" How Does Hyperglycemia Cause Damage And What Can We Do To Avoid It?" by Alan Shanley

We all know that hypoglycemia can cause immediate symptoms that just demand attention NOW. Hyperglycemia is more sneaky causing injury to various parts of out bodies that can decrease well being (understatement) or lifetime.

I am a fan of Alan Shanley who is person with type 2 diabetes living well in Australia. He has a blog that is quite good. I have never read anything on it that was in error or harmful.

The following link is to his post on hyperglycemia and how it damages people with diabetes, no matter the type.


Thanks for linking to this @CarlosLuis I just had a chance to read it.

The advice here runs counter to the advice I get from Joslin Diabetes Clinic. They are much more casual about Hyperglycemia and more concerned about Hypoglycemia. So when I tell them that I ate a bagel and went up to 280 for an hour or so, they are like “well, don’t worry about it, your A1C is below target (about 6.0).”

How to reconcile these two perspectives? I guess we’ll just have to wait 10 years and see …



Just a note on the study itself–I skimmed down to the method section at the end and if I’m reading it right, they kept these cells at low vs. high glucose concentrations for 72 hours. That makes sense if want to be sure you produce the phenomenon, but it doesn’t tell us anything about how rapidly the mechanisms they describe take to work in everyday conditions. In particular it doesn’t support the blogger’s claim that “short-term blood glucose spikes… cause immediate damage” (my emphasis). So I would not leap from this paper to any conclusion about how damaging transient hyperglycemia can be.


I apply a common-sense approach to any of my BG spikes.

  • Is a spike to 180 bad? I say - not ideal, but not as bad as a spike to 300…

  • Is a 2 hour spike bad? I say - not ideal, but not as bad as a 5 hour spike…

My approach might not stand up to scientific scrutiny, but it has served me well. And it’s a very simple approach. Try to limit both the magnitude and the duration of the spike. :man_shrugging:


And be thankful for the tools we have today to support this.

Testing urine doesn’t help much for that criteria, but all we had for many years.


This topic relates to a current issue for me that I’d been pondering today: should I get my eyes tested again before I order new glasses? My dexcom had topped 200 around the time the test was taken, yesterday. His optometry people have always seemed very good, and it was a very careful test, but would there be enough of a difference if, say, my eyeballs were a little swollen from the hyperglycemia, bg having been over 140 for at least an hour, climbing steadily upward ? (I’d evidently ignored my 130 alert, so had not correction-bolused soon enough. Both not soon enough to be effective at time of eye test and also, not realizing how quickly and far it would go, not big enough. Although, that would bring up the question if a change in bg back down would also affect the test.) Stress was no doubt one factor in the high. LOL, in both my judgment about bg and the bg behavior itself.

Lots of affects blood sugar changes seem to have on my vision, but most of what I notice are from lows: large white-out areas, little spinning white lights, trouble focusing. In the old days, when high bg was more common for me (dx in 1955: though I couldn’t test bg for about 25 years after that, I’m quite sure it was common), I did feel I just didn’t see as well when I didn’t feel in good control.

The doctor, incidentally, attributed my recent vision changes to age, didn’t think there was any diabetes connection. This was an ophthalmologist I’ve gone to for years. And, this wasn’t my retinal specialist, who, after regular tests, says that I do not currently have retinopathy. And, referred me back to the other doctor when, in a recent visit, I mentioned the current vision problems,. I’ve been stable for decades, after pan-retinal lasers in the early 1980s.