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

January 2, 2008
Normal body temperature can vary slightly from person to person. [Credit:Xavi Sanchez]
Normal body temperature can vary slightly from person to person. [Credit:Xavi Sanchez]

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.

About the Author

Jessie Jiang

Jessie has a B.S. degree in chemistry from Peking University in China, where she initially did research on molecular magnetic materials but gradually switched her interest to science writing. Before joining SHERP, she held internships as a reporter at the English-language Shanghai Daily, and at Ogilvy Communications’ Beijing office. She loves writing, and hopes to become a science editor someday as her father has been for decades.



Jene says:

Why do people keep complaining here when nobody is answering? I have fibromuscular dysplasia and there’s no cure. I was just wondering if a circulatory problem was causing a low temp reading. I Have multiple brain aneurysms…already know I’m dying…oh well.

Anna says:

Why am do i always feel so hot? My siblings and mother always said i radiated heat ever since i was a child. Im 18 years old and im a female. Im not overweight. Diabetes, high blood pressure, chrones, and graves disease run in the family. But im the only one who is always hot. Can anyone enlighten me please?

rolo says:

Hi ever since I was a child my temp has been constant 87 degrees ive always been healtyh n athletic tho I’m 21 now nothing has changed I have a strong immune system and only catch 1 virus a year on average I also heal pretty quickly Wat do u think?

Darlene says:

If you look on the Internet for Hypothyroidism you will find signs of low body temperature. Generally, the average temperature of an adult with a healthy thyroid and a healthy metabolism is 98.6 degrees Fahrenheit or 37.0 degrees Celsius, and that occurs around mid-afternoon or 3 pm. So if you take your mid-afternoon temp and find it in low 98′s or even in the 97′s, you have been given a strong clue that you may be hypothyroid. And a few report their mid-afternoon temp being in the 96′s. BRRRR.
Another temperature clue occurs first thing in the morning before you raise from your bed. Dr. Broda Barnes, a doctor who paid attention to clinical presentation and prescribed the pre-reformulated Armour, found that a healthy before-rising morning basal temp should be between 97.8 – 98.2. If it’s higher, you may be hyperthyroid, and if it’s lower, you are most likely hypothyroid. He also recommended under-the-arm temperature testing, but patients have found oral to be just as effective.

Once you are on natural desiccated thyroid or T3-only, and are consistently raising your doses, you will see your temps climb to healthy levels with increasing feel-good symptoms to match. In many patients, reaching the average temp around 98.6 can happen before you are even on your optimal amount of desiccated thyroid or T3.

Thyroid patients have found Mercury thermometer quite useful and accurate as compared to most digital thermometers. Yes, some digitals are definitely better than others. It’s also important to leave it under your tongue long enough, i.e. up to five minutes. A second alternative: a Geratherm, which is a liquid non-mercury thermometer. May be more accurate than digitals. Bulky.

Along with Hypothyroidism there is slow metabolism and weight gain, feeling tired along with feeling cold. If you have these problems you should get your thyroids tested.

I believe some blood tests are not accurate…somewhere, I can’t remember where, so perhaps some blood expert can respond, I read a study where blood tests are performed and the readings/interpretation are supposed to be made after the blood is kept at body temperature, NOT room temperature…I have been diagnosed with MGUS..blood disease and am undergoing chemo…are my blood tests being conducted properly?

shweta says:

I want answers to my question…??
M 17 yrs old 5.1 height and weigh 57kg…
wenever i check my temp on electric thermometer it shows me 98.9…???
n wenever frnds hold me says ur body n hand is soo hot even i dnt hav fever…???
i dnt knw y m always warm…
i hav seen many frnds of myn in grlzzz…who r normal temp dey r nt at all warm…
y is it soo…??wether its normal to hav same temp (98.9°) evry day…???
i alwzz hav pimples on my face is dat bcoz of hot temp…
even my back is filled wid pimples…:(
i dnt lyk warm (hot) temp plzzz giv me some suggestion how to keep normal temp or cool body…..? :(

Shel says:

We are all posting our questions, but there is no venue for answering. We can only “Post a Comment”. I guess we could post our opinions on each other’s maladies, or hope someone with the knowledge and bravery to diagnose over the internet would come along and indulge us?

I am 23 years old and i was born with a heating condition and my normal body temp is a 97.6 and my body always over heats in the summer and all year round what is the cause of this i ha ve been trying to find out what has been causing it all my life and no one has been able to tell me and because of this condition i have had atleast 10 heat stokes in the course of 8 years and it seems like my condition is getting worse

C says:

I have always had a lower body temp. I have had all the tests for thyroid, anemia, etc and they came out fine. When I was a kid I had a bad flu. My mother took my temperature and it read, 101, which really meant I had the equivalent of a 103 fever since my normal body temperature is around 96. That is why I started having feverish hallucinations! Over the years that reaction was consistent, anytime my temp reached over 101 I would be having the same problem. It took a while for my parent to realize what the issue was. It’s really important that doctors and nurses be aware of this. When I do go to the doctor when I’m sick, I’m reporting to them that I have a fever, but they rely on that “average” as if it’s supposed to be the same for everyone and then they tell me it’s impossible I have a fever because my temperature is reading 98, not recognizing that I’m there at the doctors because I’m sick with a fever-who goes when they are well after all! My greatest concern is god forbid I have to go to the hospital or a nursing home, they might take my temperature and not realize I have a severe infection of fever because they don’t ask you what your base temperature is.

Dawna says:

Having read this I believed it was extremely enlightening.
I appreciate you taking the time and effort to put this short article together.
I once again find myself personally spending way too much time both reading and leaving comments.

But so what, it was still worth it!

Mac says:

My average temp. is about 97 degrees.

Right now, I have to say, “Estoy enferma” or “I am sick”. My temp is 100.2 right now, which means that to a normal person that’s 101.8.


Perhaps now that’s it nearly one a.m., I should really go to bed.

Julie says:

I had a perforated bowel in my 30’s and ended up with a colostomy. The colostomy was reversed. I have also had a bowel obstruction. All my life I have battled Diverticuloses and have been hospitalized many times for acute Diverticulitis. I narrowly escaped two more colostomy’s.

For a few days now, I have been spiking a low grade fever, with a slight abdominal discomfort. I always keep watch on my temp, as that could be a flare-up of Diverticulitis. I still feel feverish to-day….However I was astonished to find, my temp was 36.0. That has never happened to me before. My temp has always been my barometer for, a bowel infection. Taking my temp as I speak, my temp is 36.6. I’m all over the place. I need a new barometer of some sort, to watch for an infection in my bowel.

S.N.DUA says:

My mother age around 67 years.she always ask that I feel fever in my body and whole body pain in musles.I try to visit several General Phshysian and neruo and physiotherphy doctor but I am not satisfied.No sugar no thyriod problem.I request to all of you please tell how to solve this problem.S.N.DUA-DELHI -9873366251 email


My temp. keeps reading 97.1 or lower but im burning up on the outside it’s gotten up to 103 at times on my skin and gets when I lay down at night my body heats up so bad even with the airconditioner on I can’t even let anyone sleep next to me my body gets so hot and im only 29 years old. Can you give me a clue what could be it is or if its gonna get worse I have many many health problems for a 29 years old even had a stoke already been in a coma been a diabetic but I got that under control my thyroid is back to normal, and my gallbladder is back to normal it filled up with gallstones so bad they were going to do emergency surgery twice but I never could get a ride back ‘that hospital. I don’t know where else to turn to get an answer as to what to do about it to help it or what it could possibly be.


My temp. keeps reading 97.1 or lower but im burning up on the outside it’s gotten up to 103 at times on my skin and gets when I lay down at night my body heats up so bad even with the airconditioner on I can’t even let anyone sleep next to me my body gets so hot and im only 29 years old. Can you give me a clue what could be it is or if its gonna get worse I have many many health problems for a 29 years old even had a stoke already been in a coma been a diabetic but I got that under control my thyroid is back to normal, and my gallbladder is back to normal it filled up with gallstones so bad they were going to do emergency surgery twice but I never could get a ride back ‘that hospital. I don’t know where else to turn to get an answer as to what to do about it to help it or what it could possibly be.

DM says:

I have a consistent body temperature of 94.7. I am 39 years old and on 125mcg Synthroid. I am doing labs every 3 months and my TSH is now 0.8. If my thyroid is being treated, my body temperature should be elevated, correct? I am always freezing cold. I turn on heaters in the summer time. My nails are purple; hands and feet like an ice box. I have never conceived in my life.

My endocrinologist thinks in black and white. My TSH is in normal range now – her job is done. I’ve seen so many doctors – they all think the same way.

athiframdan says:

Why blood temperature is greater(38degree cel) than normal body temperature( 37degree cel)????
Any experts please explain??


i am feeling cold in fact in summer also,even my blood pressure is normal at all time.what does it mean?
mail me please with reason.

Amber says:

My body temperature has always been quite lower than every person I know. The weird part is that I do not have any form of diabetes or any underlying medical condition. All I know is that I have asthma and very horrible farsightedness. Any ideas of what the cause of low body temperature could mean?

Nancy rivera says:

I just wanted to add and my apologies if it’s been stated already. Low body temperature was an indicator for thyroid issues, they say iodine deficiencies is at the root of the issue and is a necessary for the thyroid function. If you have fibroids in your breat in would be a bid indicator that you are needing iodine.

Nancy rivera says:

In the book hypothyroidism 2 by Mark Starr he claims that low body temperature is only caused by thyroid issues. There is Mary Shomon who is an expert in the thyroid who’s book living with hypothyroid had great info.

Good luck and hope this info leads you in the right direction.

parvathi says:

My son 1 yr 5 months baby. Now him tempeture is 100.1 this is normal. Fever starting range. May i know. Pls reply me with my mail.thank u…

Taylor says:

i have a very low, constant temperature that hovers around the 95 mark. It has been measured at 95.5 on a few different occasions and when it’s any higher than 96 or 97 I feel abnormally warm. I am almost 18 and a female. I have been tracking my Tempeture for months on random occasions when I feel fine and also I am using my sister as a control to see if the fluctuations are occurring in the themomter. They are not. She always reads in at a relatively normal temperature. It’s recently dipped into the 94 range but my parents refuse to get it checked out. Should I be worried? My blood type is A- and I do have an enlarged kidney if that makes a difference.

kevin says:

I am 50 years old and male.
When I lay down my body shows signs of a fever. My skin is very very hot, I sweat a lot whilst this process is going on. My partner, if we are in bed, wakes up and as to go into the other room. I can raise the temperature in the room by 2 degrees within 45mins.Does anyone have any idea what is going on!!!???
Many thanks

Margo Hart says:

Body temp 95.9 with cholls then in few hours to 97.6. What does this mean?

Beth Bishop says:

Most people think a normal body temperature is an oral temperature (by mouth) of 98.6°F (37°C). This is an average of normal body temperatures. Your normal temperature may actually be 1°F (0.6°C) or more above or below this. Also, your normal temperature changes by as much as 1°F (0.6°C) during the day, depending on how active you are and the time of day. Body temperature is very sensitive to hormone levels.

Chandra says:

My base temperature is 96.8. My grandpa’s was too and I believe my mother’s is as well. If I get a 98.6, I’m running a mild fever. But it’s good to know I’m not alone in the world.

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