Why does my normal body temperature always seem to be lower than 98.6 degrees? By how much do normal human body temperatures vary?
- Asks Lev from Detroit, MI
When the German physician, Carl Wunderlich, first reported 37 degrees Celsius (or 98.6 degrees Fahrenheit) as the average human body temperature in 1861, he claimed to have drawn his conclusion from more than a million armpit measurements of 25,000 patients. As unlikely as that sounds, it’s true that “normal body temperatures” are largely based on observation, and not any comprehensive theory.
In fact, normal body temperature not only varies between individuals, but also flutters within the same person with time of day and age, usually between 96.9 °F and 100 °F.
If you measure your own temperature at different parts of the body, say in your mouth and under your arms, you’ll notice that the temperatures are different. The general rule is that the thinner a body part is, the less contact it has with the outside environment, and therefore the higher temperature you’ll observe.
As with all other mammals, humans maintain a relatively constant temperature by breaking down carbohydrates, proteins and fats for energy, much like a power plant that burns coal for energy. The process occurs inside our cells, where oxygen, water and nutrients chemically react to produce carbon dioxide, energy and heat. That heat is then absorbed by blood and distributed throughout the body via a network of veins, arteries and capillaries.
The elasticity of those capillaries plays a central role in our ability to maintain constant body temperatures. When there’s too much heat in the body, our capillaries automatically expand and increase the blood flow to the skin, allowing the excess heat to transfer to the air. This is why people become flushed after working out. Conversely, when we don’t have enough energy to balance out the heat loss, capillaries narrow to slow down the blood flow and therefore minimize energy escape.
However, not all fluctuations of our body temperature fall under the control of blood vessels. For example, you are likely to have a higher temperature right after a 100-meter sprint than when you are fast asleep. Intense physical activities temporarily boost your metabolic rate as your body burns more fuels to balance your energy consumption.
Body temperatures wax and wane with hormone levels, too. That’s why a woman’s basal body temperature, or her temperature on waking after a normal night’s sleep, is often used as an indicator of ovulation. Characterized by the surge of luteinizing hormone, a kind of hormone needed for proper reproductive function, ovulation usually increases basal body temperature by 0.4 °F to 1 °F.
Women also tend to have higher rectal body temperatures, or temperatures taken directly inside the body cavity, than men, according to a 2001 study by a group of Dutch scientists. They largely attributed the difference to women’s reproductive cycle, which may in turn explain why men and women have slightly different ways to maintain their body temperatures. Other possible explanations include different abilities to contract blood vessels and differences in resting metabolic rates.
Meanwhile, controlling body temperatures has recently emerged as a potential treatment for stroke. Clot-causing cells, the main culprit for blocking blood vessels and inducing stroke, were found to be less active at lower temperatures. The commonly accepted target temperature is now set at 91.4 °F, or 33 °C, but clinical trials are still underway in the search for optimal conditions for treatment.
While those treatments require a change in body temperature, it is generally true that a healthy person will have a fairly constant body temperature. In fact, it’s so important that your body spends 90 percent of its metabolic energy to make very sure that your temperature is as close to 98.6 °F as possible. So, even though you may feel hot or cold, or worry that your body temperature isn’t 98.6 °F all the time, rest assured, your body is working very hard to maintain that temperature.
Why am I always feeling so cold? I put on layers of clothing and even in rooms or places where others have only a t-shirts or so I seem to need at least a t-shirt and sweatshirt or sweater and even then often am cold. Also very often have cold feet. Thank you Rennie
rennie boersma, January 25, 2008 at 2:29 pmat 69 my temp is 96.6-i take diovan 320mg to lower my bp.since its purpose is to push circulation to extremities could this explain my low temp.
moore, January 30, 2008 at 3:17 pmage 77, tend to have oral temps in the 97’s. If temp goes to 98.8 or higher, I feel as if I have a fever–zlight dizzyness, ’spacey’ feeling, a bit of balance trouble. But doc says no fever unless temp hits 100.4. Can one have a fever with a lower temp as I feel I do?
Constance Eves, March 17, 2008 at 12:24 pmI am no doctor but dont somone of your age normally run a lower BP rate anyway? That would explain why you feel this way when your is higher that usual.♥
Shannon, March 18, 2008 at 5:09 pmThere is a lot of undiagnosed hypothyroidism out there! I had all kinds of wierd symptoms, twitching, sweating, cold, dizzy, weak and fatigued, and was told my thyroid was just fine.
Patricia, March 31, 2008 at 6:17 pmThen I got worse and in an emergency room was told my thyroid was not fine, but “sometimes the problem doesn’t show up on the tests for awhile.”
I got a ton of info from a site called
stopthethyroidmadness.com. The blood tests are by no means always accurate and synthetic thyroid sucks, to sum up.
I am 71. I find my temperature varies between 96-97 to 98.6 to 99. I feel feverish at 98.6 with body ache, aching backbone, do not feel like taking bath etc. I feel OK when temp around 97.6/98.
Naturally I have other multiple problems eg Apical Hyperotrophy, Diastolic Dysfunction, Hypertension, 40% heart blockages, Autonomous Nervous Dysfunction more at rest, peripheral neuropathty, dymelating, cervical, lumber and bent tail bone with denegeration of Discs, sensitive to gluten!, reducing caffeine tp reduce irritation of bowels, poor ballder pump with pain, simple kidney cyst Lt, frequent urination with disturbed sleep: Surgeries done tonsils, appendix, prsotrate, both inguinal hernias, urethera strictures, and bladder neck,frequent urination catarcat surgeries, high and low sugar varying between 71 to 260 with 4hours TT but controlled with food intake at medication, no thyroid problem , no HIV, no PSA, and so on.
Medication for heart and sugar and other from time to time.
Basic irksome problem is this low grade fever?
Prem P Batra, April 6, 2008 at 1:24 amMy husband is suffering (for about 2 yrs. from what seems to be a malfunctioning temperature gauge. He goes from hot to cold in a mattter of minutes. Has anyone suffered from this?
Colleen Brown, July 31, 2008 at 5:13 pmI’d like to know also why I’m always cold. I used to have this furnace that kept me warm and it seems once I hit puberty hit, the pilot ligh went out.
Megan, September 4, 2008 at 6:13 pmMy temperature has dropped to 97.7 most of the time. I was at the doctor and he said he gets very few patients with a temp. of 98.6 anymore. Most are running lower temps. This seems strange/ what is causing this?
kaci, October 14, 2008 at 8:33 pmI’m in good shape and have great health, but I am constantly colder than everyone else. I wear layers or have a blanket when others are in shorts and t-shirts. Why is this?
Joy Hales, October 15, 2008 at 10:50 pmI actually run quite cool for my age, I’m normally 95.6 – 96. I’ve lived in the desert all my life and I’m quite happy to wear short sleeves and shorts in 55 degree weather, but I can’t stand temps above 85 degrees (ironic to where I live). I’m just curious, does having a cooler temp then the average Joe affect my tolerance for cold or hot temperatures?
Cally, December 14, 2008 at 1:19 amPlease, please, please, could you send me a copy of this article. I have a longstanding debate with a collegiate.
Leslie Chevalier, January 5, 2009 at 5:51 pmCan you help me find information on the individual differences in normal human body temperature circadian fluctuations. Thank you in advance. Best regards.
miroslav, February 13, 2009 at 1:11 pmIn reply to Colleen Brown,July 31st, 2008 at 5:13 pm: I am 72. My temperature varies greatly. For example, in the past two days, it has bounced up and down repeatedly between 92.6 and 99.1. It has been doing this for over four years. No medical personel seem interested. It is driving me to distraction, literally. When at low temp extremes, it is difficult to focus, to remain physically and mentally balanced. It is ruining my life.
Gary Burdick, May 8, 2009 at 9:09 pm@Gary Burdick:
Highly fluctuating temperatures may be a sign of an adrenal insufficiency which is also often found with hypothyroidism.
Google “adrenal insufficiency” or “hypoadrenalism” as a starting point.
Of course, there may be other things but it might be a good place to start searching.
Luke, May 13, 2009 at 1:36 pmOver the years I have noticed that my body temperature is usually around 35-36 degrees. So I can be feverish without actually reaching the classic 38-39 degree temerature. This is the same for my brother and 2 sisters, as well as my mother. Could it be a genetic thing?
Naomi Juyn, May 26, 2009 at 10:12 amThis….doesnt look like gonna be an easy biology project to copy
Alexander, September 9, 2009 at 6:47 pm