Cheap smartwatches with CGM… What do we think?

For some reason, (I couldn’t possibly imagine what!) Cheap smartwatches with non-invasive CGM started popping up in my social feeds, making all sorts of claims of greatness.

Given the price, I thought we might as well see how well they work…

First up is this one, the KS01, from somewhere in China.

At less than £25, it was obviously a bargain, and a worthy experiment.

So what does it do?

Features:

• Blood pressure
• Glucose monitoring
• Blood oxygen
• Heart rate
• Pedometer
• Body temperature

Clearly, this must be a very efficient little device. What I will say for it is that the battery lasts a long time, and the pedometer is reasonable.

I’ve never managed to get a heart rate reading from it, nor a blood oxygen output.

The body temperature sensing seems to be sensible, and the pedometer matched my other step counters, or near enough.

But the blood pressure readings are, well, questionable really, when compared to a proper home blood pressure reader. They certainly aren’t useable for anything other than a bit of fun.

But what of the glucose? Well that’s what we’re here to talk about…

Non-invasive glucose monitoring

This little watch takes a reading every ten minutes, and stores them on your phone in a way that’s impossible to export. The app looks like the picture below.

But there’s an important thing to highlight. It requires that you specify your fasting glucose (from a fingerprick) which it uses as a datum about which it takes your readings.

In this image, I’ve set that value to 4 mmol/l (which is well below my 5.5mmol/l target value). When you compare it to a Dexcom G6 from the same day, you can see a fair amount of difference…

While the watch won’t show the overnight compression lows, the variability of the readings is noticeably different.

A comparison on actual values

The next plot takes a day with the watch normalised to my target value, and then Dexcom data points aligned to the watch ones. The Dexcom points were the nearest point by minutes to the watch readings.

It’s pretty clear from the overlay of the two graphs that the sensors on the watch are neither accurate or responsive.

In many ways, there is no point in them.

To be fair to the device, the sellers don’t claim it has a medical use, and describes them as “consumer product” sensors, but still…

They are of little use to anyone.

The takeaways are clear

The glucose sensing in this particular watch is of little use to anyone. It doesn’t reflect reality. I suspect, if you were non-diabetic, you’d see a nice flat line, but who really knows? It might still be lumpy. At random times.

And that’s really the takeaway. The sensors in this thing don’t really do anything useful. They create some ups and downs, but don’t give you any trustworthy information about what might be happening to your levels.

But for less than £25, what did you expect?