body temperature through diet and lifestyle.

What are body temperature levels?

This refers to the measure of how efficiently the body generates and gets rid of heat. (2) Internal temperatures can either be normal, high, or low.

What is thermoregulation?

Thermoregulation is a mechanism that allows your body to maintain core internal temperatures with controlled self-regulation. The purpose of thermoregulation is to return your body to a state of homeostasis and equilibrium.

What regulates body temperature?

Human body temperature is regulated by a complex internal system that balances heat loss with body heat production and is dictated by the hypothalamus in the brain. The hypothalamus is like the body’s internal thermostat, making continual adjustments to keep the body at a normal temperature of 98.6 degrees Fahrenheit (37 degrees Celsius). If the body temperature is too low, the hypothalamus makes sure that the body generates more heat to maintain a normal temperature. A variety of other body organs and components including the skin, sweat glands, blood vessels, and hormones influence this internal thermostat. (2)

Body temperature levels

Body temperature can vary from low, normal to high. Typically, high internal temperature begins at about 100 degrees Fahrenheit (37.8 degrees Celsius). If temperature is consistently below 98.6 degrees Fahrenheit (37 degrees Celsius), it could indicate low temperature and should be evaluated. (1)(10) Before we dig into high and low temperatures, let’s take a closer look at what’s considered normal.

Normal body temperature

In the case of body temperature, “normal” may be a misnomer. In fact, we are now learning that temperature is highly individualized and can be influenced by many factors, including age, sex, circadian rhythm, metabolism, ovulatory cycles, and hormonal balance. “These factors vary dramatically across individuals, raising the possibility that individuals have baseline temperatures that differ systematically from the population average,” wrote the researchers of a 2019 cohort study published in the British Medical Journal. “The same temperature that is normal for one person might be dangerously high for another.” (7)

This type of debate about normal temperature continues in the medical literature and yet it’s also widely accepted that “normal” temperature is 98.6 degrees Fahrenheit (37 degrees Celsius). When dealing with body temperature, it’s important to address this debate. For example, according to a 2019 systematic review published in the journal Open Forum Infectious Diseases, the normal body temperature range should be 97.9 degrees Fahrenheit to 98.6 degrees Fahrenheit (36.6 degrees Celsius to 37 degrees Celsius). (3) This is consistent with other reports indicating that normal body temperature can be lower than 98.6 degrees Fahrenheit (37 degrees Celsius).

Jonathan Hausmann, MD, with the Boston Children’s Hospital and Beth Israel Deaconess Medical Center led a study to help redefine normal body temperature as it relates to fever. (5) “The assumption is that normal temperature is 98.6 degrees and fever begins at 100.4 . But we found the average temperature is more like 97.7 , and by defining ‘fever’ as temperature above the 99th percentile of normal, we found fever typically begins at about 99.5 degrees .” (5)

High body temperature

When a person has a fever, their temperature rises. This typically occurs when the body is fighting an infection or has an illness. A fever or elevated temperature may also be drug-induced, occur following a brain injury, or if the individual has an overactive thyroid (e.g., hyperthyroidism). (11)

Low body temperature

Conversely, low temperature could be a sign of an underactive thyroid (e.g., hypothyroidism). However, a person’s temperature is just one of several diagnostic factors related to hypothyroidism. (11)

What else causes low body temperature? Hypothermia, which is when the body temperature drops to dangerously low levels after being out in the cold for an extended period of time, is another example. Sepsis, a very serious and potentially deadly infection, may also cause body temperatures to drop below normal levels. (11)

Clinicians should establish a baseline normal for each of their patients and then monitor each patient accordingly.

How to promote body temperature regulation through diet and lifestyle

The three diet and lifestyle tips below may help raise, lower, or balance body temperature.

1. Eat thermogenic foods

Consuming thermogenic foods like hot red peppers and green tea may increase your temperature. Thermogenic means to produce energy, and in this case, thermogenic foods may increase metabolic rate, the amount of calories the body burns. (9)

2. Engage in regular physical activity

Physical exercise, especially in warmer temperatures, can increase internal temperature. Exercise also encourages blood flow and sweating, which help cool and regulate body temperature. (6)

3. Get enough quality sleep

Sound sleep may help balance your temperature, as well as many other body systems. (4)

The bottom line

Body temperature regulation can be unique to an individual’s physiology, age, sex, and other factors. Once a baseline range is established, monitoring an individual’s temperature remains vital. Both ends of the low-to-high temperature spectrum can present serious health issues that must be addressed clinically.