Keto Mojo vs Freestyle libre 2 (results)

(Fabian ) #1

Hi everyone,

I’d never checked my glucose levels before going on keto for about 8 weeks.
While on keto, I checked regularly with my Keto Mojo and got a fasting glucose of about 77/80 most mornings,
I then decided to increase my carbs (maybe 100 gr) and did 2 meals a day (IF) and got similar fasting glucose.
3 days a go I went off the diet and started to eat between meals a bit, more carbs… and yesterday I went a bit out of control , eating cookies, chocolate spread… (maybe 200 carbs or more, I’m not sure) so I thought it was a good time to test the Freestyle LIbre 2 I had bought a few weeks before.

This morning (ater fasting for about 11 hours) the glucose readings were around 120 (max 123) , according to Google, that’s pre diabetic…
So I immediately checked with my keto Mojo that read 98 mg / dl…

That’s a 25 mg difference! Which one is more likely to be correct?
And if the Freestyle Libre is correct, should I worry or put it down to the crazy day I had yesterday?

Many thanks!

(Bob M) #2

It’s hard to know. When I had my Free Style Libre, I only got two data points with an official test (blood draw at a facility). One was spot on, the other was not. This was while I did a Kraft test, though, so there’s a delay between blood and interstitial fluid.

At the same time, I had used my meter (it was the most “accurate” one at the time), and got basically the same results: One was correct, one was not.

(Fabian ) #3

The annoying thing is that I’ve paid more than 100 euros (the 2 devices) to get a precise answer to my doubts and at the end of day, one tells me I’m pre diabetic and the other one that I’m fine…
It could even turn out to be dangerous if you rely on the results of the device that got it wrong…

Has anyone else had bid differences between the 2 devices? Which one tends to be more accurate?

(GINA ) #4

One thing to keep in mind is that a CGM isn’t measuring blood glucose, it is measuring glucose in the interstitial fluid under your skin, which ‘lags’ 15-30 minutes behind blood glucose. So if your blood sugar is on the way up or down, the CGM will seem off. You could do a blood test, then check your CGM 20 minutes later.

I have used a Libre with a regular tester (not Keto Mojo, but I don’t remember the brand) and was always very close (when accounting for the delay after eating). Fasting it matched a blood draw at a lab too.

Having said all that, I have noticed the readings are wonky for the first few hours after I put one one (even past the time the instructions say to wait). By the next day they settle in and seem accurate though.


Well… since you asked

Here are my results over about 6 2-week periods.

If you throw out some outliers, it seems the CGM is less sensitive than ketoMojo. Per manufacturer, the CGM measurements are 5 minutes after the keto mojo.
In the following graph some outliers are removed and the dashed lines are pul/minus 10%
It may be a bit deceptive. The solid red line is not a best fit but y=x, perfect agreement.

Here is the (lousy) fit showing a much different slope


(Bob M) #6

I always used the CGM so show curves and get other data. What happens when you eat high carb? Or protein?

I found the pinprick meters way too variable to get data like that, and also you have to prick yourself a lot to get an accurate result. For example, all the websites tell you to take a blood sample 1-2 hours after eating, which is what I did. Then I got my CGM, and if I eat low carb, my blood sugar is flat. If I eat high carb, my blood sugar is up and down in 1 hour.


I have a keto mojo. If I get a surprising glucose reading, I immediately test again. If the second result disagrees wildly (more than 10 points), I take a third test and throw out whichever of the first two seems to be an outlier. Ketone readings seem way more consistent so I rarely test those twice.

(Fabian ) #8

Thanks for the graphs, but the info goes over my head I’m afraid…
When you say the Keto Mojo is more sensitive, you mean more accurate?
Next week I happen to have a blood work scheduled in the morning, will that result be 100% accurate?

(Fabian ) #9

Thank you, I will give it another day and see what happens…

In my case both readings were in the morning after a fast of more than 11 hours, so the difference between blood glucose and the glucose in the interstitial fluid would be ireelevant, I guess.
25 mg sounds like a big difference to me.

(Bob M) #10

No, but it will be very close to the real number. Pinprick meters are considered to be 100% accurate when they are within 15% of the real value. Way back when I looked into this, the one I bought (Bayer Contour Next) was the only one that actually met that standard. And that’s at 15% error, so if you really have a blood sugar of 100, anywhere between 85 and 115 is considered to be accurate.


(Fabian ) #11

Thank you

I will compare my bloodwork results with the 2 devices…

For the Keto Mojo, if there are inaccuracies, do they come from the device itself or the glucose strips (that may vary from batch to batch?
Is the device consistent in its accuracies or is it just unreliable /inconsistent?

(Bob M) #12

Good questions, which I can’t answer.

At one time, I was comparing results from my Bayer Contour Next Ez and my European Free Style Libre CGM. After the time, it’s the Bayer’s readings, then the European CGM, then I converted that value to US units. The European CGM tends to read low (edit: or the Bayer reads high):

Edit2: At the time, I didn’t know about the delay with the CGM, so maybe I would have offset the times a bit (take the CGM 15 minutes later, for instance). But a lot of these are “fasting” ones anyway, so they should be the same.

(Jane) #13

I wore a Freestyle Libre for about 10 days (quit on me early) and it consistently read 20 units below my KetoMojo readings and my KetoMojo numbers were what I would expect. Even taking into account the time delay.

One day I fasted all day and the Libre was still 20 below my KetoMojo all day. But it trended correctly.

(Megan) #14

Hi Fabian, regardless of which is correct or not, both readings are telling you to keep your carbs low. Best case scenerio is the reading from the Keto Mojo is correct, but 98 is quite a bit higher than your previous consistent readings of 77-80.

(Kate) #15

The Freestyle reads the glucose in the interstitial fluid as opposed to the blood. I have used a freestyle and a blood glucose meter and I can have a different of 2 - 2.5 mmol at the same time. Having said that the difference for me may be because I have Lipedema in my arms.

(Fabian ) #16

Interesting, the opposite of what happened to me, I hope…

Talking about fasting, I was wondering, when we fast for several days relying on our fat reserves, do we eventually all get to the same blood sugar levels or it depends on wether your are type 2 diabetic, obese, your age…?

(May the blessing of bacon be always with you) #17

It depends on far too many factors to predict. Your activity and stress levels are part of it, certainly.

George Cahill’s fasting subjects produced a fair amount of ketones, enough that he was able to drive their glucose levels down, artificially, to the point where people without such high ketone levels would have been in a coma or dead, but they remained just fine. As Dr. Phinney points out, today you’d lose your funding (or worse) for trying a stunt like that, and it was considered unethical even back then (the 1960’s), but it is useful information nonetheless.