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Old 10-05-2009, 07:01 PM
Join Date: Dec 1999
Location: Southern CA
Posts: 3,561
A fever is defined as a temp over 100.4--no matter what your baseline?

Ugh. I have been fighting a thing for 10 days now. With the swine flu in the forefront of my doc's thoughts (especially since I'm 6mos pregnant), they were very preoccupied with my symptoms and temperature. By definition, I do not have a fever. When my OB checked me, my temp was 97.7--normal for me. Now that it has risen to 99.5 (standard "fever" for me), it's still not considered a fever as it hasn't crossed the 100.4 threshold.

I'm not much concerned--it's a bug I'll fight off--but I'm surprised that the doc said the standard is 100.4, regardless of the patient's normal baseline. (98.6 is an average, I know.)

In 15 years, my temperature has gone over 100 twice that I can recall for certain; there may have been a third. Even when I had pneumonia, my temperature never went above 99.5.

So--if "normal" body temperature of 98.6 is actually just an average, wouldn't 100.4 as a "normal" standard for fever be an average as well? I'm confused why one is considered flexible, and the other set in stone. Not that it matters all the much to me sickie-wise; the treatment is the same. I just found it odd.

Meanwhile, mmmmpppphhhh.
Old 10-05-2009, 08:40 PM
Charter Member
Join Date: Jul 2001
Location: SE Metro Atlanta, GA, USA
Posts: 1,354
From what I learned in school...

There is a range for normal temperature, which depends both on the person, and where the temperature was taken. A fever is considered a temperature outside the range. Why that is, I don't know. However, here is the list of normal temperatures by site tested.
  • Rectal: 97.9F - 100.4F, Fever >100.4F
  • Oral: 95.9F - 99.5F. Fever >99.7F
  • Axillary (under arm): 94.5F - 99.2F, Fever >99.3F
  • Tympanic (Ear): 96.3F - 99.9F, Fever >100F

So, depending on where you are taking your temperature from, depends on what's considered a fever.
Old 10-05-2009, 10:43 PM
Join Date: Jun 2003
Posts: 1,444
This is something that drives me mad, too. I am a cold person it seems, with my underarm temperature being in the range of 35.8 (96-ish) to the low 36's. When my son and I went to the hospital (in rural Japan) five years ago with flu symptoms, his test came out positive and he got the Tamiflu etc. My temperature was 0.1 C below the "flu fever" threshold and my test came out negative. So despite being unable to actually sit up, I was told that "Flu is highly contagious so make sure to use barrier nursing methods when caring for your son." I was so frustrated that I just wept.

The same son was just diagnosed with Swine Flu (16 out of 34 kids in his class have it and over 60 in his school so it has closed for a week - eep!) and this time they were saying an axillary temperature of 38.5C (101 F) or more was indicative of flu. His temperature went up to 40.6 C (105F) taken under his arm on the second night of the flu. Really scary. The fever came on really fast though - two hours from his first saying he felt bad and his having a fever of about 100F to him having a temperature of 103F.
Old 10-05-2009, 11:29 PM
Join Date: Sep 1999
Location: Zeelandia
Posts: 9,652
Originally Posted by Hirka T'Bawa View Post
  • Rectal: 97.9F - 100.4F, Fever >100.4F
  • Oral: 95.9F - 99.5F. Fever >99.7F
  • Axillary (under arm): 94.5F - 99.2F, Fever >99.3F
  • Tympanic (Ear): 96.3F - 99.9F, Fever >100F
A lot of public places around here have someone at the doorway ready to take your temperature with a device they put near your forehead. Usually not even *on* the forehead, but up to a centimeter away. What would be the temperature range for those?

BTW, I always found it very mildly amusing that 100.4 rule sounds like such a precise and finely tuned threshold, 'til you realize it's only the Fahrenheit version of a fat rounded off number in Centigrade ((100.4 -32) * 5/9 = 38)
Old 10-06-2009, 03:35 AM
Join Date: Sep 2009
Location: The Internet. Since '84.
Posts: 6,460
Honestly, this just pisses me off.

If my "normal" temperature is X, X-.1 or X +.1 should not be considered unusual.

However, when I go to a doctor, and they check my temp, and decide I do/don't have a fever, I remind them that I need 9-10 hours of sleep vs the "normal" 8 hours. Also, that one particular front tooth is the 3rd vs the canonical 2.

I'm sick, I know it, and they should not shunt me as an aside just because I do not reflect "the average."

Last edited by Superhal; 10-06-2009 at 03:36 AM.
Old 10-06-2009, 05:15 AM
Join Date: Apr 2008
Location: Sydney, Australia
Posts: 110
Maybe the definition of fever at that temperature comes from a temperature at which it is known that enzymes may start to denature? We all have the same enzymes which would explain why a "fever" is defined at a specific temperature. Just a guess.
Old 10-06-2009, 01:27 PM
Join Date: Dec 2008
Posts: 8,867
Originally Posted by Blazric Jones View Post
Maybe the definition of fever at that temperature comes from a temperature at which it is known that enzymes may start to denature? We all have the same enzymes which would explain why a "fever" is defined at a specific temperature. Just a guess.
This is more along the lines that medical pros use, I think. The relative difference in temperature might measure how sick you are, but actual damage that would be life threatening is really based on the actual temperature, not a relative difference. Putting someone in an ice bath to cool them down doesn't make them less sick, but it does make them less hot and can save their life.

Part of the problem with comparing a fever to a baseline is that the doctor rarely knows the baseline and patients can't always be trusted. Even if the patients charts their temp every day, does the doctor know whether they're taking it correctly, with an accurate thermometer?

I think a survey showed that something like 80% of people believe they heal more quickly than average. Clearly, at least 30% of us are optimists who really don't know what we're talking about.
Old 10-06-2009, 01:43 PM
Join Date: Mar 2000
Posts: 2,926
I think part of it depends on your doc & your relationship with em.

I have two people in my family that normally run low temperatures. Both have discussed this with their docs, & the docs will take that into account when they have a fever. They do have to remind the docs every time, but it does get considered after that.

Even more fun are the members of my family who often run "reverse fever". That is, when they get sick and feel feverish, their temps often drop rather than rise. It's the weirdest thing.

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