Tracking body temperature

I’m curious what my normal temperature range is, what the effect of seasons, food, and exercise is, and whether temperature can be an early warning sign for health issues.

So I’m looking for a device to take daily readings without too much hassle, and that is accurate enough to detect small changes.

A wearable, continuous tracker would be ideal, but apart from one device (Kindara, which isn’t available yet, and wouldn’t work for me anyway), these devices estimate core temperature from skin temperature. The accuracy of this may be good enough to estimate trends (e.g. for fertility tracking), but maybe less so for detecting unexpected, small changes?

Other devices I’ve come across:

  • Withings Thermo: Data can be exported, not sure about accuracy.
  • Kinsa QuickCare or Smart Ear: No data export (yet).
  • Vicks SmartTemp: Data can be exported via email, not sure about the accuracy (suspiciously cheap)…

Any recommendations? Advice for things to consider when taking daily readings?

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mbient labs make a wearable sensor bundle including temperature. it could probably run for more than three days without upload or recharge if all you do is record temperature. A bit flaky though. Also contact would be over plastic so ambient temperature may be measured more. On the upside its wearable with many sensors for just 100usd.

I hear the oura ring can record temperature.

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mbient labs looks interesting, but, as mentioned above, I don’t think you can use skin temperature to answer questions such as “how much does exercising on a hot day increase my core temperature”. Oura may be a bit better due to where it’s placed, but that also makes it a device I don’t want to wear during exercise…’s devices are quite small and could easily fit in an armpit. They sell things that could keep it there. I think Oura measures peripheral temperature more. That is also useful (not for fevers) so long as ambient temperature outside the body is also recorded.

I use one of these! I came to QS with this data first in mind.

I use a device called iThermonitor that measures core temperature (not skin temperature). It is made by Raiing and was designed to be used in hospitals for continuous, noninvasive core temperature monitoring, and multiple studies have demonstrated clinical accuracy. While there are lots of interesting applications in the hospital setting, as a consumer you can buy one from a reseller/licenser. The packaging varies but the device itself has a consistent design and the product name or description includes “iThermonitor” or has matching specs.

It is a small plastic sensor you keep under your armpit using an adhesive patch. It measures your temperature every 4 seconds and syncs with apple health.

I got mine under the name “FeverFrida.” I appears that it was licensed to a childcare products company, and parents are using it to monitor infant temperatures during illness so they don’t have to wake them up as often.

It is difficult to place it consistently- it does make a difference in the reading.
Having to reapply the patch so often (Although I just stick it in my bra)
The use cases it’s sold for and the study conditions don’t match the realities of regular adult life.
It seems like it has become difficult to find to purchase.

That being said, it’s fun and potentially useful data. Even if you do not place it consistently day to day, if it stays in place you may have an accurate trend for the day. I like to collect data points via oral thermometer as well from time to time to figure out what adjustment I need to make for a baseline. Personally, it always reads as lower than my oral temperature by about a degree.

I’d love to hear if others have tried this device or if you have thoughts on the difference in the oral temperature reading and core temperature reading with this device.

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@azure wrote a post some time ago that included details on tracking body temperature with iButtons:


Could be interesting to try to establish how closely my skin and oral temperature correlate, and if I can use former to calculate latter (as @ssol mentions doing)… But initially I’m not even sure if the oral temperature measurements are sensitive enough!

I placed an order for a Kinsa QuickCare last month, and supposedly it shipped today…

I have since received the Kinsa QuickCare; here are some initial impressions:

  • Taking oral readings is quick and simple. No issues syncing the readings to the app (either at the time of the reading, or later).
  • Successive readings are within 0.1°C of each other, so there’s no point averaging out multiple readings. I have to assume the device isn’t cheating :smile:
  • You can export data for the last 14 days. The format is just about parseable.
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Kinsa recommends waiting 15 minutes after eating or drinking before taking oral readings. To see for myself if that’s really necessary (or, sufficient), I took my temperature a few times after drinking hot tea, and after drinking ice water.


Looks like 15 minutes is good advice, but it can take up to an hour for everything to return to normal. Since I didn’t spit out my drinks, it’s possible that the changes that persist past the 15-minute mark do in fact reflect changes to my core temperature, rather than being measurement artifacts.


The Kinsa QuickCare Smart Digital Thermometer seems to be sold out widely.

Looks like their online shop has it in stock, at the moment…

Here are ~hourly temperature readings taken over a week (incl the median values):


This is about as expected, with lower temperatures in the morning, and higher temperatures later in the day. Much of the variance throughout the day can be explained by unsurprising things like meals, or sitting in a hot apartment… Exercise, surprisingly, appears to lower my temperature (or just the oral readings?), both indoor and outdoor.

I’ll continue to take daily readings in the morning, right after getting up. These readings have so far all been within the margin of error for the device. There isn’t an obvious (and convenient) time to capture the “high point”, which could have been interesting as well.

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Here are my daily morning temperature readings (incl deviation from the 7-day median) so far:


The 3 readings below 36.7°C all happened to be taken after sleeping outdoors. The one slightly elevated reading so far (37.1°C) didn’t correspond to anything.

Could this be due to the thermometer being colder? To rule that out, I took a few readings before and after leaving the thermometer in the freezer for a few minutes:


Looks like a cold thermometer can indeed reduce the readings by 0.1-0.3°C! So if the air temperature is well below room temperature, I should probably warm up the thermometer in my mouth for a minute or two, until I get stable readings.

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Spent another night sleeping outdoors, with the air temperature dropping to around 14°C. But no matter how much I tried to warm up the thermometer this time, readings showed a consistent 36.7°C (i.e. 0.2°C below my normal)…

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Just came across this fun review of the Withings Thermo, looks like it isn’t suitable for detecting “normal” temperature variations:

Do you think your body is just colder?

Looks like that’s the case; just wanted to rule out that the lower readings are an artefact!

Next question is whether my body is colder because I spent time in a colder environment, or because I consume fewer calories while outside…

Perhaps not surprising, but traveling across time zones affects the morning readings: -0.2°C for a full week after shifting -9h, and +0.1C above my pre-travel temperature average for almost a week after shifting back.