(Possible) False Hypo From Dexcom During Heavy Workouts

TorqPenderloin said:

Note: I'm a new type 1 diagnosed 9/2/15. I've had my Dexcom G5 for a week and a half now.

My question is about possible false hypo positives I've experienced lately.

A few things I've noticed:
-this hasn't happened during my morning workouts (5am) when I usually workout
-it's happened twice and both during evening workouts (6-8pm)
-on one occasion it went from 115mg/dl down to 65 in a matter of 15 minutes
-when I get home (5 minutes later) to do a finger test my readings are normal 100-120mg/dl

My Dexcom is otherwise accurate and I am aware of the lag (I was told 6 minutes).
It only happens during heavy lifting workouts. To put "heavy" into perspective, I'm 27 years old and a former competitive power lifter so we aren't talking about a set of ankle weights.

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I've noticed a similar thing from the Libre (on my arm) when doing heavy (patient lifting) arms sets.

I suspect that it is caused by the glycogen in the muscles local to the sensor being consumed and any interstitial fluid glucose also being consumed, but due to the nature of heavy sets (i.e. typically low reps), they don't induce a liver dump to release more glycogen as glucose to provide additional fuel.

I've noticed that when I do volume sets I can see a clear liver dump, but typically intensity doesn't lead to any noticeable change, except when doing arms as that is where the sensor is located.

TorqPenderloin said:

How do you combat the readings? Do you just trust yourself to recognize the physical hypo symptoms? Fortunately, I am VERY aware of my hypos. I start getting the shakes in the mid 70s and I lose coordination (get very clumsy) at anything below 70.

The other problem is that my girlfriend works in New York City (2400km away) so I spend most of the workweek alone which means I don't have anyone to watch out for me.

I'm worried the only answer I'll hear is "take it easier" which I'm not comfortable accepting. I'm doing everything in my power to keep my quality of the life the same (or better)since being diagnosed.

Thanks for the thorough reply,
Mark

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Mostly I ignore them. I too have decent hypo awareness, so it isn't really an issue.

The best mechanism is to ensure that you know how your body works via observation. For me this means checking before I start training (again, not usually a finger prick, just using the Libre) and then it's worth checking when you are seeing the low warning on the Dexcom, just to reassure yourself. I'd recommend that you carry blood testing gear with you at all times - while the Dexcom is very good, it can (as you have seen) produce false data.

You'll soon learn the pattern of what activity does what to your glucose levels, and thus learn the best way of dealing with them. What it comes down to is observe, document, review. The patterns usually become fairly obvious and then it's how you choose to deal with them.

In terms of spending the time alone, my view is that you should live your life anyway, so learn how everything works. The reality is that most of what you do will have some level of pattern to it, and it's making sure that you understand how these patterns work and when you get an observation outside of them that is the critical aspect to your life. There is certainly no need to give up doing something you enjoy, and as far as I and many others are concerned, take it easier isn't an option that we choose to take.

I get this when I do tricep dips (I wear it in the back of my arm). Or if I spar. I think the impact affects it. I like the science tho tim.

Mrs Vimes said:

I get this when I do tricep dips (I wear it in the back of my arm). Or if I spar. I think the impact affects it. I like the science tho tim.

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The reason I don't think it's impact is that none of the things I'm doing involve an impact or pressure...

Although as you say, if you were to do Scott Curls on a preacher stool, you would be putting pressure on and could also see false lows there as the interstitial fluid is forced away from the sensor.

Your explanation is so much better than mine 'tricep dips f@@ks up me sensor' - I explained to the trainer when the alarm wouldn't stop going off.

tim2000s said:

I've noticed a similar thing from the Libre (on my arm) when doing heavy (patient lifting) arms sets.

I suspect that it is caused by the glycogen in the muscles local to the sensor being consumed and any interstitial fluid glucose also being consumed, but due to the nature of heavy sets (i.e. typically low reps), they don't induce a liver dump to release more glycogen as glucose to provide additional fuel.

I've noticed that when I do volume sets I can see a clear liver dump, but typically intensity doesn't lead to any noticeable change, except when doing arms as that is where the sensor is located.

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I suspect you are right in the local effect and local depletion happening quicker than the liver dump and lag of the sensor.

Back to the OP, that change (100-65) would be more like what I see during aerobic exercise with excess insulin circulating. I don't do any heavy weights like that any more, but with both yoga and the more moderate weights sets I do, I make no adjustment to insulin and generally see BG flat or slightly increasing.

TorqPenderloin said:

How do you combat the readings? Do you just trust yourself to recognize the physical hypo symptoms? Fortunately, I am VERY aware of my hypos. I start getting the shakes in the mid 70s and I lose coordination (get very clumsy) at anything below 70.

The other problem is that my girlfriend works in New York City (2400km away) so I spend most of the workweek alone which means I don't have anyone to watch out for me.

I'm worried the only answer I'll hear is "take it easier" which I'm not comfortable accepting. I'm doing everything in my power to keep my quality of the life the same (or better)since being diagnosed.

Thanks for the thorough reply,
Mark

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My view - give T1 a kick in the nuts as often as you can. You're in charge not it, you seem to be taking that attitude already and I would only encourage it. If we let it this condition has the potential to rule our lives and reduce the quality of that life.