What is a fever, anyway?
March 22, 2020 7:02 PM   Subscribe

YANMD, etc., but I never learned this from my mom growing up and it's hard to parse the conventional wisdom now that we're in the era of Covid-19, but: how does one factor in a fever if they feel "normal," and is there a way to measure a fever's severity apart from the thermometer read-out?

My temperature, over the past 24 hours, has measured wildly all over the place, everywhere from 102.0 to 96.5. A moment ago, I measured it as 102.1; one minute after that it was 101.1; twelve minutes after that it was 97.5!! I went for a two-mile walk this afternoon and it was 96.6 when I got home. What do I make of this?!?

My physician/aunt has ordered me to get a flu test and quarantine inside my home (which I have done, and the rest of my family is staying home also--we've been self-isolating since last Sunday). So I am keeping a distance and sanitizing everything I touch. But I also feel FINE, with the only symptom being anxiety (normal) and a very occasional light tickle, like I need to clear my throat. But I'm not accustomed to the concept of a fever, so I don't know how to interpret these numbers and when to take Tylenol for fever reduction.

We are using the Braun infrared forehead thermometer, and I don't know if there are known accuracy issues with that model or what, but there are no other thermometers available for sale in my area, so it's what we're sticking with for now.

I'm in my mid-30s, female, and in pretty good health (no reason to be concerned about underlying conditions). Any advice or perspective is welcome, and thank you in advance!
posted by witchen to Health & Fitness (16 answers total) 2 users marked this as a favorite
Infrared thermometers are not especially accurate, definitely not the consumer grade ones, and if you measured right after coming in from your walk, you're not using the thermometer properly.
posted by inkyz at 7:14 PM on March 22 [6 favorites]

There's something wrong with your thermometer or your method if you're measuring 102 and 97.5 within a span of 13 minutes.

In general, if you're an adult and you feel fine, you don't have a fever. You'll feel quite sick if you have a fever worth worrying about. You would not be taking two miles walks. You would feel at least somewhat hotter and weaker than usual.

Little kids more often have slight temperature elevations that aren't worrisome, but in general even they will look and feel sick and weak if they're feverish.

When you do have a fever, the standard practice is to take Tylenol if the fever is making you uncomfortable. It doesn't always, if you can just lie down and be hot and weak in peace. For little kids it's different, you need to make sure they don't get dangerously feverish.
posted by fingersandtoes at 7:14 PM on March 22 [19 favorites]

Something is very likely not right with that thermometer. In my experience, if you have a fever of 102, you would absolutely know something was wrong. You'd feel very hot, the air would feel very cold - you'd likely be shivering if you weren't under a blanket, and you'd be sweating. You'd also probably feel loopy - maybe a bit confused or silly - and you might be, not dizzy exactly, but the room might feel a little swimmy. Anybody that touched your forehead or your neck would notice that you feel very warm, and you'd probably be very flushed.

That said (sorry) I have read accounts of flashes of high fever with Covid-19 that seem to come down pretty quickly. But those fevers come down in a matter of hours, not minutes.
posted by pazazygeek at 7:24 PM on March 22 [6 favorites]

I have a two year old, and have thus come into possession of one mercury thermometer, three cheap oral digital thermometers, and two forehead thermometers over the last three years. I checked them all for accuracy when covid kicked off.

The mercury and digital oral thermometers all read within 0.2 degrees of each other. The forehead thermometers disagree with themselves by 2 degrees between consecutive readings, and do not center around the actual temperature.

I think your thermometer is simply wrong, and you should ask around to borrow an oral thermometer.
posted by john hadron collider at 7:38 PM on March 22 [7 favorites]

I've seen really high variability with consumer grade forehead thermometers. I would not place much faith in those measurements. Every time you take one, take several, and keep measuring until you get some agreement... and when you have a chance get a thermometer that goes in your mouth.
posted by potrzebie at 8:35 PM on March 22

Slightly oddball suggestion — i haven’t been able to find a medical thermometer to purchase so I’ve been using my digital meat thermometer until I do. It doesn’t have the same precision but i’m pretty confident it’s calibrated right (when exposed to air it has the correct room temp) and if i put the probe under my tongue it’s been consistently 98 or 99, which is good enough for me. I’ll worry if it hits 100 or 101. Any chance you have one in your kitchen you could use a a second opinion to your current thermometer?
posted by cgg at 9:05 PM on March 22 [4 favorites]

I just threw away a thermometer for giving readings like that. I compared it against our other human thermometer and our instant-read meat thermometer and, yeah, the thing was just failing.
posted by palmcorder_yajna at 11:30 PM on March 22

The ones that do forehead temperature readings aren't great. You need very good technique to get an accurate reading, and you need to press pretty hard in my experience. I always do multiple readings.

Real fevers cause your body to be uncomfortable. Your body is using more energy than normal to heat you up, you will feel exhausted. You will feel uncomfortable. You willhave sweats and chills. Sometimes especially with higher fevers you will get confusion symptoms. The older you are the more likely infections cause confusion with or without the fever component .

If you have anxiety you really want the reliability and consistency instead of ease of use. That way you can be sure. There are plenty of cheap digital oral thermometers that will do that for you. If you are worried about germs, you can buy little covers.
posted by AlexiaSky at 1:39 AM on March 23 [3 favorites]

Oh, and when you have a fever you will likely know without the thermometer. I hadn't run one for years and ran one over president's day weekend. I definitely knew. I was miserable. There was no questioning about it. I woke up and was like"I have a fever for real for real" and yup I did.
posted by AlexiaSky at 1:43 AM on March 23 [1 favorite]

I hadn't had a fever in a really long time, and didn't own a thermometer my entire adult life. I got sick in late 2019 and was asked by a couple doctors if I had a fever at any point in the sickness, and I confessed that I didn't think so but also I didn't know since I didn't own a thermometer. I bought a thermometer after I got better so I could answer more knowledgeably in the future. I got a pretty nasty cold in mid-February but it never even crossed my mind to use the thermometer then. I'd been living without a thermometer for over a decade, so it isn't normal for me to think to use one.

Then in early March right before COVID-19 really arrived in the US, I got sick again and I could tell that I had a fever. I was quite cold when everyone else was fine - as in, I turned my house up four degrees more than usual and was still cuddling under an electric blanket and shivering. The realization that I had a fever meant that I finally opened my new thermometer, and sure enough, it confirmed it and gave me a number to go off of, which is good and helpful. However, I didn't need the thermometer to tell me that I had some level of fever; rather, I knew I had a fever which led me to get out the thermometer. Pre-fever, I hadn't had one in so long I didn't know what it felt like. Post-fever, it was obvious what a fever feels like. (Turns out I had the flu (tested positive on swab test).)

I think your thermometer is broken.
posted by vegartanipla at 1:44 AM on March 23

I agree it's the thermometer. Our forehead thermometer needs multiple takes and has a weird child setting that will read low for adults and high for children SOMEHOW by witchcraft, and is just annoying. However, it's very fast and only touches forehead so I can use it among the household without worries of spit swapping. If you can get individual labelled oral thermometers so you don't have to vigorously disinfect to change people, just rinse in hot water/wipe between checks, I'd do that.

I know I have a fever when I ache and my eyes feel "boiled dry", a friend's evocative description. For my kids, it's their level of activity together with temperature. 37.9 and running around, meh. 37.9 and too tired to watch youtube, panadol time.
posted by dorothyisunderwood at 1:57 AM on March 23 [1 favorite]

I also agree that your thermometer doesn't sound reliable, but to counter all the "you'll definitely know if you have a fever" people, I've had a few experiences where this wasn't reliably true.

I was accused of lying by a doctor about five years ago when I had an ear infection and claimed I didn't have a fever (I felt fine systemically, apart from the pain in my ear), but when he took my temperature I apparently did have a fever.

Another time, when I definitely felt like I had a fever (aching joint pain moving around my body, alternating between chills and getting way too hot), my temperature only barely spiked over 37.5/99.5 at the peak of the fever symptoms, even though I felt terrible all day and it got bad enough later in the evening that I passed out twice after I went into a hot room.

Since then I've figured out that my body temperature runs on the cold end of the spectrum of normal temperatures (I've been taking it daily this week as some coworkers have had COVID-19 symptoms and it's been consistently 36.4-36.8, so I guess low 37s are higher than average for me even if they're normal for other people), but given that in the past I've had fever temperatures without any fever symptoms AND fever symptoms with a temperature that fell short of the official fever range, I'm inclined to think that there's an element of ¯\_(ツ)_/¯ about the whole thing.
posted by terretu at 3:00 AM on March 23 [3 favorites]

I have a few oral thermometers and I'm always worried that they aren't working right, so if someone in the house seems feverish but it's not confirmed by the thermometer, I'll check everyone else's temperature too as a comparison. It helps that there are 5 of us here, though.
posted by cabingirl at 6:23 AM on March 23

Yeah, I think it's your thermometer. I have a cheapo digital one and have been taking my temperature every day for the past couple of weeks. My normal temperature is in the low range, 96-97, so 99 is for me a fever. The advantage of taking it every day is that you get a sense of your baseline.
posted by mareli at 7:58 AM on March 23

We have a Braun forehead model that was repeatedly reading 105.8-107.5 on my 5 yr old over a 10 minute period. I checked his axillary and oral temperatures on a hunch before progressing to an emergency response since kidlet was acting 100% fine beyond looking a little flushed. The oral and axillary temps were 101-101.5 consistently. This was not the first time it was unreliable but it was the scariest, so I don't use it anymore.

If there is any way you can acquire a different thermometer to set your mind at ease, I'd recommend it. One place to check if the first aid area is sold out would be the family planning area - an thermometer intended for checking BBT (basal body temperature, which folks chart to track ovulation) will perform just fine as an oral thermometer IME.
posted by Ann Telope at 7:41 PM on March 23

If it's not a VeraTemp or other clinical-grade non-contact thermometer ($450 and up), with recent calibration, I'd not trust it much.
posted by bz at 10:22 AM on March 24

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