CLL Support Association
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Ear Thermometers

My Doctor told me that the electronic thermometer I recently purchased will be unreliable and at least a degree out - ( It's an under arm, under tongue one - Although not necessarily in that order 😆) He recommends an Ear Thermometer - So back to the drawing board, or rather Google and Amazon to do some research and more importantly read some reviews ! What a mine field ! Anyway I'm still none the wiser ? Therefore any recommendations would be gratefully received as quite frankly who better to ask than this forum ! Kindest Regards Juliette x

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I bought an ear thermometer when I started treatment. It's very accurate if used correctly. Simple to use and long battery life. I took mine in to a medical appointment just to compare the docs and mine. Extremely close.


Never thought of that re comparing notes with Doc etc - Good idea !


Hi Juliette,

I use an infrared thermometer that scans your forehead. It is simple to use and can record a number of previous readings. There is no contact with the skin so very hygienic and the digital display can be switched between Celsius and Fahrenheit. Like Devonrr I too took my thermometer along with me to a GP’s appointment to compare and they were within .2 degrees so I was happy with its accuracy. Another useful feature is a mode switch which allows you to measure either body temperature or the temperature of other objects like the room you are in or the cat perhaps! Sadly the actual model I have is no longer available but there is a model that supersedes it which looks very similar. The model is manufactured by Meyoung (Model no: JT-IT-WH I believe) and is available on Amazon.

Best wishes

Kevin – Essex, UK


That's interesting Foggymind - Especially the mode switch - Although I'm sure my cat would pack her bags if I ever attempted to take hers 😆 Thanks though will look it up !

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I recently bought a very similar featured model to Kevin's. I too checked it against the thermometer used to monitor my temperature when I'm having IVIG infusions. It read about a degree cooler than the hospital thermometer, which relied on skin contact with my forehead/neck.* What matters is what's normal for you and the degree of difference when you feel unwell.


* The infrared thermometer actually measures your skin temperature via infrared radiation and importantly includes a correction factor to give you an indicative core temperature.


i use an ear thermometer and have for years. i give them as gifts to new parents. They aren't cheap but very easy to use and have had no trouble with accuracy.

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What Neil says is spot on. It does not matter how your thermometer compares with the medics' versions. It is up to you to know what is your 'normal' temperature reading with yours so that you are aware of when your temperature has increased. I tell my doctors etc that my temperature has gone up 2 degrees from its normal baseline.

The same applies to weighing scales. Use the same ones regularly to spot weight loss or gain.

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Ear thermometer 👌🏻 I normally take two measures and the second is normally slightly higher! Some nurses don't put it in your ear properly. Beware.

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I had one for my cats. They didn't like it much and it was really hard to get the "sweet spot" when they were not happy with me.


The topic really burns me up! ;^)

This will be a long, technical reply. I'll put my recommendations first.

I would say that if you have a mercury thermometer, don't get rid of it. It's the disposal of mercury thermometers that presents the greatest risks - to the environment. A good gallinstan liquid thermometer would be my next choice. To try to avoid it getting stuck at a reading, always shake it down after use. Failing to do this even a few times may make a difference. Shaking is often hard to do when you're sick. So try the sock method:

1. Put the thermometer in a clean sock, tip of the thermometer to the toe

2. Hold the sock by the open end.

3. Move away from furniture.

4. Swing the sock in a circle for about 10 seconds.

This works for mercury, too.

For liquid thermometers, allow 5 minutes for the reading to stabilize.

For digital thermometers, battery level seems to make a huge difference. Also, keep it physically steady as possible, whether oral or infrared. Do not buy digital stick models that claim "instant" readings. Take multiple readings. Throw out the highest and lowest, and then average.

The techno stuff:

Most of the studies I've read on pubmed don't mention brands or specific models. They may not test more than 1 of the same model. A look at Amazon reviews shows that digital thermometers models vary wildly in quality - even the best ones. I think it's a scandal. People are being hurt by this. Readings are almost always low.

I tried several different models of electronic thermometers - digital stick oral and infrared forehead - plus a couple of galinstan thermometers (the newer liquid metal ones with green packaging) and compared them with my trusty mercury thermometer. 2 of the 3 digital stick models were identical models, and the 2 galinstan ones were identical models.

NONE were as reliable or repeatable as the mercury.

The galinstan ones tended to "remember" a temperature, and go no higher.

"Galinstan tends to wet and adhere to many materials, including glass, which limits its use compared to mercury. Galinstan is commercially used as a mercury replacement in thermometers due to its nontoxic properties, but the inner tube must be coated with gallium oxide to prevent the alloy from wetting the glass surface."

Even with the extra coating, they do tend to get stuck. Always shake or spin them immediately after reading.

The identical digital stick orals varied by as much as .4F from each other, and by 1.0F from a different model or at different times shortly after initial reading. The infrareds were sometimes 2.0F off compared to mercury. I also compared several to my doctor's electronic thermometer while at the doctor. The best I saw had .6F differences. The big thing is that the readings were not repeatable. What good is a decimal point of the reading changes in three times in 5 minutes.

I like electronics, and I used to work in a calibration lab in the military. So I started looking to build one myself. Most of the thermistors - the component that actually changes with temperature - have fairly broad ratings for repeatability and sensitivity. The thermistor has to be sampled by a small microprocessor a number of times. The processor has to be smart enough to throw away spiky samples caused by electrical noise or patient movement. They must also measure and average over a specific period to assure that the thermistor has gotten warm (or cool) enough. The electronic reference voltage circuit needs to be stable. Since cost is usually a factor, the engineers do much in the processor to correct the linearity of the signals instead of using better components. Cost is a factor even in software and processor, because marketing wants speed, but accuracy wants the opposite.

The doctor's thermometer has the ability to be calibrated. None of the consumer ones I tested a couple of years ago had that feature. I spoke to a medical technician who said that they do not actually calibrate the hospital thermometers, because the temperature standard setup was too expensive for the hospital lab to buy. I am 21st century sad to hear this.

My conclusion is that manufactures that have speed of measurement as their goal produce shoddy products. Look for ones with a longer measurement time. I may revisit this again someday if I start getting fevers again.

In my case, my temp is almost always below "normal", except after I exercise. temperature varies widely throughout the body.

Doctors and nurses who think that fever is a good sign of an infection, or who do not correct for the time of day are simply ignorant. Morning temps are almost always lower, even by as much as degree or more. This is no secret.

But the medical community in the U.S. has not agreed on a conversion scale, so they persist using the fixed scale with a fairly broad range instead. My GP clinic uses the 99.9F figure all day.

Many infections are sub-acute, yet have a significant impact on the body, but no fever. Chronic infections almost never cause fever - because they cannot stimulate the immune system to respond.

Fever is indeed usually a sign of an acute infection - usually a variant of a microbe you have not been infected by before. Fever can also be a sign of over-active parts of the immune system - which can be some of us with CLL.

So if you do have a fever, you are sicker than usual. But if you don't have a fever, you may still be sick with an infection. Fever by itself is not something you should fight unless it is extremely high. Even slightly elevated oral or rectal temperature indicates your body is fighting microbes - it's part of our natural response.


Quick note of thanks SeymourB for such a detailed and interesting response ... Not had chance to click through the links yet but will certainly be having a read. Love the sock advice ! There certainly appears to be a gap in the market given the unreliability of some of these consumer products -

"... build one myself"

A 'Seymour B' Version 1.0 sounds like a great project ! A product born out of personal experiences and coupled with a practical requirement are always the best !

Thank you once again, some food for thought here and a really great reference post 🙋🏻

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Juliette -

I got as far as selecting the parts, but it turned out to need a lot more in software testing than hardware, so I decided to stick with my mercury and galinstan ones.

To pick just good hardware is expensive:

Meanwhile, I'll continue watching the reviews from time to time to see if any infrared ones stand out.

Somewhere on the web there's got to be an engineer with a loved one who has fevers that disappear by the time they get to the doctor.


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