Pop quiz: what’s a normal body temperature for a human being?
If you’re like most people, you probably answered 98.6 degrees. It’s such a given that you’ve probably never even thought to question it.
But how did 98.6 degrees become the magic number for human body temperature? Is it accurate? Is it true that certain people run hot or cold? And does diabetes have any effect on body temperature?
First things first: our belief that a healthy human’s body temperature is 98.6 is largely due to the work of a 19th century German physician named Carl Wunderlich. Wunderlich claimed to have analyzed more than one million independent temperature readings from about 25,000 patients and concluded that the average temperature of a healthy adult was 98.6 degrees Fahrenheit (37 degrees Celsius). He published his findings in 1868, and 98.6 has been used as a baseline ever since.
But it turns out that Wunderlich was likely incorrect. He measured his participants’ temperatures under their arms (a location that’s since been shown to be less accurate than the mouth or rectum), and we now have digital thermometers that are much more precise than the ones he used in the 1800s. According to a 1992 study published in The Journal of the American Medical Association (in which researchers took people’s temperatures in their mouths using carefully calibrated digital thermometers), the mean body temperature of a healthy adult is closer to 98.2 degrees Fahrenheit, with 98.9 degrees Fahrenheit in the early morning and 99.9 degrees Fahrenheit overall, as the upper limit of the normal range.
Our temperatures can vary by the day, and as Wunderlich himself observed, they also fluctuate according to our circadian rhythms: body temperatures tend to peak in the late afternoon, and reach their lowest point before waking. Women tend to have slightly higher temperatures than men – and, as anyone who has used a thermometer to track fertility knows, a woman’s basal body temperature (her lowest temperature in a 24-hour period, upon waking) will show a small spike shortly after ovulation.
Unless a person is sick, their body temperature will stay within a tight range. One reason it’s important to have a constant body temperature has to do with enzymes, which are proteins that speed up specific chemical reactions in our bodies. Enzymes are very sensitive to heat, and if their environment were to become too hot or too cold, they might stop working – and so would we!
If your body temperature does change, it’s usually due either to a fever in response to an infection or due to external temperatures that are too extreme for your body to cope with (think hypothermia or heatstroke).
Diabetes may also affect your body temperature if blood glucose levels aren’t kept in check. That’s because chronically high blood sugar levels can damage the nerves that help regulate our body temperature, including those that control our sweat glands. Sweat is one of the main ways that our bodies cool us off in hot weather; if an individual can’t properly sweat, their body temperature may rise dangerously high.
Diabetic nerve damage may also make someone feel hot or cold, even if their body temperature is fine. In hands and feet, this damage can cause both numbness and painful burning sensations and may make it difficult to sense changes in temperature. Chronically high blood glucose levels may also damage the small vessels that supply blood to hands and feet – and this reduced blood supply will make them feel cold.
In addition to diabetes, there are also several other medical conditions that might lead to cold or numb hands and feet. These include hypothyroidism (an autoimmune disease particularly common in people with type 1 diabetes) and Raynaud’s syndrome, a disease in which the blood vessels that supply blood to the skin overly constrict in response to cold temperatures or stress. This can make fingers and toes feel cold, go numb and sometimes even change color.
The bottom line? If you feel like you’re constantly colder or hotter than the people around you, talk with your healthcare professional to rule out any underlying medical condition. And if you live with type 1 or type 2 diabetes, do your best to keep your blood glucose levels in a safe and healthy range – it may help keep your body temperature steady, too.
Catherine Price is a freelance journalist and type 1 diabetic who has written for The New York Times, Slate, Popular Science and O Magazine, among others. Her newest book, Vitamania: Our Obsessive Quest for Nutritional Perfection, is available from Penguin Press. She blogs about diabetes at ASweetLife.org and you can follow her on Twitter @Catherine_Price. Price is a paid contributor for The DX. All opinions contained in this article reflect those of the contributor and interviewee, and not of Sanofi US, its employees, agencies, or affiliates.
© 2016 The DX: The Diabetes Experience