For me the best insight learned from wearing a GCM is that a cardio exercise with 150bpm heart rate for 40min+ is probably not healthy. I would easily see my glucose level drop to below 80 mg/dL (5 mmol/L) 30min into the exercise. I always thought the exhaustion towards the end of my exercise was due to normal fatigue, and never thought it was caused by hypoglycemia.
Now I would exercise and closely monitor my glucose level, then adjust my intensity when it dip lower than 100 mg/dL (5.5 mmol/L). It made the cardio exercise much more bearable, and easier to stick to it as a daily routine.
guiambros · 2h ago
I've been using a CGM on and off for the last year, and it has given me a whole new perspective about food and nutrition.
I discovered that a bunch of things I thought were reasonably healthy actually caused huge glycemic spikes -- e.g., white bread in the morning, croissants, dried mangos, excessive amount of fruits, etc.
I also discovered the importance of what you eat for your first meal in the day (either breakfast or lunch), or how to better order what you eat (fibers, fat and protein first, carbs last), light movement after eating reduces 20+ mg/dl, and more.
At this point I don't even need to wear a CGM every day; I can tell my glucose level just by thinking of what I ate earlier.
I still wear one when I'm traveling for work, as I know I'll have less control over food and calorie intake (airplane meals, restaurants, team lunches, etc).
ps: if you're interested in learning more even without using a CGM, strongly recommend "Glucose Revolution" [1].
> I discovered that a bunch of things I thought were reasonably healthy actually caused huge glycemic spikes -- e.g., white bread in the morning, croissants, dried mangos, excessive amount of fruits, etc.
I wonder if this amounts to optimization of an easy-to-measure and reasonably-looking but incorrect metric, much like the previous "common sense" wave of "fat makes you fat" that led several generations into a dead end.
You assume above that glycemic spikes are unhealthy which I think was never proven for the general population. Eating too much sugar or eating too much in general is bad, but I'm not aware of evidence that croissants kill you if you eat reasonably.
Another thing to note: one of the potential suspects in the obesity epidemic is HFCS, and fructose doesn't actually cause glycemic spikes. If this turns out to be true, then parallels with the "fat makes you fat" theory become uncannily strong.
I tend to think this could be the case because it matches my personal observations. I moved to France a few years ago and the amount of croissants I and people around me consume is at the stereotypes level. My weight is stable but each time I go to US for a couple of weeks I bring back 3-5 extra kilos. Something is seriously different between the food here and there, and I don't think it's glycemic spikes per se.
Etheryte · 25m ago
Large glycemic spikes are are an issue, but the problem is not obesity. Obesity is concerned with calories in and calories out and our current obesity epidemic is largely attributed to the fact that we eat more calories and move less. Most other discussion points are secondary to that fact. Glycemic spikes on the other hand are linked to increased insulin resistance, heightened risk of diabetes, cardiovascular disease and so on. The two are linked, but not the same problem.
andrewflnr · 49m ago
I only casually follow these things, but my understanding is that interest in glycemic spikes is not really about obesity or fat at all, but more about diabetes-related issues, insulin resistance I think.
bboygravity · 54m ago
The difference is corn syrup (in everything) vs sugar from sugar beets. Corn syrup has way more calories por unit sweetness.
Llamamoe · 40m ago
> I discovered that a bunch of things I thought were reasonably healthy actually caused huge glycemic spikes -- e.g., white bread in the morning, croissants, dried mangos, excessive amount of fruits, etc.
It's baffling that those things are considered healthy in the first place - white bread, pasta, rice, potatoes contain so much starch(which is rapidly broken down into glucose) that their glycemic index is higher than that of table sugar.
Likewise, the entire reason why fruit are tasty is because they're sugar bombs. The absorption is slightly slowed by cell wall digestion, and they have antioxidants, vitamins, etc. But still. It's sugar.
> I also discovered the importance of what you eat for your first meal in the day (either breakfast or lunch), or how to better order what you eat (fibers, fat and protein first, carbs last), light movement after eating reduces 20+ mg/dl, and more.
Having read science on the topic, you're extremely right on botr counts - limiting carbs in the first meal of the day moderates glucose spikes for the entire rest of the day, and moving after high carb meals is critical because muscles uptake glucose independent of insulin signaling, massively reducing the stress on your metabolism.
DoingIsLearning · 54m ago
> At this point I don't even need to wear a CGM every day; I can tell my glucose level just by thinking of what I ate earlier.
Would be interesting to create some form of model of that and see how accurately you could 'guess' gliglycemia levels for a specific individual just by knowing biometric info and accurate food intake.
As in could you potentially appify your newly acquired intuition?
WatchDog · 1h ago
I've been using "freestyle libre" devices on my diabetic cat, but they are quite expensive(~$110 AUD), and typically don't last the whole 14 day period before failing. Although I imagine they are much more reliable on a human.
I've stopped using them because it's just a bit too expensive, and my cat's diabetes is more stable now.
I opened up a freestyle libre 2, it has a EM9304 bluetooth SOC, and a TI RF430 NFC microcontroller, chatgpt deepresearch estimated the bill of materials to be about $5 USD[0].
Some companies[1] are developing reusable CGMs, the electronics are reusable, but the glucose oxidase probe, and applicator needle are still consumable. I'm not sure if that will bring the costs down much, it doesn't seem like the BOM is the main factor in the price of existing CGMs anyway.
> it doesn't seem like the BOM is the main factor in the price of existing CGMs anyway
No. A huge reason for the cost is (1) costs in R&D but also (2) the customer service/replacement requirements/etc required for medical devices.
If you were diabetic, and had a prescription for these devices, you'd be able to call Abott/Dexcom and get a replacement to a failed device shipped to you overnight. If the device didn't last the fully spec'd lifespan, you'd be eligible for replacements... etc
mlsu · 5m ago
And on R&D; the QC bar for software and manufacturing is much higher. Every process has validation testing. So it is expensive both in R&D and manufacturing.
Another thing is that these off the shelf CGMs don't really differ in quality to their prescription only counterparts, which have a pretty extreme risk profile (patient death or hospitalization if it spits out the wrong number). They use the same parts so those costs are inherited.
bix6 · 2h ago
I believe these cheaper devices are not very accurate ie accuracy range of 20% which is a fairly wide window. I’ve also heard there are many things that can impact your glucose even with the same meal like time of day, exercise, stress, sleep, etc. So if you actually want to find the patterns you’d need the expensive CGM over many months.
friendzis · 1h ago
Does not really matter.
You are interested in the trend, not absolute numbers, anyway, which, aside from having some "propagation delay", tracks blood glucose pretty well.
loremm · 2h ago
Is that true? I have no perspective but it's relied on by diabetics and if since they can't regulate it themselves, if the readings are off and they gave themselves insulin, they would know it is wrong. Maybe the OTC ones is different than the diabetic one but I didn't think so
nmehner · 1h ago
As a diabetic having alarms is the most important thing. Measurements are not that accurate (neither is the finger prick method: If sometimes get a difference of 20% comparing two measurements from both hands). But also the "ok" range of 3.8 mmol/L to 10 mmol/L is quite large and levels can rise/drop 20% in minutes. So it is still quite helpful.
With the CGM there is also an additional delay of about 15 minutes in the measurements. Mostly you want to be triggered when something strange happens and then you do a manual measurement to confirm.
A false alarm of low blood sugar is annoying, but it is a lot better than collapsing. You can relax a lot more if you know you will get an alarm.
djur · 2h ago
Stelo is basically just a consumer packaged version of the Dexcom G6, and in both cases they warn you to use a finger stick to verify unexpected readings. But finger sticks can be really inaccurate, too. For many diabetics it's not a life-or-death matter (only 1 in 4 type 2 patients end up using insulin), and the important thing is the trend over time.
I've personally found my CGM to be really useful in understanding the effect of diet, sleep, stress, etc. on my blood glucose, like the OP says, but you definitely get some weird readings sometimes. Yesterday a new unit told me that my blood glucose dropped below 70 for 2 hours. It definitely didn't! After a while it got itself straightened out in time to scold me for eating some corn chips.
bix6 · 1h ago
Most T1Ds I know use a CGM now as they are much more accurate than they used to be. But they are expensive so insurance generally covers for T1D but not T2D. You can always double check with a finger stick though as that uses blood instead of interstitial fluid. My friend uses a Tslim which uses a CGM to adjust her insulin automatically.
privatelypublic · 2h ago
They're not any different. CGM's have issues- sometimes need to be calibrated against a finger stick (officially, they always need to be)
In the end though- it's still a bit of fungal extract painted onto an electrode, and an ADC that reads the value every so often. Like any other glucose monitor.
No comments yet
utopcell · 2h ago
> accuracy range of 20% which is a fairly wide window
what backs this factoid?
bix6 · 1h ago
I’m having a hard time finding a proper comparison table but the top end CGM systems now seem to be around 8% MARD. This study is for BGMS but it shows a range of 2% to 20%: https://pmc.ncbi.nlm.nih.gov/articles/PMC9445334/
It's open source and supports all CGM sensors that I know of.
It has the ability to "broadcast" your data to various destinations and has a built-in https server to export a quick summary view to share with your doctor. It also supports exporting to Abbot LibreView so your significant others can use the LibreView app to view your data.
Don't be intimidated by the UI: it's weird and seemingly outdated, but EVERY part of the UI has a dedicated "help" button that you can click and read for details.
Couldn't be happier since I ditched the Freestyle Libre app (it failed to open after an Android update).
imjonse · 50m ago
The author does not seem to go into details, so I am curious what actually surprising conclusions can be drawn from wearing one of these devices?
Croissants and muffins being unhealthy should be no surprise. I am more interested in findings like food that gets a bad rap being not that unhealthy and supposedly healthy food being bad.
Llamamoe · 36m ago
Pizza is much more nutritionally complete than you'd think, especially if it has meat(or beans, for some reason), the only real problem is people eat SO MUCH at a time.
People also refuse to understand that juice is basically sugar water with some extra flavor, vitamins, and antioxidants that don't change how unhealthy it is for you.
White rice is basically pure carbs with barely any nutrients.
Fastfood is heavily processed but often contains enough vegetables, meat, etc to not be that bad all things told.
jaggs · 24m ago
One of the more interesting findings is the impact of combining different food intakes at the same time. It can have a significant effect in lowering spikes.
ViscountPenguin · 1h ago
Is there any actual data on the long term use of these devices in non-diabetics?
This feels like geek bait, imo. A nice simple metric to obsess over, and to optimise. With a super simple (therefore presumably wrong) biological model to back up it's worth.
It seems to be, that nothing particularly good has come of prior trends in quantified self-health (for regular consumers, pun intended, at least); and this seems to come packaged with a very real risk of orthorexia.
tptacek · 1h ago
In a couple of cases, meals that I thought would be fairly healthy (or at least not terrible) were pretty terrible. There'll be some things that I'll avoid eating more than I had before.
Someone chime in with what they think these might be! Should I be eating less broccoli?
yegle · 1h ago
King's Hawaiian Roll.
It doesn't taste like it contains a lot of sugars, at least not as sweet as other desserts like a cake. But two rolls (weight wise, very small amount) would send my glucose to sky high.
leakycap · 3h ago
The author's mention of the Hawthorn Effect fascinated me; I hadn't considered that with devices your care team can monitor.
It will change a lot of lives when some device that doesn't draw blood can continuously monitor glucose, like a smartwatch.
shreezus · 1h ago
I believe we will see integrated optical glucose sensors in a popular consumer wearable fairly soon.
I don't think they'll be as accurate as blood sensors, however they will be a game-changer for many people (pre-diabetics, or gestational diabetes etc).
privatelypublic · 2h ago
Pretty sure optical glucose is already a thing- it's just not very accurate yet.
leakycap · 29m ago
I have used my phone camera to determine blood pressure, but I have yet to see a common consumer device with optical glucose monitoring.
I'm suggesting that it will change the world when it is an integrated part of something many/most of us buy and would eventually upgrade to.
Great resources. It seems we'll see BP monitoring integrated in a mainstream base smartwatch before we'll get optical glucose monitoring.
utopcell · 2h ago
I share the author's enthusiasm about GCM devices. I am also finding that I need to change the over-patch long before the 15-day window because it gets messed up. I've found these [1] quite useful.
What CGM device would you recommend for a first try?
thor-rodrigues · 45m ago
What I find absolutely infuriating is that Abott (Freestyle Libre 1-3 devices) region locks their monitoring app depending on your region.
My father is T1 is uses the Libre CGM system for a couple years now. Libre users in the US and Europe can enjoy direct integration with their iOS devices, including constant updates and most importantly, notification alerts for dangerously high or low glucose levels, and it is even possible to share live updates of this with close family members or caretakers.
But none of this is available for my dad, as he lives in Brazil. Even though the product is same, he cannot download the iOS apps over the AppStore, as they are region locked.
As a healthy, non-diabetic adult I wore a Continuous Glucose Monitor (CGM) to measure my blood sugar for two weeks
The sensor was convenient to use and painless to apply, and was barely noticeable during the two weeks it was on my arm.
In analyzing my blood sugar levels, I learned a lot about my body’s response to different foods and exercise; I could identify some foods that spike my glucose.
Two weeks is too short to make detailed improvements to my nutrition in order to stabilise glucose levels — further monitor and experimentation will be needed.
ars · 1h ago
I wore one, but had some trouble with the glue, by day 8 or so it seemed like it was on the verge of falling off, so I added some medical tape which annoyed my skin.
I suspect these devices will never go beyond 14 days at a time simply because of the glue issue. My skin was also pretty irritated once I removed the device, with some blood where the device sat.
If you chose to wear one, especially in the summer, work very hard at removing all oils from your skin before you apply it. Soap and water (preferably real soap, not SLS), and then alcohol to get everything.
I discovered that my wake/sleep cycle affected my blood sugar as much as, or even more than, what I ate.
stkhlm · 32s ago
Some people do have a lot of issues with the adhesive and skin reactions. I am lucky and don't have that.
I use an Anubis, a modified Dexcom G6, (https://www.loopandlearn.org/anubis/), which allows up to 60 days of wear. Although realistically I've never gone over 25 days. This is with adding over patches as the adhesive starts to fail though. The one I'm wearing right now is on day 18 and still doing great.
After day 10-12 I also start to do daily checks with a blood glucose meter to verify that the readings from the CGM are still correct.
duskwuff · 52m ago
> I suspect these devices will never go beyond 14 days at a time simply because of the glue issue.
The sensor chemically wears out over time too - the time limit is based on how long the manufacturer can guarantee good readings for.
hyperbolablabla · 1h ago
> "i would be amiss"
Huh, never seen that typo before. Should be "remiss"
Now I would exercise and closely monitor my glucose level, then adjust my intensity when it dip lower than 100 mg/dL (5.5 mmol/L). It made the cardio exercise much more bearable, and easier to stick to it as a daily routine.
I discovered that a bunch of things I thought were reasonably healthy actually caused huge glycemic spikes -- e.g., white bread in the morning, croissants, dried mangos, excessive amount of fruits, etc.
I also discovered the importance of what you eat for your first meal in the day (either breakfast or lunch), or how to better order what you eat (fibers, fat and protein first, carbs last), light movement after eating reduces 20+ mg/dl, and more.
At this point I don't even need to wear a CGM every day; I can tell my glucose level just by thinking of what I ate earlier.
I still wear one when I'm traveling for work, as I know I'll have less control over food and calorie intake (airplane meals, restaurants, team lunches, etc).
ps: if you're interested in learning more even without using a CGM, strongly recommend "Glucose Revolution" [1].
[1] Glucose Revolution: The Life-Changing Power of Balancing Your Blood Sugar - https://www.amazon.com/Glucose-Revolution-Life-Changing-Powe...
I wonder if this amounts to optimization of an easy-to-measure and reasonably-looking but incorrect metric, much like the previous "common sense" wave of "fat makes you fat" that led several generations into a dead end.
You assume above that glycemic spikes are unhealthy which I think was never proven for the general population. Eating too much sugar or eating too much in general is bad, but I'm not aware of evidence that croissants kill you if you eat reasonably.
Another thing to note: one of the potential suspects in the obesity epidemic is HFCS, and fructose doesn't actually cause glycemic spikes. If this turns out to be true, then parallels with the "fat makes you fat" theory become uncannily strong.
I tend to think this could be the case because it matches my personal observations. I moved to France a few years ago and the amount of croissants I and people around me consume is at the stereotypes level. My weight is stable but each time I go to US for a couple of weeks I bring back 3-5 extra kilos. Something is seriously different between the food here and there, and I don't think it's glycemic spikes per se.
It's baffling that those things are considered healthy in the first place - white bread, pasta, rice, potatoes contain so much starch(which is rapidly broken down into glucose) that their glycemic index is higher than that of table sugar.
Likewise, the entire reason why fruit are tasty is because they're sugar bombs. The absorption is slightly slowed by cell wall digestion, and they have antioxidants, vitamins, etc. But still. It's sugar.
> I also discovered the importance of what you eat for your first meal in the day (either breakfast or lunch), or how to better order what you eat (fibers, fat and protein first, carbs last), light movement after eating reduces 20+ mg/dl, and more.
Having read science on the topic, you're extremely right on botr counts - limiting carbs in the first meal of the day moderates glucose spikes for the entire rest of the day, and moving after high carb meals is critical because muscles uptake glucose independent of insulin signaling, massively reducing the stress on your metabolism.
Would be interesting to create some form of model of that and see how accurately you could 'guess' gliglycemia levels for a specific individual just by knowing biometric info and accurate food intake.
As in could you potentially appify your newly acquired intuition?
I've stopped using them because it's just a bit too expensive, and my cat's diabetes is more stable now.
I opened up a freestyle libre 2, it has a EM9304 bluetooth SOC, and a TI RF430 NFC microcontroller, chatgpt deepresearch estimated the bill of materials to be about $5 USD[0].
Some companies[1] are developing reusable CGMs, the electronics are reusable, but the glucose oxidase probe, and applicator needle are still consumable. I'm not sure if that will bring the costs down much, it doesn't seem like the BOM is the main factor in the price of existing CGMs anyway.
[0]: https://chatgpt.com/share/686225c7-11ac-8005-aa4a-f420415e21...
[1]: https://www.rightest.com/global/rightestifree2cgm/
No. A huge reason for the cost is (1) costs in R&D but also (2) the customer service/replacement requirements/etc required for medical devices.
If you were diabetic, and had a prescription for these devices, you'd be able to call Abott/Dexcom and get a replacement to a failed device shipped to you overnight. If the device didn't last the fully spec'd lifespan, you'd be eligible for replacements... etc
Another thing is that these off the shelf CGMs don't really differ in quality to their prescription only counterparts, which have a pretty extreme risk profile (patient death or hospitalization if it spits out the wrong number). They use the same parts so those costs are inherited.
With the CGM there is also an additional delay of about 15 minutes in the measurements. Mostly you want to be triggered when something strange happens and then you do a manual measurement to confirm.
A false alarm of low blood sugar is annoying, but it is a lot better than collapsing. You can relax a lot more if you know you will get an alarm.
I've personally found my CGM to be really useful in understanding the effect of diet, sleep, stress, etc. on my blood glucose, like the OP says, but you definitely get some weird readings sometimes. Yesterday a new unit told me that my blood glucose dropped below 70 for 2 hours. It definitely didn't! After a while it got itself straightened out in time to scold me for eating some corn chips.
In the end though- it's still a bit of fungal extract painted onto an electrode, and an ADC that reads the value every so often. Like any other glucose monitor.
No comments yet
what backs this factoid?
It's open source and supports all CGM sensors that I know of.
It has the ability to "broadcast" your data to various destinations and has a built-in https server to export a quick summary view to share with your doctor. It also supports exporting to Abbot LibreView so your significant others can use the LibreView app to view your data.
Don't be intimidated by the UI: it's weird and seemingly outdated, but EVERY part of the UI has a dedicated "help" button that you can click and read for details.
Couldn't be happier since I ditched the Freestyle Libre app (it failed to open after an Android update).
Croissants and muffins being unhealthy should be no surprise. I am more interested in findings like food that gets a bad rap being not that unhealthy and supposedly healthy food being bad.
People also refuse to understand that juice is basically sugar water with some extra flavor, vitamins, and antioxidants that don't change how unhealthy it is for you.
White rice is basically pure carbs with barely any nutrients.
Fastfood is heavily processed but often contains enough vegetables, meat, etc to not be that bad all things told.
This feels like geek bait, imo. A nice simple metric to obsess over, and to optimise. With a super simple (therefore presumably wrong) biological model to back up it's worth.
It seems to be, that nothing particularly good has come of prior trends in quantified self-health (for regular consumers, pun intended, at least); and this seems to come packaged with a very real risk of orthorexia.
Someone chime in with what they think these might be! Should I be eating less broccoli?
It doesn't taste like it contains a lot of sugars, at least not as sweet as other desserts like a cake. But two rolls (weight wise, very small amount) would send my glucose to sky high.
It will change a lot of lives when some device that doesn't draw blood can continuously monitor glucose, like a smartwatch.
I don't think they'll be as accurate as blood sensors, however they will be a game-changer for many people (pre-diabetics, or gestational diabetes etc).
I'm suggesting that it will change the world when it is an integrated part of something many/most of us buy and would eventually upgrade to.
Existing smart watches that claim to do this are basically garbage. Just use a random number generator instead.
Apple and Samsung are supposedly working on it: https://www.forbes.com/sites/davidphelan/2025/01/26/samsung-... But it seems to be hard and from what I have seen the new Galaxy Watch 8 won't have this feature.
[1] https://www.amazon.com/dp/B0C4PKMJTN
My father is T1 is uses the Libre CGM system for a couple years now. Libre users in the US and Europe can enjoy direct integration with their iOS devices, including constant updates and most importantly, notification alerts for dangerously high or low glucose levels, and it is even possible to share live updates of this with close family members or caretakers.
But none of this is available for my dad, as he lives in Brazil. Even though the product is same, he cannot download the iOS apps over the AppStore, as they are region locked.
TL;DR:
As a healthy, non-diabetic adult I wore a Continuous Glucose Monitor (CGM) to measure my blood sugar for two weeks
The sensor was convenient to use and painless to apply, and was barely noticeable during the two weeks it was on my arm.
In analyzing my blood sugar levels, I learned a lot about my body’s response to different foods and exercise; I could identify some foods that spike my glucose.
Two weeks is too short to make detailed improvements to my nutrition in order to stabilise glucose levels — further monitor and experimentation will be needed.
I suspect these devices will never go beyond 14 days at a time simply because of the glue issue. My skin was also pretty irritated once I removed the device, with some blood where the device sat.
If you chose to wear one, especially in the summer, work very hard at removing all oils from your skin before you apply it. Soap and water (preferably real soap, not SLS), and then alcohol to get everything.
I discovered that my wake/sleep cycle affected my blood sugar as much as, or even more than, what I ate.
I use an Anubis, a modified Dexcom G6, (https://www.loopandlearn.org/anubis/), which allows up to 60 days of wear. Although realistically I've never gone over 25 days. This is with adding over patches as the adhesive starts to fail though. The one I'm wearing right now is on day 18 and still doing great.
After day 10-12 I also start to do daily checks with a blood glucose meter to verify that the readings from the CGM are still correct.
The sensor chemically wears out over time too - the time limit is based on how long the manufacturer can guarantee good readings for.
Huh, never seen that typo before. Should be "remiss"
I think it is fine. It would be remiss of me to say otherwise.