The Dexcom G6 is the best CGM on the market, but its sensor filtering (Kalman or particle?) has smoothness and/or continuity priors that cause persistent inaccuracies.
I observe these persistent inaccurate states on the fifth or sixth day using a sensor. Calibration doesn't help. The reading goes wrong and stays wrong.
It probably happens to you, too, but anyone who doesn't test with a glucometer will likely not notice the failure. You will be harmed by these inaccuracies. Persistent inaccuracy is different than the Gaussian (normal) error of a glucometer, which is far more benign.
Also, CGMs are slow. The reading is based on interstitial fluid and lags direct blood glucose test by 15 minutes or more.
I have completely abandoned the Dexcom G6 and have gone back to 16x daily finger stick blood testing. I am also on a low-carb/high-fat diet, which makes it easy to maintain normal human blood glucose. My HbA1c has been 4.9 for a decade.
I was overjoyed to use the CGM at first, but it turned out to be a net loss. If you want to control your diabetes, use a glucometer and adhere to a strict low-carb/high-fat (ketogenic) diet.
I've done accuracy studies of the G6 for a submission to the FDA, and while it's true they do filter out spikes, they're never more than 5mg/dL off from the measured value (which itself is usually within 10% of the real value). Interstitial lags are closer to 5 minutes when you're not experiencing severe perfusion issues, which is more than close enough for making dosing decision, especially considering subcutaneous insulin has similar or longer lag times (depending on lots of things of course, and subject to an individual's own body).
Any diabetic can confirm for themselves my claim about the Dexcom G6's unacceptable persistent error states.
Simply compare the CGM with your glucometer (testing 8x per day, for example), and watch the CGM go wrong (and stay wrong) on day 5 or 6 of using the sensor.
I wish what you said was true. I would love to have a CGM that works better than a glucometer, but they don't exist yet. In particular, the Dexcom G6 is inaccurate in a harmful way.
I’m T1 and I use the G6. I used to regularly check against a glucometer multiple times a day (without calibrating) to check accuracy, and found no issues. A blanket statement such as “the Dexcom G6 is inaccurate in a harmful way” is certainly not true in general, even if true for you.
Is there a good source for info on ketogenic diets for type 1 diabetics? My youngest has been on pump therapy for the past 5 years and is completely burnt out from all of the alerts and scares (some of it is self inflicted). She was on a medtronic closed loop system for 4 years and that was the source of most of her frustration. She's on g6+tslim now which has been much better, but she still falls off the wagon regularly.
I just think a keto diet would make it easier for her, but I'm seeing all sorts of conflicting info on it and her doctors don't support it. I've done it a few times in the past and getting started is the hardest part. I'd like for her to try but I'm getting no support on the idea. ?
Anecdotal, but a Keto diet has completely flatlined my BG — in a very good way. I’m talking about being in the range of 4.8 to 5.8 for weeks on end. My endocrinologist thinks I’m a wizard and has never seen anyone with 100% in range.
I also love that I never have to bolus with food. It’s the closest I can get to pretending I’m not a T1D. I just eat. If I’m full, I stop and don’t have to worry that I accidentally took too much insulin. To reiterate, I take zero boluses when I’m on the keto diet.
Doctors are against it because they’re dealing with ketoacidosis on a regular basis. Ketosis also means your body is producing ketones (which I believe is the source of confusion for doctors), but that’s fine because your BG is in a normal range. Technically you’re at higher risk for ketoacidosis when on the keto diet because of those ketones, but realistically your BG is not going to reach >15mmol/L so you don’t have to worry too much.
By the way, you may be interested in Loop[0] if you wanted to look at a more advanced closed loop system. It can handle both auto basal and auto bolusing.
> To reiterate, I take zero boluses when I’m on the keto diet.
I'm very surprised by this and would love to hear what you eat while doing keto. I'm T1 but still have to bolus when doing keto, even when doing zero carb and fasting for 18+ hours a day. I only need between 1 and 3 units but there's rarely an occasion when I don't need to bolus at all.
> Doctors are against it because they’re dealing with ketoacidosis on a regular basis.
The issue my endo has is that my BG is much lower than he would like. I've heard the phrase "too well controlled" so many times and it irritates me no end. His concern is that I'll lose awareness of low BG, and can't comprehend how I'm able to function as usual even when my BG is ~2.5 mmol/l (to clarify - I don't aim to run that low; my target range is 4-6).
Could you please share a bit more information about the insulin (kind, amount) you use during the keto diet? and how did you discover the right amount of insulin?
It seems to me, if one would let the insulin slip too low, one would be in danger of ketoacidosis, isn't that so?
I'm on a keto diet for chronic insulin resistance and obesity, caused by 50 years of high carb eating. (Every meal a sandwich, or including potatoes or rice, and lots of sugar.)
I got a CGM a few months ago to help me directly see the impact of the foods I'm eating. It has allowed me to fine tune my diet and get rid of everything that causes a noticable rise in my glucose. My daily graph now shows little more than than the natural daily cycle of glucose produced by my liver: starts rising before dawn, peaks around 10am, drops to my average by 6pm, and drops to daily low around 3am.
If I were a type 2 diabetic (I was headed there), I wouldn't need supplemental insulin because I'm not eating anything that increases my glucose. The only glucose in my blood is the small amount my liver puts there because I need it.
If I were type 1, I'd need to take insulin because my body wouldn't be making any at all. With my natural, consistent, and small-range daily pattern, it would be easy to predict my needs and take the right amount at the right time.
Everybody's body responds differently, so you have to experiment to see what works for you. The CGM has been a great tool for that. I also use a Keto-Mojo for blood glucose and ketone testing now and then.
What's worked for me is a diet of eggs, cheese, bacon, chicken, ground beef, ground pork, roast beef, turkey, pepperoni, kale, cabbage, Brussels sprouts, coffee, seltzer, bone broth, half & half, heavy cream, rebel ice cream (but not other keto ice cream brands), almond flour, ground pork rinds (as a bread crumb substitute), and probably some more I'm forgetting.
Typical advice is to stay under 20g net carbs, but I've found that I do better if I count total carbs instead for any non-veggie foods. Keto-friendly substitutes for flour and sugar mess me up most of the time, but I've found a few things that are ok. I also do intermittent fasting, only eating one or two meals during a 6-8 hour window, but I do much better if I fast for 36-48 hours. Dr Eckberg has some good videos on why fasting that long makes a difference.
Wow - thought I'd never find anyone else with my diet on HN, but (other than half & half, ice cream and Brussels sprouts), we're surprisingly close. I'd also add a few things, such as almond milk, homemade mayo, flax, cocoa powder, 100% cocoa squares, and head lettuce for burger wraps, but that's about it. Like you, I tried things like carbalose flour and erythritol with bad results, but stevia powder seems ok. I'm glucose intolerant but thin and would likely need some sort of drug if I wasn't eating this way - which I have been since 2008.
I did something similar for a while. Loved it. Great results.
How's your cholesterol, risk for heart disease, etc?
Having high LDL, I switched to a high fiber diet. My LDL hasn't budge.
So now I'm pondering what's next.
I have almost zero knowledge, opinions, ideas about what's best, for me or anyone else. The stuff I've read about cholesterol just confuses me.
One of the few things I did learn (about myself) is that calorie restriction works great. After a few days I barely notice. But adherence is very difficult when I'm in pain.
T1 here. I use OpenAPS with a G6 for closed looping (it's substantially better than Medtronic's looping algorithm), combined with a keto diet. The keto diet makes things a lot easier; there's no carb entry to do, so no opportunities for mistakes. I would indeed recommend it. Just make sure to count calories (at least initially) and keep them high enough; most people on keto diets are using them for weight loss, and that style of keto diet isn't sustainable.
Well, once you've finished "eating" your body fat, you can't sustain the calorie restriction. But at that point there's no reason too. For those of us prone to insulin resistance, we have to continue to eat low-carb to avoid putting the weight back on. (Very similar to how an alcoholic who's gotten sober has to continue to avoid alcohol.) But we don't need to have a caloric deficit anymore.
Your fat sources should be nuts and olive oil and chia seed, with some cheese and egg.
Healthy food with lots of healthy fat.
The brain uses ketones as fuel, so you will find that hypoglycemia is easily handled. In ketosis, your brain will have plenty of fuel, even if your blood glucose drops too low.
I can't say enough good things about my G6. It literally changed my life as far as how I interact with my diabetes.
- I feel safer when I go to bed, because it's there to wake me up if my blood gets low (or too high).
- I feel safer in general because I don't need to worry that my blood is low but I haven't noticed it; and that I'm going to just fall down face first while walking across the room.
- Testing my blood is just a matter of looking, vs going over to (or downstairs to) where the tester is.
- (Because of the above) I have a better "feel" for how my blood sugar reacts to various foods and activities.
- When I'm having trouble with my sugars (morning highs, for example), I can see what my history has been via nice graphs on their web site.
Honestly, it's amazing. While I respect your choices, I can only assume you weren't taking full advantage of just how wonderful having the G6 is.
My numbers tend to range in the high 5s to low 6s. That being said, the past two years have been rough because of a thyroid issue, plus 2 different drugs that impact blood sugar a lot (my blood sugar was hovering around 180 all day today, having not eaten since last night, and taking 80 units of short acting insulin over 4 shots... its been pretty crazy)
I think the usual recommendation is before meals, two hours after meals and before going to bed. So that was 7 times a day for me. The big problem with testing more times is that you are literally damaging your fingers and hoping that they heal before you need to use that area on your finger again. For me this didn't always happen and is one of the reasons I love my FreeStyle Libre.
I observe these persistent inaccurate states on the fifth or sixth day using a sensor. Calibration doesn't help. The reading goes wrong and stays wrong.
It probably happens to you, too, but anyone who doesn't test with a glucometer will likely not notice the failure. You will be harmed by these inaccuracies. Persistent inaccuracy is different than the Gaussian (normal) error of a glucometer, which is far more benign.
Also, CGMs are slow. The reading is based on interstitial fluid and lags direct blood glucose test by 15 minutes or more.
I have completely abandoned the Dexcom G6 and have gone back to 16x daily finger stick blood testing. I am also on a low-carb/high-fat diet, which makes it easy to maintain normal human blood glucose. My HbA1c has been 4.9 for a decade.
I was overjoyed to use the CGM at first, but it turned out to be a net loss. If you want to control your diabetes, use a glucometer and adhere to a strict low-carb/high-fat (ketogenic) diet.