Frequent Blood Sugar Measurement

I’m experimenting with blood sugar measurement using the Freestyle Libre system. Just one day so far. The sensor is a small patch with a filament that goes just a few millimeters into the skin. It is easy to apply.

Data is stored in the sensor until it is loaded onto a small reader that you wave over the top of the patch. I’m using a Freestyle Libre Pro unit prescribed for me by my doctor, because the regular Freestyle Libre is not available in the US. This means that the data is inconveniently “blinded” on the reader - you cannot see the data until you plug the reader into your computer, set up a “patient ID” and download the data. However, once you take these steps, it is in a logical format and easy to work with. I’ve pasted a sample of my data, with notes I added to my spreadsheet after.

I’m interested if anybody else is using this too.

ID 	    Time	  	  Glucose (mg/dL)	Notes
6607	2017/05/01 11:01	0	1       fasting
6608	2017/05/01 11:16	0	116	    fasting - lightheaded
6609	2017/05/01 11:31	0	113	    high protein meal
6610	2017/05/01 11:46	0	105	
6611	2017/05/01 12:01	0	105	
6612	2017/05/01 12:16	0	101	
6613	2017/05/01 12:31	0	99	
6614	2017/05/01 12:46	0	116	
6615	2017/05/01 13:01	0	126	    Espresso
6616	2017/05/01 13:16	0	124	
6617	2017/05/01 13:31	0	115	
6618	2017/05/01 13:46	0	105	
6619	2017/05/01 14:01	0	100	
6620	2017/05/01 14:16	0	102	
6621	2017/05/01 14:31	0	109	
6622	2017/05/01 14:46	0	111	
6623	2017/05/01 15:01	0	111	
6624	2017/05/01 15:16	0	114	
6625	2017/05/01 15:31	0	125	     OJ, honey nuts on SW Air
6626	2017/05/01 15:46	0	135	
6627	2017/05/01 16:01	0	128	
6628	2017/05/01 16:16	0	111	
6629	2017/05/01 16:31	0	109	
6828	2017/05/01 16:46	0	116	
6829	2017/05/01 17:01	0	112	
6830	2017/05/01 17:16	0	106	
6831	2017/05/01 17:31	0	102	
6832	2017/05/01 17:46	0	108	
6833	2017/05/01 18:01	0	110	
6834	2017/05/01 18:16	0	105	
6835	2017/05/01 18:31	0	98	
6836	2017/05/01 18:46	0	96	
6837	2017/05/01 19:01	0	97	   Dinner
6838	2017/05/01 19:16	0	100	
6839	2017/05/01 19:31	0	103	
6840	2017/05/01 19:46	0	104	
6841	2017/05/01 20:01	0	112	   Dessert
6842	2017/05/01 20:16	0	130	
6843	2017/05/01 20:31	0	146	
6844	2017/05/01 20:46	0	149	
6942	2017/05/01 21:01	0	128

Hey Gary,

Yes, I have been wearing the Freestyle Libre for a few weeks and have also worn a Dexcom sensor for a month as well just out of interest and curiosity. As a physician, after wearing these and seeing the insights, I am now convinced that wearing Continuous Glucose Monitors should be a requirement for every medical student to wear.

In order to get the raw data off the device, we just had a colleague overseas download the software (only available from a European IP.) Using that data, I have actually been building a presentation for QS combining what we know about physiology with results from the Libre. It should definitely help people who want to self-diagnose insulin resistance (Diabetes or Pre-diabetes) or maximally impact blood sugars to facilitate weight loss.

If you are interested, it could be great to chat, compare results, and swap insights.


This is a great thread. I intended to purchase a Libre Pro. May I ask where you got yours (both to Gary and Praxiteles)? I’ve got friends in EU locations to get that extra software.

eBay. Be sure you get an English one

@jackpark - I had my friendly physician prescribe me one to investigate my metabolism. I’m investigating episodes of lightheadedness and sleepiness that come on very suddenly, thinking these might be visible in blood sugar patterns, allowing me to get better ideas about how to prevent them.

@praxiteles - I would love to compare experiences. My suggestion is that we do this here in the public thread, unless there is sensitive material you’d rather not share. It’s great to have a record of what we are learning that others can reference.

I’m using the Freestyle Libre Pro software that came with the reader. Freestyle Libre Pro is available by prescription in the US, but the expectation is that the doctor will keep the reader, and the patient will come into the office to have the sensor data read and reports generated. But in this case the doctor let me take the reader home, so that I could use the data myself, and then we will discuss it when we are together.

Of course I’d prefer if the connection between the sensor and my spreadsheet were more direct - it takes a fiddly, multi-stage process to get it sorted. But I’m very happy to be able the get it, and the sensor is quite straightforward and has survived 4 showers by this point with no harm done.

It will take a few more days, at least, to just get a baseline sense of where I’m at, and after that I might try running some simple experiments, perhaps involving time of eating.

Are you saying Libre Pro? All I can find there is the sensor for pro. I find Freestyle Libre (not pro) there. Hard to tell about expiration date on sensors. My friendly physician says I don’t qualify for an rx for a libre pro, and besides, that product doesn’t show up in her records.

@jackpark Here is the link to give your physician: I don’t think there is any restriction on giving it to patients, however it was not covered by my insurance so I had to pay for it outright.

The FreeStyle Libre is approved in Europe for patients. The FDA hasn’t approved it yet in the U.S.

The Libre Pro is the U.S. version which is only approved for physicians. I just went through the process to become a physician who can distribute the sensors. Abbott only approves us to get one Reader so patients have to come to us to get the results as the FDA hasn’t approved its use by patients without supervision. Gary’s doc broke Abbott’s rules a little bit - but then we all tend to break rules if we can help patients. It might be partially overlooked because Gary isn’t actually managing diabetes with it. It is hard to say. The Abbott sales folks said that they are watching everything closely because they don’t want to jeopardize their review by the FDA and their release. For example, they refused to ship them to my home address and only would send them to a certified healthcare facility (just to ensure they don’t end up in patient’s hands until proven safe.)

@praxiteles That clarifies things, thank you. I’m currently exploring a DIY system for reading the data off the sensors, brought to us by the “we are not waiting” heroes of the Nightscout project. I know that @Jolly has posted about this system on the forum already, so I’m optimistic.

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A question I’ve been asked: How does Freestyle Libre do against glucometer readings? Over two years ago there was some deep discussion of this on the diabetes blog “Everyday Ups and Downs.” The verdict was “pretty well, though with significant exceptions for some users.” You can read the results below.

Abbott Freestyle Libre results vs BG meter - Review part 2

One clever test that suggested in the discussion was putting a sensor on both arms to test reliability. I may do this. Another interesting issue mentioned is that the Libre, which estimates blood glucose levels from sensing glucose in interstitial fluid, has a time delay. I don’t think this time delay is long enough to hurt the analysis I’d like to do (5-10 minutes is what’s guessed in the comments), but if it’s longer that would be important.

As far as accuracy goes, perhaps most significantly, the Libre is being positioned as a replacement for finger sticks. According to the documentation, finger sticks are only needed when glucose levels are changing fast and so your interstitial fluids haven’t equilibrated.

Here is the accuracy according to their reports:

"…The FreeStyle Libre system is clinically proven to be accurate, stable and consistent over 14 days compared to blood glucose testing without the need for finger prick calibration

In a clinical study, the FreeStyle Libre system achieved 11.4% Mean Absolute Relative Difference (MARD) compared to blood glucose testing (2)
99.7% of glucose results fall within Zone A and Zone B of the Consensus Error Grid2
The measurement errors associated with these zones have no effect on clinical action and little or no effect on clinical outcomes (3)
On the first day of wear, 99.5% of glucose readings fall within Zone A and Zone B of the Consensus Error Grid2…"

@Praxiteles @Agaricus Thus far, my HMO physician is refusing to give an rx. I’m approaching a friend who is an M.D. to see what I can come up with.
On accuracy, my plan has been to simply record a cluster of readings before eating, average those, and then normalize clusters following eating after that, thus plotting deviation from the beginning reading. I’m less concerned with absolute values, more concerned with the shape of the curve.
I have an intention to put up a website as part of my “knowledge garden” work so that many participants can conduct similar experiments and we can all learn from each other.
Since I don’t expect reimbursement, what, say in round numbers, does Pro cost when purchased by the online seller?


Huge question: when you get a Libre Pro, who puts the sensor on you? You, or a physician?

Great thread! Just out of curiosity, is there any benefit to tracking glucose with this for non-diabetic people?

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You can place the sensor yourself ( though I usually have someone do it so they can place it a little bit on the back side of the arm so it doesn’t interfere if you sleep on your side.

@Invivo Yes, there are benefits to tracking glucose for non-diabetics. You can compare different foods and their effect on your blood sugar. Studies suggest blood sugars over 140 cause permanent damage to the pancreas and predispose a person to Type 2 diabetes. Additionally, blood sugars over 140 (no one knows the exact number) also seem to be “adipogenic” causing the body to accumulate fat. Using a continuous glucose monitor can help track down foods that contribute to weight gain.

Gary - Here is one thing that might be interesting to try and valuable for the community.

We could create a comparison of glucose curves across people against a standard food or beverage taken in the morning. I have insulin resistance (or some as yet undiagnosed pancreatic dysfunction) - whereas based on your blood sugars above - it appears you do not - or yours isn’t as severe. (This effort would answer that.) It could be interesting for us both to try the same food in the morning and superimpose the blood sugar responses. If we superimpose lots of different people’s curves for a particular food or beverage taken at a particular time in the morning before any other food is eaten - we can discover and help people to see where they fit on the curve and diagnose their own levels of insulin resistance. Additionally, as people improve their metabolic profile (through exercise or fasting etc.) they could see how much they improve their own insulin response curves.

If we do this, I would suggest we choose a food or beverage that has given you the highest spike yet on your blood sugar. If that sounds interesting or worthwhile, feel free to let me know.



The idea of comparison of glucose curves is exactly in line with what I hope to do. My interest lies in the shape of those curves, less in the absolute values, though absolute values (given error bands) are important. Large scale (many people, many samples, many variations) experimenting seems valuable.

@Praxiteles @Agaricus It’s looking more like I will not be so lucky to have a physician grant me an rx; large-box HMOs can be pretty sticky; if it’s true that the reader must be delivered to a clinic, that might contribute. On the chance that’s the case, there are Freestyle Libre machines at ebay (maybe elsewhere? – Amazon says out of stock) with prime issues being reader language and sensor dates, what is known about accuracy of the not Pro version of the Libre?

@Praxiteles I think this is very interesting. Let’s the two of us try it a few times and see if we can get the process into focus, then invite others to join.

One thing I haven’t yet figured out is a workflow for putting my blood sugars and food in the same chart. Right now I just take notes on my spreadsheet, but it’s not a great method. How are you doing it?

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