Why does my elevated temperature not register at the doctor's office?
February 10, 2022 8:44 AM   Subscribe

For the last two years I have had a constant low-grade fever. It ranges from 99.5 to 100.9. It is never higher and never lower and likely associated with a rare immune disease I was diagnosed with. Prior to getting sick I had a normal body temperature. But when I go the doctor's office my temperature often doesn't register. Why might this be happening? [Also, I am not super interested in legislating if this qualifies as a fever, I'm wondering why there is a discrepancy in temperature readings.]

We have three thermometers in the house all of which work fine-- my kids and husband register as having regular body temperatures when they are well and fevers when they are sick. All the thermometers are consistent with as one another. (All three are ear thermometers, but different makes and models.)

However, at my doctor's visits they often say that say my temperature is normal or even low. I see a lot of different specialists, but their offices generally use under-the-tongue or forehead swipe thermometers and the under-the-tongue often feels pretty hasty-- once I asked the nurse to double check and, the second time, I did have an elevated temperature that matched the reading on our home thermometer.

One time as an experiment, I drank tea right before an appointment and still no elevated temperature. Weirdly, one specialist's office DOES consistently register the elevated temperature despite using the same thermometers as all the other offices.

I'd love to know what is going on. Partly, because I'm genuinely curious, but it's also been difficult to have one of my symptoms simply not register when I am seeking care. Thanks!
posted by jeszac to Health & Fitness (10 answers total)
Ear and under-tongue or forehead (or rectal or armpit) readings are going to be different even when taken simultaneously. Ear is typically a degree or so higher than oral. You could bring your home thermometer in to your next doctor's appointment and compare.
posted by beagle at 9:00 AM on February 10, 2022 [3 favorites]

Best answer: Have you taken your home thermometers to the appointment and see what you get there? I often read low at doctor's offices and assume it's because it's usually freezing-ass cold there, plus I'm likely anxious in a way that makes me run a little cold.
posted by Lyn Never at 9:02 AM on February 10, 2022 [14 favorites]

If you want, you can take your thermometers in there with you, use multiple thermometers at around the same time, and ask them for their comments.

Your question does say that the doctor's thermometer gave your expected reading on at least two occasions. Is it impossible to infer that your symptoms simply come and go?

If you're trying to somehow build a case against oral thermometers, I don't think that's going to work.
posted by JimN2TAW at 9:03 AM on February 10, 2022

Best answer: My ear thermometer reads a degree high all the time. It reads normally on my partner. My guess is that his ear is a different shape than mine. I would compare to an oral thermometer to see if it reads there high as well.
posted by Kalmya at 9:16 AM on February 10, 2022 [1 favorite]

Best answer: I am very distrustful of doctor office under-the-tongue thermometers. To get a good reading, they must come into thermal equilibrium with your mouth, but the staff usually only leave it there for a few seconds. My family thinks I'm crazy for using an under the tongue thermometer but letting it sit for at least ten minutes... but that's how long it takes to get an accurate reading! Particularly if you have only a slightly elevated temperature.

I agree with others, bring in your home thermometer and show them.

The infrared thermometers might be better, but forehead temperature will be lower than core temperature.

Also, my normal temperature is often low-97F in the daytime. Try convincing a doctor that you have an elevated temperature because it's at or near 98.6F (the "average over all humans over all times").
posted by pjenks at 9:21 AM on February 10, 2022 [2 favorites]

Nthing that where you place the thermometer will make a marked difference. Basically, one cannot usefully compare readings made in ear with below tongue, or elsewhere. Only ear and ear, or under tongue with under tongue. Source: my son's pediatrician.
Also, for me blood pressure makes a difference, but that is only a personal observation.
posted by 15L06 at 9:39 AM on February 10, 2022

Somewhat anecdotal, but I had a friend doing a project that involved taking a temperature as a datapoint, and noticed weird discrepancies. Evidently infrared thermometers can be affected by electro-magnetic interference.
posted by frecklefaerie at 9:40 AM on February 10, 2022 [1 favorite]

Best answer: If you’re slightly nervous at the doctor’s office, your body may be pulling your blood into your trunk as a mild stress response (vaso-constriction) and thus slightly lowering the temp of your body nearer the surface, including mouth.
posted by nouvelle-personne at 9:53 AM on February 10, 2022 [4 favorites]

Best answer: I consistently run about about a degree lower than the other three people in my household, whether it's via forehead, ear, or oral thermometer. It's gone on for years. It's very noticeable to me when I'm running even a low-grade fever, which puts me at or just a few tenths of a degree of that obnoxious average. I tend to hit the burning up/chills cycle at about 100.

There was an abrupt change when I acquired Covid the first time. I was (like I always am) sick for much longer than the rest of my household, and even once the really high fever settled down, I had intermittent temperature spikes for weeks. It's still happening, even after being fully vaccinated and boosted. After the shots, it would settle down to less frequently than previous. But after this last round of Covid (late-Dec to mid-Jan), it hasn't really stopped for more than a day or two at a time.

And it's incredibly aggravating, because no one takes it seriously, despite it corresponding to how well - or not - I happen to be feeling at any given time.
posted by stormyteal at 9:54 AM on February 10, 2022 [6 favorites]

To get a good reading, they must come into thermal equilibrium with your mouth, but the staff usually only leave it there for a few seconds. My family thinks I'm crazy for using an under the tongue thermometer but letting it sit for at least ten minutes... but that's how long it takes to get an accurate reading!

This isn't true for predictive thermometers, which have an algorithm that uses the second-to-second change in sensed temperature to report the temperature at which that curve will flatten. I'd guess that doctors' offices that only wait a few seconds are using predictive thermometers.
posted by daisyace at 5:25 PM on February 10, 2022 [3 favorites]

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