A better glucose monitor for hypoglycemia?
March 4, 2021 9:17 AM   Subscribe

My endocrinologist says glucose monitors, and in particular continuous glucose monitors, aren't very accurate for hypoglycemia. She also says that her awareness of the performance of these products is from about eight years ago. Are you aware of any finger prick or continuous monitor options that are better with measuring low blood sugar than others?

Note: this is for monitoring non-diabetic hypoglycemia, if that matters.
posted by 10ch to Health & Fitness (13 answers total) 3 users marked this as a favorite
I am not diabetic, and am using a Freestyle Libre sensor to monitor my low blood sugar. It is the first time I've used and worn a continuous glucose monitor so I cannot speak to its efficacy over others.

Having neve done finger pricks either, I've been pleased with the simple and straightforward nature of the Freestyle Libre. I don't use an external metre, but rather an app called LibreLink on my iPhone. I can share the logbook with my dietician through an iOS app called LibreLinkUp.

I learned a lot from watching non-experts on YouTube share their experience. I set an alarm on my phone for :50 every hour to do a quick scan, taking advantage of a habit stack to get up, stretch, and get a few steps in.

Feel free to MeMail me if you have questions. I'll do my best to help.
posted by nathaole at 10:14 AM on March 4, 2021

I also use the Freestyle Libre, and I have been very happy with it. The reader has a built-in glucose monitor, so if you get an unusually low or high reading, it is easy to do a quick finger stick to double check (and the reader actually prompts you to do so via a "blood droplet" icon on the screen.)

You can also use your phone as a reader, but if so you would want to have a separate finger-stick type monitor to do the double check. I personally like the reader and it makes it convenient to have the option to use it as a glucose meter so you don't have to carry a separate kit.
posted by Serene Empress Dork at 10:47 AM on March 4, 2021

My indirect experience (via a relative) is that Dexcom G6 is pretty accurate. Certainly better than something from 8 years ago. They also tried the Freestyle Libre, and preferred the Dexcom because it's constantly monitoring and can give alerts on configurable criteria, rather than requiring a proactive scan like Freestyle. This is especially useful if there is risk of overnight hypoglycemia (assuming you don't want to wake up in the middle of the night and periodically check). The advantage of the Freestyle is that the physical sensor on your body is smaller and less obtrusive.
posted by primethyme at 10:55 AM on March 4, 2021

I should add, for diabetics at least, hypoglycemia is a potential medical emergency. So it is important that these devices detect it and alert on it. They do not want to mess around with this. People can die. It seems that (again, second-hand) it's more likely to give a false positive than a false negative on hypoglycemia. I don't know which side you want or need to err on. But from what I've seen, it's pretty unlikely to miss a hypo event, but it might sometimes warn of one when it is not present. My understanding is that all methods of measuring blood sugar have some margin of error, so no meter will be perfect.
posted by primethyme at 11:06 AM on March 4, 2021

There aren't many many choices when it comes to CGM. There are two more choices aside from Dexcom and Freestyle:

Senseonics Eversense with an implanted sensor that lasts up to 90 days, and goes in the upper arm, not waist level.

Medtronics Guardian Connect, goes at waist level like everyone else.

I haven't seen any like true compare and contrast of all four systems on accuracy though.
posted by kschang at 11:50 AM on March 4, 2021

I have diabetes. I've used several different continuous monitors over the years.

The most instant, reliable way to check BG is to do the finger stick. That will give you the closest to
"What your BG is right this very second" that you can get.

The continuous monitors that link to your iPhone (or whatever) tend to be stuck into your fatty tissue on your mid-section or upper arm. Myself, I have modest love-handles and they are perfect placement for that. They will tend to give you a reading that is more reflective of what your BG was "a little while ago". Usually, that "little inaccuracy in time" isn't a big deal on a day-to-day basis - but on those times when your BG is dropping like a stone you will feel hypoglycemic before it registers on your meter. Learning to recognize the feeling of hypoglycemia is very important for these cases.

My doc always told me, "If you feel low and your continuous meter doesn't say so, trust your instincts and do a finger stick." I usually caught my lows before my meter did. Though the meter HAS woken me up in the middle of the night when I had a low. That's the big value of the meter for me: it can catch things when you are otherwise unable to do so.
posted by nathanfhtagn at 12:01 PM on March 4, 2021

The Libre 2 (second version) is about to come onto the market (End of March/Maybe April) in Canada and USA. It will have some simple alarms on it, and it significantly cheaper than a Dexcom. The Libre is reasonably accurate but the 2 is allegedly better. Might be worth a look.
posted by Northbysomewhatcrazy at 12:41 PM on March 4, 2021 [1 favorite]

The CGMs are not measuring blood glucose directly. They measure glucose in your interstitial fluid that varies with blood glucose levels. In my wife's case (type I diabetes with a Medtronic CGM) there is about a 15-20 minute lag with her actual blood sugar levels. Most of the time it's not a big deal, but if your glucose levels are falling or rising rapidly that lag can represent a significant difference and cause you to take the wrong actions. For example, the CGM is reading low but if your blood sugar is rising rapidly at that time your actual blood sugar may be fine. However, if you eat something to raise your blood sugar when it's not actually low and in fact increasing, you are only making the problem worse.

Also the Medtronic CGM accuracy is worse when she first puts it in and also on day 7, which is the day she changes it out.
posted by COD at 2:39 PM on March 4, 2021 [1 favorite]

My endocrinologist says glucose monitors, and in particular continuous glucose monitors, aren't very accurate for hypoglycemia. She also says that her awareness of the performance of these products is from about eight years ago.

This may be a red flag, or at least something alarming to consider. Perhaps I am mistaken.
posted by metabaroque at 6:59 PM on March 4, 2021

Best answer: Short version: the study you want is here. Six meters passed these authors' particular criteria (check the "Passes out of 3 Studies" column). Some of them have fairly inexpensive strips; some do not.

Having said that:

I'm type 1 diabetic and fingerstick and CGM user, so I have a fair amount of experience comparing finger-stick readings and CGM readings. As in: I'm a big enough data geek that I've done things like endurance bike rides and pausing every half hour to take a finger stick to chart it against the CGM data on my return.

My Dexcom G6 (and previous G5, though it wasn't quite as good) is really, like amazingly, good at reporting accurate blood glucose about 15 minutes behind, as COD mentions above, a fingerstick reading. (It's so much better than the Medtronic that I would rob a bank to pay out of pocket not to have to give it up.) It's not super-accurate for the first few hours after insertion but holds good accuracy out to day 10 when I remove it. I calibrate it once a day, two or three times a day on day 1, and it holds within about 10 points mg/dL difference when compared to my two fingerstick systems. Given the notorious large error bars allowed in home fingerstick systems (see the 2012 study that kicked off that mess), that's as good as I figure I can hope for.

Re hypoglycemia, seeing the blood sugar *trend* and having a CGM's alert system are huge, huge benefits. Like, it's hard to overstate just how amazing it is to be able to pull a screen out of my pocket (receiver or phone), take a two-second glance at it, and see a chart that tells me "oh, you're not low right now but if you keep up this trend, you're going to need to eat within the next 40 minutes." And the fact that it will beep at me if it's dropping too fast (but still in range) or if it drops too low is amazing. I try not to rely on it because then it would be a potential single point of failure, but I have definitely had it beep at me and make me realize I'd miscalculated and should take in some sugar.

- as mentioned above, when in doubt, go take a fingerstick measurement
- I've settled on a ReliOn Prime (Arkray, sold as WalMart) and a Freestyle Lite (Abbott); the ReliOn strips are much cheaper for me; it has slightly worse accuracy when comparing across lots; the Freestyle seems to be really solid but I only use it as my backup and verification so honestly haven't put the zillions of hours on it that I have on the ReliOn
- my previous main meter was a OneTouch Verio and it had the same performance as the ReliOn Prime but for WAY higher cost; not worth it

Thanks for putting up with my ramble! I'm around for messages if I can help answer any questions.
posted by introp at 8:19 PM on March 4, 2021 [4 favorites]

Dexcom is AFAIK the gold standard for CGM systems, but I've been quite happy with Medtronic. Talking to other people in my type 1 diabetic pump support group leads me to believe most people are more happy with Dexcom than Medtronic though.

In either case with Dexcom or Medtronic, you can set alarms/alerts when your sugars are dropping rapidly, and also when your sugars are approaching a low threshold. I'm not sure how long it takes for you to go from normal sugar ranges to hypoglycemia, but for me it's far more valuable to have a reading every five minutes that gives me a chance of a predictive alert than it is to fingerstick when I feel off. As you experience more hypoglycemic events your sense that you are going into hypoglycemia will diminish over the years. Continuous monitoring seems like the best choice as long as your insurance will cover the rather expensive sensors.

Since going to CGM I've experienced much, much less hypoglycemia than I used to with fingersticks.
posted by BrotherCaine at 4:58 PM on March 6, 2021

Beta Bionics and I think tandem are both working on technology for glucagon pumps in the US, and I know there are other options in development Internationally. You may want to keep an eye on that as most of those systems will require a specific CGM (probably Dexcom).
posted by BrotherCaine at 5:04 PM on March 6, 2021

Response by poster: To all who contributed to this thread, I want to say I've learned a ton and also feel informed for when I next talk to the doc (and metabaroque, I agree abt the red flag). I really appreciate it!
posted by 10ch at 11:02 AM on March 7, 2021

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