Damage occurs after 140 mg/dL...but that's not the whole story

We read repeated everywhere now that blood glucose above 140 mg/dL will cause nerve damage, and that at 100 mg/dL beta cells get stressed and they die at 110 mg/dL.

But when you look closely at the studies that demonstrate the above, you see that they are talking about the bg value at the 2 hour mark. This is very important to understand. The studies demonstrate that if your bg is as high as 110 mg/dL at the 2 hour mark, your beta cells die; more than 140 mg/dL at the 2 hour mark, nerve damage occurs; etc.

All of this is to be taken seriously. But now that we are armed with CGMs, we should ask for more accurate studies. Can we determine more precisely what bg we must stay under at all times to avoid all diabetes-created complications?

Update: For those of you asking for the research, here's a very good resource that summarizes and links to the research that I referenced in my post:


Great post! True, true, true.

Given that many are told 180 postprandial is fine & not to go to sleep not below 150, this could mean an reversal of targets. I’m all for that!

The medical profession will need to revise its belief system that a narrow range can be maintained without severe hypoglycemia.

I find this reassuring, because I find it depressing to read statements that say we are damaging our body every time our blood sugar goes over 140. Even on my best-best days it’s impossible for me not to go that high at least a few times. Sometimes I go to bed fine and wake up in the middle of the night to find I’m that high, or sometimes I’m fine in the middle of the night but high in the morning, or sometimes I spike that high after eating a meal that is usually fine, or sometimes after a low (even one I haven’t overtreated) I’m that high, or some days when dealing with illness or stress or female hormonal cycles I’m that high ALL DAY no matter what I do …

If I had a CGMS maybe I could avoid some of the highs, but without one I feel like I must be doomed to die of horrible complications at the age of 50 based on some of this stuff I read! After all, I’ve had diabetes for over 18 years already (at age 28) and I’m sure not a day has gone by when I haven’t gone over 140 at least once or twice.

For a two-hour goal, though, that’s much more manageable. At one time a few months ago I could manage that with a fair amount of confidence. Now my control is out of whack and I’m lucky if I’m under 200 after a meal, but I’m working on that.

No , you don’t have to die at age 50 , because of complications …I met a gent last year, 76 years of age , diagnosed at 2 years of age and going strong ( he received a National Award from the CDA ) … I don’t think he wears a pump , neither CGMS .
My A1C’s have been far from " perfect" , what ever that means …and NO complications , living with diabetes 27 plus years …I am glad I have fewer lows because of technology , including better insulins , than when I was prescribed NPH ( you know that one, no doubt ) . And you said, you are working on getting better results …my hat off to YOU Jennifer !

Well so far 18.5 years in I have no complications and I don’t plan on developing any anytime soon! But according to some of the stuff I read you must have PERFECT control to avoid those complications, otherwise it’s just luck. Which I just find depressing!

There is a book called the 50 Secrets of the Longest-Living People with Diabetes which is a great read, very inspirational, and none of the people in that book are perfect … they all have highs and lows like most of us. Some have complications but it’s still a great read!

What studies have you found on the subject? This is a complicated issue. Studies also suggest that there are factors (such as TXNIP deficiency, EGCG and Rutin, etc) that are protective and/or damaging to the beta cells in the face of hyperglycemia. I think there is also confusion about whether long-term average control at the 2-hr mark bears any relation to transient values. What I can tell you is that having controlled my HbA1 < 6.5% for the last 4 years has not been enough to avert diabetic neuropathy. So at least for me, 140 mg/dl at 2hrs is probably insufficienct. I do think everyone is different.

I also think you are right that there is limited evidence that beta cells “die” at 100 mg/dl. In fact, given that I have spent some years with consistent fasting blood sugars above 100 mg/dl, I would have to say that is not absolutely true.

I don’t think there’s any guaranteed number that’s out there. I don’t know about your generalization that “above 140 mg/dL will cause nerve damage”, I’ve been a T1 for most of half a century now and I went above 140mg/dL almost every day for the past 30 years. (I say “almost” because I’ve had some good days where I never went 140… and I’ve had some bad days where I never went below 140! Don’t forget that home bg monitoring was simply nonexistent for my first years.) I’m sure there’s some not-yet-detected cumulative damage in me, still below the threshold of the neurological tests they love to run me through, but the thought that a single number above 140 causes nerve damage… I just don’t believe it’s so simple that there’s some magic number below which you’re guaranteed no damage.

The DCCT was groundbreaking because for the first time it plotted complications like neuropathy, retinopathy, kidney disease vs A1c (a stand-in for average bg) and showed there was a clear relation. This was astonishingly clear. Maybe the newbies don’t know this but before the DCCT there were real medical doctors that didn’t believe in tight control.

BUT… Even in the DCCT, the most well-controlled, intensively treated patients, had a much higher rate of complications than non-diabetics.

So, I don’t think there’s a MAGIC NUMBER below which anyone is safe. I think that stable normal range bg’s and good control (without having many serious hypos) should always be a goal. If you want to make me feel bad because I ever broke 140, you can try, you won’t succeed. But should I tell everyone in the world that they should never break 100? I can’t. For one, I don’t see how it would be humanly possible - I struggle ENORMOUSLY to keep my after-meal peaks (not just one and two hours, but 3 and 4 and 5 hours too, those proteins getting converted to carbs are an incredibly pesky and unrelenting trend) below 140 not all the time, just some of the time!

And don’t forget the other end of complications… while I don’t have neuropathy, retinopathy, kidney disease, etc. after most of half a century, I have been in the ER a couple times with extreme hypos. Scary stuff whether I’m high or low.

Jennifer, I will have to get that book… I have heard great things about it. I am 42 years type one diabetic and do not have major complications, just a little tingling in my legs and back, which may or may not be from diabetes,; as spine and bone issues run in my family, so says my neurologist.
I have highs and lows at least every other day…but am trying to even things out… as I feel much better with more stable blood glucoses.

Do not fret about the numbers too much: I love my life and I am active and happy. No one has PERFECT CONTROL.We do the best we can . I try not to linger in highs or lows…It makes a great difference in day to day life.

God Bless,

Thank you, Nel. Words of wisdom.

That all nondiabetics would have the same damage, and that doesn’t make sense.

just lovely! excuse me while I bang my head into my desk. stoopid pancreas

Damage is not entirely caused by the ONE occasional or random reading above the marks above… But it can be caused when we are constantly above 140 mg/dL, for a very extended period of time… Sometimes, people use the excuse of that they haven’t gotten any complications to justify staying at higher numbers, or being happy at higher numbers. By the way, this is the same excuse noncomplicant diabetics use not to take care of themselves at all: “Why should I diet? Nothing’s bad happened to me yet…” This is NOT a good excuse to not try for tight control.

While we are ALL different – and we are all different in how prone we are to complications… Some more than others, and at different levels than others… We should all strive for getting as close to that tight control, as much as we can… For some that means 180 mg/dL… For others, it can be 160, or 150… But we need to at least try… We shouldn’t play Russian roulette with our health, all the time, to just throw it out to chance or luck, which is what it really is. (Not a blessing.)

My gut feeling is that the simple model of “no nerve damage” or “yes there is nerve damage” is way too abrupt and not useful. My gut feeling is that I (a T1 diabetic for most of half a century) have some cumulative damage to lots of parts of me but somehow it does not rise to detection by conventional diagnostic methods.

Other people have different feelings, that there is a magic number below which there is no damage, and above which there is detectable damage. They would probably make some excuse if they were to know that my bg was above 1000 when I was diagnosed in DKA but somehow I don’t have all the complications yet. At the same time a lot of T2’s are diagnosed well after a lot diabetic complications have set in.

There is a certain amount of medical evidence relating non-diabetics with higher-than-normal A1C’s to some cardio and microvascular risks, risks that diabetics (especially those with A1C’s but realistically all diabetics) have in spades. I think that applying this research to diabetics can have value but I think that the application is not straightforward. And certainly not as straightforward as a single magic number.

I am not advocating Russian roulette, Mis LIZ… Diabetes management is prudent and necessary I just hate to see people getting hung up and so depressed about a 141 blood sugar that may occur randomly. I know you do not share my views on spirituality, and I do not expect you to. I am not HAPPY with higher numbers… I just know that much of type one diabetes is accepting a number as a number and not a self-judgement. And I do feel blessed not to have complications… There are chance events that occur in life,: It is Part of the human condition . But I also believe that there is a divine plan for my life that does not include me getting sick from diabetes; and if God changes that plan, I will know about it and be able to deal with it with His help

We will have to agree to disagree on this one.

God Bless,

Love you, Brunetta.

Thanks Ms Robyn. Love you too. Kudos to Everyone who took the time to comment on this fascinating thread…

God Bless,

Like I said, “Damage is not entirely caused by the ONE occasional or random reading above the marks above…” I was not directly speaking to you advocating Russian roulettes (but there are those who do)… and I agree that we shouldn’t get hung up on the random 141’s… What I said, and which you seem to have ignored, is that we need to at least TRY… And not simply devote to chance, or God’s good graces, that we won’t get complications by always being really high… With our best tries, we are always going to have some off numbers, and that is OKAY… But we can’t use the ‘complications are random’ excuse to NOT try and not get closer to tighter control.

I was just driving to work this am thinking about this! I am the type who would like to have straight forward information to follow. I get that all bodies are different (and all diabetics are surely not the same,) but what IS the honest truth? So many doctors have different views (quite varied) and I find this super frustrating. Simply put: If one has diabetes, what are the straightforward general guidelines? Why are the numbers SO different? UGH.

Clearly anyone who comes to a site like this one is interested in diabetes and their health. So I doubt there is anyone here who is not putting in effort to maintain or better their control.

But for many type 1s it’s not just “one occasional reading” over 140, but multiple readings each day, and this doesn’t mean they are slacking off with their health or not trying. It’s really hard to avoid minor highs like that, and lots of us devote attention to avoiding the major highs … 200s, 300s, etc. I have been trying for an A1c below 6.5 for the past three years and every time I get close to that range (6.4, 6.6 … my two lowest A1c’s ever) I end up with too many lows (daily) and losing symptoms, which is not safe. So I have settled on an A1c of 6.7 or 6.8 or so because otherwise I will drive myself insane constantly striving for a goal and never achieving it.

It’s a LOT of work to keep my A1c below 7.0 (measuring food with a scale, adjusting pump settings almost daily, keeping logs, not to mention the basics having a good diet and exercise daily), and when you put in all that work constantly, it’s then kind of discouraging to be told that you’re still doing damage because some hours each day are spent above that target range, even though we try our best. I think that is where I and some others here are coming from.

You are doing the best you can Ms. Jen…As you said “Everyone here is putting in an effort to maintain or better their control”.
I had an a1c from a lab test at 7.0 in January, have had it as low as 5.7 about three years ago, but that was with a lot of lows… I feel the best at below seven so , and higher than 5.9, so that is what I am striving for
Keep up your hard work and don’t get discouraged!!!

God BLess,