98.6F/37C Degrees Is A Normal Body Temperature, Right? Not Quite.
September 5, 2018 5:00 AM   Subscribe

You wake up at 6 am feeling achy and chilled. Unsure if you’re sick or just sleep-deprived, you reach for a thermometer. It beeps at 99°F/37.2°C, so you groan and roll out of bed and get ready for work. Because that’s not a fever. Is it? Yes, it is. Forget everything you know about normal body temperature and fever, starting with 98.6°F/37°C. That’s an antiquated number based on a flawed study from 1868 (yes, 150 years ago). The facts about fever are a lot more complicated. [slWired]

Paywalled study referenced from Journal of General Internal Medicine.
posted by ellieBOA (52 comments total) 35 users marked this as a favorite
 
Does anyone know of a website somewhere where you can paste a URL, and it turns all the Fahrenheits to Celsius in a readable way? Thanks, ellieBOA, for at least putting conversions in your post. (End Derail)
posted by pipeski at 5:28 AM on September 5, 2018 [10 favorites]


Other fun facts about fevers: idiopathic pediatric fever (that is to say, your >3-month-old human has a fever with no other attendant symptoms) is not actually a cause for alarm, and does not necessitate a trip to urgent care even if it's a really high fever. Under normal circumstances, the mechanism that causes fevers isn't capable of causing your body temperature to go high enough to do any lasting damage. Internal temperature regulation methods are wacky, man.

Why yes my 1-year-old DID hit a temperature of 105.1 last month, and the doctor DID explicitly told us not to take him to the ER unless there were other symptoms, why do you ask?
posted by Mayor West at 5:30 AM on September 5, 2018 [9 favorites]


DuckDuckGo has good converters. I linked to an F-to-C conversion for ease.
posted by fraula at 5:30 AM on September 5, 2018


pipeski, I am not American so will always need a conversion!
posted by ellieBOA at 5:31 AM on September 5, 2018 [1 favorite]


That Wired link is broken for me.

Edit: whoops now it works.
posted by stupidsexyFlanders at 5:34 AM on September 5, 2018


It's pretty simple and logical. 0F is the temperature of an equal mixture of ice, salt and water, and 100F is the estimated body temperature of the scientist who invented the scale.
posted by thelonius at 5:38 AM on September 5, 2018 [19 favorites]


Yeah, it was pretty funny finding out that the canonical 98.6°F every American grows up with is based on a conversion from 37°C (only two significant figures).
posted by DoctorFedora at 5:46 AM on September 5, 2018 [3 favorites]


IIRC whatever Fahrenheit thought/decided was normal body temperature was set to 96 with the idea that it would be easy to divide the temperature scale into many different subdivisions, like time measures being sexagesimal.
posted by GCU Sweet and Full of Grace at 5:55 AM on September 5, 2018 [6 favorites]


I'm super tempted to send this to my mother, who never believed me when I said I was sick because I never seemed to run a fever. It was variable all along!
posted by dinty_moore at 6:04 AM on September 5, 2018 [9 favorites]


I grew up taught that the healthy baseline is 36.6ºC. No idea where they got that particular figure.
posted by acb at 6:13 AM on September 5, 2018 [1 favorite]


I am an American scientist, which means that I'm always stuck between two temperature scales (or, really, three, because I mostly use Kelvin in my work). That said, I quite like the Fahrenheit scale for daily air temperatures. This reason for this was best described by the German colleague of a friend who said, "I actually think that Fahrenheit makes a lot of sense. 0 degrees is really fucking cold and 100 degrees is really fucking hot."
posted by Betelgeuse at 6:14 AM on September 5, 2018 [64 favorites]


Yeah, try telling doctors that you usually run around 96F and a temp of 100F means you feel like absolute and total crap and you are really sick. They're always like, "Well, 100F isn't a fever, so *shrug*!"
posted by cooker girl at 6:25 AM on September 5, 2018 [26 favorites]


IIRC whatever Fahrenheit thought/decided was normal body temperature was set to 96 with the idea that it would be easy to divide the temperature scale into many different subdivisions, like time measures being sexagesimal.

If the Wikipedia version can be trusted, he had 32 = freezing, 96 = body temperature. The difference between them is 64, which is a power of 2, so it's easy to mark off degrees by just taking the midpoint over and over.
posted by madcaptenor at 6:41 AM on September 5, 2018 [3 favorites]


0 degrees is really fucking cold and 100 degrees is really fucking hot.

Also true of Celsius.
posted by rodlymight at 6:50 AM on September 5, 2018 [36 favorites]


This article doesn't even mention that the 98.6 was a conversion (adding incorrect accuracy) from C, though.
posted by jeather at 6:52 AM on September 5, 2018


Yeah, try telling doctors that you usually run around 96F and a temp of 100F means you feel like absolute and total crap and you are really sick. They're always like, "Well, 100F isn't a fever, so *shrug*!

Jesus pants, I'm sorry you heard that. I heard that one degree either way was all right, but not that. Doctors are supposed to judge on "feverishness," too, like the article says.

It makes me happy that a doctor learned that one of the actual thermometers of Dr. Wunderlich was in the Mutter Museum, and tested it to find out it was miscalibrated all along. The Mutter is generally known as an upscale house of horrors -- which it is, too, you should go see it -- but it is an important scientific resource.

Personally, I always thought I must have a cooler body temperature than most people (probably because of something I did wrong) because if I'm not sick, my temperature is about a degree low. Now I can see it's so normal that there's no need to notice.
posted by Countess Elena at 6:54 AM on September 5, 2018 [9 favorites]


Handy reference guide:

Fahrenheit:
0° = Damn cold out
100° = Unpleasantly hot out*

Celsius:
0° = Pretty cold out
100° = Dead

Kelvin:
0 = Dead
100 = Dead



*Except in Arizona, when it typically has to get up around 110° for us to start complaining.
posted by darkstar at 6:56 AM on September 5, 2018 [98 favorites]


Damn. I've always thought I was unique because my body temp was always below 98F. Turns out I'm just like everybody else after all.
posted by COD at 6:57 AM on September 5, 2018 [7 favorites]


Celsius:
0° = Pretty cold out


In October or November, sure. In March, it's juuuuust about "driving with the windows down" weather.
posted by uncleozzy at 7:00 AM on September 5, 2018 [23 favorites]


0 degrees is really fucking cold and 100 degrees is really fucking hot.

Also true of Celsius.


There's nowhere on Earth that has air temperatures of 100°C (whereas 100°F/38°C is an upper temperature boundary for many climates), which is why Betelgeuse mentioned that they liked Fahrenheit for "daily air temperatures," not just all temperatures.
posted by andrewesque at 7:07 AM on September 5, 2018 [4 favorites]


My normal temp runs between 96 and 97.lownumber, so damn skippy I feel feverish at 99+.

I started school when there was a push for the U.S. converting to metric/Celsius, so they started teaching us that and then just stopped without warning after a couple of years. And then I grew up just south of the U.S./Canada border, so sometimes I'd hear/read one scale, sometimes another, and sometimes both. You would think that would make me more flexible, but the result is I'm just never 100% sure what the temperature is anywhere, even if I know where the speaker/writer is from.
posted by The Underpants Monster at 7:08 AM on September 5, 2018 [5 favorites]


Except in Arizona, when it typically has to get up around 110° for us to start complaining.

I know that "It's a dry heat" is a cliché, but I've traveled to the Southwest just often enough to appreciate that some clichés become cliché for a reason.
posted by The Underpants Monster at 7:12 AM on September 5, 2018 [6 favorites]


a push for the U.S. converting to metric/Celsius

They got as far as soda bottles, at least
posted by thelonius at 7:12 AM on September 5, 2018 [5 favorites]


Let's not forget drug dealers.
posted by acb at 7:14 AM on September 5, 2018 [7 favorites]


my favorite way to fuck with our engineering co-op students is to work an ounce to grams conversion question into casual conversation and see who immediately blurts out 28
posted by dudemanlives at 7:20 AM on September 5, 2018 [16 favorites]


36.6 is supposed to be normal temperature for armpit measurements. Apparently it gets taught in countries where it used to be the dominant measurement method, including Eastern Europe. I used to be so confused by Western cartoons showing mouth measurement.

(Now, thankfully, everyone's switched to forehead/ear.)
posted by I claim sanctuary at 7:27 AM on September 5, 2018 [2 favorites]



Celsius:
0° = Pretty cold out

In October or November, sure. In March, it's juuuuust about "driving with the windows down" weather.


I believe the technical term is 'might bit chilly out now'
posted by dinty_moore at 7:41 AM on September 5, 2018 [2 favorites]


You can blame the stalled move to metric on Ronald Reagan who dismantled the Metric Board in 1982.
posted by octothorpe at 8:05 AM on September 5, 2018 [14 favorites]


I wonder whether people in Britain will, post-Brexit, find themselves having to get reacquainted with temperatures in Fahrenheit. Non-metric weights and measures are the second most popular thing the ascendant gammons want to bring back (after the death penalty and before pre-decimal currency and the cane in schools), and while this will mostly be an end to supermarket goods being listed in grams or litres, if comprehensively implemented, it would mean a move away from Celsius. Perhaps we'll soon see helpful guides to what Fahrenheit temperatures feel like in the Evening Standard/Metro.
posted by acb at 8:12 AM on September 5, 2018 [3 favorites]


You can blame the stalled move to metric on Ronald Reagan who dismantled the Metric Board in 1982.

Dammit, that fucker again!
posted by The Underpants Monster at 8:21 AM on September 5, 2018 [24 favorites]


This is super interesting. I had a baaaad case of strep throat last week and while my thermometer only ever gave me a happy face, I could SWEAR I had a fever. I had everything else that comes along with a fever - the sweating, the restlessness, the inability to thermoregulate, the... well, the feverishness.

I learned something today. Good stuff.
posted by arcticwoman at 9:13 AM on September 5, 2018 [5 favorites]


Maybe I'm the only one here who runs hot—99-point-something on a good day. It seems to drop into "normal" range when I'm feeling a bit ill.
posted by Flexagon at 9:34 AM on September 5, 2018 [1 favorite]


Years ago, I'd come across info about how inaccurate the 98.6 number was, and how a "bad fever" wasn't any particular number - so when I had small children, I didn't have thermometers in the house.

Advice nurses on the phone hated me, but I stuck with it - I knew the difference between "a bit warm" and "wow that's hot," and I knew that fever alone wasn't a red-flag symptom, just something that meant "get rest and drink liquids," and watch out for other things like aches, coughing, extreme tiredness, and so on.

End result: I now have adult children who don't believe that there's a magic number that means "healthy." Yay.
posted by ErisLordFreedom at 10:05 AM on September 5, 2018 [8 favorites]


Imperial measures are more useful than celsius for most simple human uses. A foot is a convenient measure for human scale things like height and the size of rooms, and divides gracefully into halves, thirds, and quarters. A cup is a natural human portion size, while liters are too big and deciliters too small. Fahrenheit gives you finer temperature gradients in the zone that humans mostly live in. And so on.

It's just that it's absolutely terrible for any complicated calculations.
posted by tavella at 10:11 AM on September 5, 2018 [12 favorites]


I use google to convert, searching 100C = F and it returns 212F.

My kid had recurring low-grade fevers - up just a degree F or so, for a while. He always got cranky, so they weren't *nothing* but we never found a cause. Fever is a really useful indicator, it just turns out that humans have a range.

Also, docs should trust Moms and Dads.
posted by theora55 at 10:28 AM on September 5, 2018


You may think Celsius is superior to Fahrenheit, but consider:
69°F = nice
69 C = deadly
posted by ckape at 10:33 AM on September 5, 2018 [4 favorites]


In college I regularly ran about 96.5° F (35.8° C). For a while the clinic on campus used these weird strip thermometers that didn't register temperatures that low, so whenever I had to go in for something there was always a question of whether my temperature would even be high enough to register. Now I run around 97.2° F (36.2° C). I consider anything over a 99.2° F reading (37.3° C) a fever for me, so it's always extra alarming when it still manages to spike to 104° F (40° C). I'm supposed to run cold, dammit!
posted by fedward at 11:21 AM on September 5, 2018


-40oC = very cold
-40oF = just as cold, but the political climate is potentially worse
posted by klausman at 11:52 AM on September 5, 2018 [41 favorites]


As someone who has lived in North Dakota and Minnesota nearly all my life, 0°C means "people wear shorts to the grocery store" and "my coat is too warm for this weather" weather.

Eh, I guess 0°F still means "people wear shorts to the grocery store" but people in warm coats give those people funny looks.
posted by AzraelBrown at 12:01 PM on September 5, 2018 [2 favorites]


I've lived in Florida for 35 years. Anything below 50ºF is winter.
posted by jeporter99 at 12:11 PM on September 5, 2018 [3 favorites]


Sigh ... my "normal" body temp is usually about 98 F or 98.2 F. When I get sick, my temperature tends to drop, not rise. Try convincing a doctor you are really sick when your temperature is 96 F. Eventually, my GP got familiar enough with me to understand this, and also to know that the time I came in with a temperature of 99.2 F that I was really extremely ill. It becomes an issue again whenever I get treated by a strange doctor (and it is hard work convincing people of this weirdness when you are pretty sick at the time).
posted by gudrun at 12:13 PM on September 5, 2018


While our ability to detect and manage fever has evolved since its conceptualization in the 5th century BC, controversy remains over the best evidence-based practices regarding if and when to treat this physiologic derangement in the critically ill. There are two basic fields of thought: (I) fever should be suppressed because its metabolic costs outweigh its potential physiologic benefit in an already stressed host; vs. (II) fever is a protective adaptive response that should be allowed to run its course under most circumstances. The latter approach, sometime referred to as the “let it ride” philosophy, has been supported by several recent randomized controlled trials like that of Young et al. [2015], which are challenging earlier observational studies and may be pushing the pendulum away from the Pavlovian treatment response.

I had this year's flu and was given a fever pill like Advil, and in a few days I felt much, much worse as the fever and symptoms came back with a vengeance whenever the meds wore off, bad enough that I couldn't sleep/eat properly to fight the infection, i.e. "an already stressed host". Then I started reading and some doctors theorize that suppressing a fever has the twofold effect of leaving your immune cells at a suboptimal temperature for them, plus a lower temperature increases cellular destructive activity by the flu virus in your body. And that's why it's better to let a moderately horrible fever run its course, if you can. It's interesting cause you're kind of planning your own suffering in terms of duration times the magnitude.
posted by polymodus at 1:11 PM on September 5, 2018 [1 favorite]


If the Wikipedia version can be trusted, he had 32 = freezing, 96 = body temperature. The difference between them is 64, which is a power of 2, so it's easy to mark off degrees by just taking the midpoint over and over.

Lies. It's 32...212 for the liquid phase of water at sea level, by definition. And 212-32=180, which is divisible all kinds of ways.

100 being body temperature or Texas or whatever is surely a coincidence. 100 doesn't have any special meaning in any other imperial unit. Not even a hunderedweight.
posted by Pruitt-Igoe at 1:35 PM on September 5, 2018 [1 favorite]


"Yeah, try telling doctors that you usually run around 96F and a temp of 100F means you feel like absolute and total crap and you are really sick. They're always like, "Well, 100F isn't a fever, so *shrug*!""

This is how I ended up hospitalized for over a week with mono. As a little kid I was really prone to ear infections, usually diagnosed when I was sobbing in the nurse's office because my ear hurt so badly, but I didn't have a fever, but I was so hysterical from pain they'd call my mother because they didn't know what else to do, and she'd tell them SHE NEVER RUNS FEVERS and they'd swear to remember that next time but never did.

Anyway in college I got super-sick and I went to student health and they were like, "You don't have a fever, it's probably just a cold." I protested that I don't ever run fevers and was ignored. A few days later I went back because it was so much worse and my throat was so swollen I could barely swallow food, and they said, "Look, you don't have a fever, try sleeping more." "OKAY BUT I DON'T EVER RUN FEVERS AND ALL I'VE BEEN DOING IS SLEEPING." A few days later I went to the emergency room because I could barely swallow water and hadn't eaten solid food in over a day, and I told them all of this and they said, "Well, you don't have a fever, but it's might be strep, here's some antibiotics." "I DON'T EVER RUN FEVERS AND IT DOESN'T FEEL LIKE STREP." "Just take the antibiotics, they'll help." So I do and two days later I still haven't eaten, my throat is so swollen I can barely talk, and I wake up feeling like I'M LITERALLY DYING (which was apparently due to the antibiotic trying to process through my wildly overworked liver). I hobble across campus to the student health center, sitting down six times on the way, hobble in, and the intake nurse looks horrified and goes, "YOU HAVE MONO!" and demands the doctor run the test, and the doctor objects, "But she doesn't have a fever!" and the nurse says, "Look how pale she is, just do the test!"

Anyway, the nurse was right, and I was SO sick from the mono and lack of food and dehydration and misprescribed antibiotics, that I was hospitalized for several days and had to be put on an IV and was semi-conscious for 48 hours and almost had to withdraw from college.

I'm a lot more assertive these days about insisting I never run "official" fevers and demanding the doctor at least look at my throat or ear or whatever. My normal body temperature seems to be around 96 and a bit (my thermometer likes 96.4, my doctor's likes 96.7); if I'm running a 99 I can barely get out of bed.

In fact during two of my three C-sections the medical staff got real grumpy about how low my temperature was and how it was refusing to come back up out of the danger zone. Like I guess it's normal for it to dip during the surgery -- the room is cold, you're immobilized, there's drugs -- but it's supposed to come back up to a certain range within an hour after, and mine just wasn't. I guess they wanted me at 36 C before they'd discharge me from recovery, which is 96.8, but my temperature is below that on the regular and my body didn't see any reason while I was lying completely still to get above that!
posted by Eyebrows McGee at 2:15 PM on September 5, 2018 [13 favorites]


This is very timely for me. Just last night I watched the episode of Adam Ruins Everything, Adam Ruins Science that talked about, among other things, how we rely on old scientific studies that either can't be reproduced or that no one bothers trying to reproduce.
posted by ceejaytee at 3:25 PM on September 5, 2018


I understand why, logistically, they used oral thermometers, but were these thermometers calibrated? Or were they whatever the people had at home? I can take my temperature with three different home thermometers and get three different results (all within 0.5 degrees of each other, but that's a lot when you're talking about redefining fever.)

The other thing to keep in mind is that as soon as your temperature starts to rise, you start to breathe faster (pant imperceptibly), and by moving 70F air in and out of your 99F body, you make your already-inaccurate oral thermometer even less accurate. There's a reason why they invented those ear-wand thermometer things.
posted by basalganglia at 4:54 PM on September 5, 2018


I'm another person that runs cold, or at least I did in my 30s, when I took my temperature twice a day for a month and found it to average about 96. It came in very handy at school, when I I used to wobble into the nurse's office claiming to feel ill. She'd take my temperature, look little bewildered, say "well, you seem to be a bit chilled" and send me home for the afternoon. I had to be careful not to pull this stunt too often, but it was very useful for getting off games.

When it comes to weather, I tend to think of cold weather in Centigrade (5 below is pretty cold here) and hot weather in Fahrenheit (hot is 80 or higher, like this summer), but I have no idea why.
posted by Fuchsoid at 5:02 PM on September 5, 2018


Celsius:
0° = Pretty cold out

In October or November, sure. In March, it's juuuuust about "driving with the windows down" weather.


Nope, 0°C is still pretty damn cold in March, given we still get plenty of 30°+ days in March. And last week we were all complaining about how it got down to 1° or 2° because that just isn't supposed to happen when the calendar says it's spring!
posted by Athanassiel at 6:40 PM on September 5, 2018


A jerky doctor once said to me "you can't say you have a fever unless you've measured your temperature". Nice to see him debunked here.
posted by nnethercote at 12:05 AM on September 6, 2018 [2 favorites]


When I was in late 3rd grade, visiting my beloved baby doctor for yet another shot of pencillin for strep, with a fever of 103, he said "that's not so bad for you. See" pointing to a corner of my chart where there was something written in red "your normal is 99 and a half."

After I got sick just past six months with terrible ear infections, I started running temps of 106 which could only be controlled with ice baths, and 3 different doctors advised my mother to let me go, but she wouldn't. My left ear was ultimately x-rayed to knock down the infection, which worked, but by then I'd "forgotten" how to walk and talk, and had to learn all over again.

Now my temperature seems to be about 99 normally, but I feel extremely hot when I get upset, and my partner and I have had to pull over and let me walk around outside the car many times when we've had an argument, because the windows got fogged up so much it was impossible to drive.
posted by jamjam at 1:21 AM on September 6, 2018 [2 favorites]



Yeah, try telling doctors that you usually run around 96F and a temp of 100F means you feel like absolute and total crap and you are really sick. They're always like, "Well, 100F isn't a fever, so *shrug*!"
posted by cooker girl at 6:25 AM


Cooker girl, YES. My whole life my temp has run between 96.5 to 97.6, give or take. My mother knew this; once when I felt sick at school, the nurse took my temperature, and at 99 degrees scoffed at my insistence that I had a fever. She finally phoned my mother, who confirmed that indeed, that was a fever for me.

Most recently, at a visit for a cold to a walk in clinic, when I informed the young doctor that 99 degrees was a fever for me, that my usual body temperature was around 97 degrees, he literally looked at me sideways and said "How often do you take your temperature that you would think that?" and did not take me seriously. I was rather offended. I'm 52 years old! I took my temperature daily 26 years ago when I was plotting my ovulation in anticipation of conceiving my first child. How dare he question my knowledge of my own body!
posted by annieb at 8:29 AM on September 6, 2018 [6 favorites]


My temp is usually around 97
posted by 922257033c4a0f3cecdbd819a46d626999d1af4a at 4:41 PM on September 6, 2018


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