Is there a "worse" kind of high bg?

Does anyone have any insight if there is a difference between being high (over 240) due to insulin interruption vs. being high (over 240) due to a food spike? I’ve always wondered if all highs are created equal as far as our bodies’ mechanics are concerned. When I was new and on MDI and would spike when testing out different foods and timing, I worked hard to get it back down quickly…but I also figured that excess sugar in the bloodstream due to a carb surplus was not AS bad (not great though) as high blood sugar due to insulin starvation (i.e. a missed Lantus shot or whatever). In the case of carb excess, I figured my cells were still getting fuel…there was just too much leftover in the bloodstream that I needed to export ASAP.

Does this question make sense?

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I feel like being high due to lack of insulin must be worse… you’re on the road to DKA then. With any high BG that means your cells don’t have enough insulin to ferry in the sugar that’s sitting in your blood – but it’s also true that your body may not actually need that sugar if you ate a particularly large and hearty meal. But with a high BG due to missed insulin from a bad pump site, your basic bodily needs are not being met.


also it’s possible when you feel worse with a high BG due to missed insulin, you could be generating ketones, which could be part of why you feel sick.

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Glycogen synthase is one of the necessary enzymes needed for your body to take glucose from your blood and convert it into glycogen (the process called glycogenesis).

When insulin is absent, glycogen synthase is phosphorylated and inactive. Which means you neither convert glucose to glycogen (glycogenesis), nor can not get any energy from it (glycolysis).

Even with high BG, as long as you have some amount of insulin, such as basal, your body is still able to perform some amount of glycogenesis and glycolysis.

Without any insulin, your body can’t do that at all!

So, the short answer is that a high BG from no insulin is worse than a high BG from carbs where there is some insulin available.

Make sense?


I’m fairly certain that the rate of of going high may be a factor as well. I would like to know if a long slow rise over time is less damaging than a quick spike.

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I would guess it’s the opposite based on my son’s behavior…hovering slightly high (180s for 3 hours)and he starts to seem tired, pees a lot, generally grouchy. Quick spikes and he barely perceives them.

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I have the same experience with noticing more effects of an extended high rather than a quick spike.

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The one that refuses to come down. :smiley:


FWIW, diabetic CDE weighed in and said magnitude of swings has bigger impact on vascular damage down the road than steady highs (my current dilemma although it’s improving as I think for myself once again). Not sure if she was trying to make me feel better but I wanted to throw that out there.

This is apocryphal and *sounds reasonable but is not actually demonstrated. They’ve shown that people with variability in their A1C over the long-term have worse outcomes than those with steady ones – but not that the day-to-day swings in BG that we all hate so much do damage.

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Is that after properly adjusting for A1C? In other words, is there good evidence that variability in BG is an independent risk factor for long-term outcomes? I vaguely thought I’d seen that variability (after adjusting for A1C) was correlated with short-term incidents, but not long-term outcomes. But I don’t trust my recollection on that, and it could have been from a science news site rather than an actual paper, which would make my recollection even more dubious.

I thought that yes, variability in A1C was associated with long-term complications, like nephropathy:

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Same. An extended high that I can’t seem to fix is what makes me feel worse.

A drastic swing can be unpleasant, but the effect is usually temporary whereas an afternoon of high blood sugars is going to be felt until I have a chance to sleep and fully recover.

Thanks for the reference. After reading that paper I’m not prepared to give much support to their conclusion because I prefer an alternate explanation that they themselves gave in the discussion.

Here’s how that alternate explanation goes. On average, the patients in the study got 2.4 A1C measurements per year. Now I’m going to exaggerate to make my point easier to understand. Consider two patients. One has an A1C that’s about 9 every time. The other has an A1C of 11 in the first half of every year, and A1C 7 in the second half of every year. The alternate explanation points out that during each 6-month period their A1C is 11, they’re accumulating a huge amount of damage, and having an A1C of 7 for the other half of the year doesn’t make up for this. So maybe the cause of their extra risk of complications isn’t that ‘their A1C changes a lot’ it’s that ‘they have a way-high A1C for long periods of time.’

Here’s the statement from the paper that gives this alternative explanation:

“An alternative possible explanation for our data relates to the fact that the risk of microvascular complications seems to rise exponentially, rather than linearly, as A1C rises (2,3). Thus, although patients who have more variable A1C values will be spending the same time above and below their mean value as another with comparatively stable A1C, their average risk will be higher because their periods of sustained glycemia far above their mean will be placing them at an especially high complication risk, which will more than cancel out any reduction in risk resulting from them also having equal periods far below their mean. If true, it would be expected that this effect would be exaggerated as the individual’s mean A1C was higher, which may be one reason why the influence of A1C variability seems greater in conventionally treated patients.”

I don’t see where they explain any reason to prefer their original explanation over this one, so I’m not eager to accept their conclusion that “This study has shown that variability in A1C adds to the mean value in predicting microvascular complications in type 1 diabetes.” I’m not inclined to believe “variable A1C causes extra damage” because I find it easier to believe that “extended periods of really high BG cause an accumulation of non-reversible damage.”

And I would be especially reluctant to accept a “science news” summary of their data table along the lines of: “the high-variability A1C group had double the risk of microvascular complications,” because I think that misses the point. To me, extended periods of high BG cause damage, and you can’t undo that by having other extended periods of good BG.

As an aside, I’m not sure I’d draw strong conclusions from this paper in any case. The paper was from 2008, the patients were taking an average of 7 fingersticks per day, and “conventional” treatment probably meant sliding-scale insulin dosing and “intensive” treatment probably meant basal insulin plus a few (like 3 or 4) bolus/correction doses per day. The conventional cohort had an A1C of 9, and the intensive cohort had an A1C of 7. And according to the article, their A1Cs were blinded, so they couldn’t improve themselves based on seeing their own A1C.

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well we know for sure that rapid changes A1C do worsen retinopathy – so to me the idea that these fluctuations would be bad in other ways also makes sense to me.

I thought that we only knew (from DCCT) that a large drop in A1C first causes retinopathy to get worse, (but after 5 years or so of lower A1C the outcomes are increasingly better.) I wasn’t aware that it is known that a faster drop (or a rapid change) in the A1C makes this more likely or worse.

I saw from Eric’s post that the initial harm seems to be because of the drop, not the speed of the drop. Reducing your a1c too quickly - #21 by Eric

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It does seem that variability in A1c is a strange concept. I can’t imagine hopping around from 6% to 9% to 7%. Seems like you’d either be trending in one direction or hovering in the same ±.5% most of the time.

It sounds like you both, @bkh and @TiaG, agree that variability in bg has not been shown (as of yet) to be “worse” than a prolonged high bg. Is that correct?

I think you’d need CGM-based research, not A1c-based, to address this question. I imagine that’s coming down the line, but it would inevitably be correlational (i.e., is it the variability difference itself or what’s causing the variability difference that has the effect), so still hard to interpret.

yes I don’t think BG variability (day-to-day) has been shown in any robust way to cause complications. Studies that have looked at CGM data and variability have had very weak or conflicting results. And they’re all too small.

I want to be cautious in my response, because I don’t consider myself expert in the relevant literature. I’ve read a few studies, and a few more “science news” articles. I’m happy to comment on what I think a particular research paper has shown, but my opinions gleaned from the modest number of papers I’ve read are closer to rumors than facts. For instance, there’s a good chance that I’m unaware in cases where a result has been withdrawn by an author, or contradicted by a newer study, because I just haven’t read widely enough.

So, back to your question. I think we have strong evidence that average A1C over the long term predicts long term outcomes, and that in the long term, a lower A1C is better, with diminishing returns below 6.0 or so. I think there’s reasonably good evidence that whenever our BG rises above some threshold, like above 140 mg/dL or 160 mg/dL, we are accumulating damage. There’s evidence that the higher the spike, the faster the damage accumulates. But the danger of a flatline at 170 vs a spike to 250 followed by a plunge to 45? I simply don’t know, other than the fact that a deep hypo can trigger a lethal cardiac arrythmia.

I really want to conclude that a flatliner with an A1C of 7 will have better outcomes than someone who routinely spikes to 300 and overnight goes low into the 50s, but who also has an A1C of 7, because it seems like that should be true. But I don’t know the literature on that question, so I’m left guessing, without facts. We are starting to see new metrics proposed that would give some kind of number to tell where any particular CGM graph is on the spectrum from flatline to wild rollercoaster; in the future there may be research results to suggest whether flatter actually gives better outcomes.

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