Outside temperatures can fluctuate constantly, but things work differently in your body. It craves a steady core body temperature, something stable and warm so your body runs properly. Core temperature changes a bit throughout the day, but big swings can spell trouble.
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What Is Core Body Temperature?
Your core body temperature is a measurement of your internal temperature using a thermometer in your ear, mouth, armpit, or rectum or on your forehead, according to the University of Michigan.
And that means actual core body temperature is different from our "feelings," Christopher Minson, PhD, a researcher and professor of human physiology at the University of Oregon, Eugene, tells LIVESTRONG.com. "Why people feel 'hot' or 'cold' at the same temperature is all due to perception." Ultimately, he adds, "temperature differences between our 'core,' our skin and the environment" determine how we may feel.
"Normal" core temperature is usually within a few decimals of 98 degrees Fahrenheit (F), ranging from 97 to 99 F, according to the National Library of Medicine (NLM).
Temperatures above and below that normal range can signal health concerns:
- Temperatures above 100.4 F indicate a fever, usually from illness.
- Temperatures at or above 104 F point to heat stroke, a life-threatening condition, notes the American Academy of Family Physicians.
- Hypothermia refers to an equally dangerous change when your temperature dips below 95 F, according to the NLM.
Though 98.6 F has been long considered the core body temperature standard, a December 2017 British Medical Journal study found that the average temperature across a group of 35,488 people was closer to 97.9 F.
There's also variation among individuals and devices used. An April 2019 study in Open Forum Infectious Diseases reported that the rectum or ear tend to yield higher measurements than the armpit or mouth. Younger people also tend to have slightly higher core body temperatures than older individuals.
Increasing Your Core Temp
Health experts at the University of Michigan note that your body constantly adjusts to keep your inner temperature consistent. In cold weather, for example, you shiver if you aren't warm.
The hypothalamus, a small region at the base of the brain, makes all this possible, according to Arizona State University. It compares your current temperature to your norm, sending signals just like a thermostat to help your body adjust.
Because your body is already wired to maintain its norm, you really can't "control" it per se or increase your own core body temperature. You can, however, help your body respond better to external factors.
Try these ways to warm up:
Dress appropriately for the weather, and in layers, according to Outdoor Action at Princeton University. Avoid damp or wet clothing because moisture near the skin cools you down. A hat is also a great accessory because lots of heat is released from your head.
Eat a Balanced Diet
More and stronger research is needed, but an October 2016 review in Nutrients suggests eating higher-calorie meals (and possibly those with protein and carbs rather than fats) may increase your core temperature slightly.
Try a Sauna or Steam
Some people enjoy a hot shower or sauna visit to stay warm, and the sweating is a help to keeping your temp in check. It's best to use these in 10- to 15-minute intervals, according to Harvard Health Publishing. Avoid them if you're pregnant, younger than 16 or sick.
Talk to Your Doctor
If you consistently feel too cold, talk to your doctor. You may have a condition that impacts temperature regulation or your body's ability to maintain heat in hands, fingers and toes, notes the Cleveland Clinic.
Cooling Down Your Core Temp
It's important to be careful when your aim is to lower your temperature, warns the American Academy of Family Physicians. After exercise in particular, your body temperature can be high and your heart may still be working overtime, per the American Heart Association. The cooldown period allows your body to adjust.
To avoid complications from heat, drink plenty of fluids and don't exercise or engage in extreme activity when heat and humidity are high (such as afternoons). At those times, shade is your friend. If your temperature moves outside the normal range for a prolonged period or reaches 104 F or higher, consult a doctor or call 911 immediately.
- University of Michigan: “Body Temperature”
- Christopher Minson, PhD, Kenneth M. and Kenda H. Singer Professor of Human Physiology, University of Oregon, Eugene
- National Library of Medicine: “Body Temperature Norms”
- American Academy of Family Physicians: “Heat Exhaustion and Heatstroke”
- U.S. National Library of Medicine: “Hypothermia”
- British Medical Journal: “Individual Differences in Normal Body Temperature: Longitudinal Big Data Analysis of Patient Records”
- Open Forum Infectious Diseases: “Normal Body Temperature: A Systematic Review”
- Arizona State University: “Ask a Biologist: The Brain”
- Outdoor Action, Princeton University: “Outdoor Action Guide to Hypothermia and Cold Weather Injuries”
- Mayo Clinic: “Heat and Exercise: Keeping Cool in Hot Weather”
- Nutrients: “The Energy Content and Composition of Meals Consumed after an Overnight Fast and Their Effects on Diet Induced Thermogenesis: A Systematic Review, Meta-Analyses and Meta-Regressions”
- Harvard Medical School: “Sauna Health Benefits: Are Saunas Healthy or Harmful?”
- Cleveland Clinic: “My Hands and Feet Are Always Cold — Should I Worry?”
- American Heart Association: “Warm Up, Cool Down”