Continuous Glucose Monitoring

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.

Rather than show that such exercise is unhealthy, I think it simply shows you need to consume some glucose during.

There's a reason aside from taste that sports drinks all contain a helping of glucose. I can't recall if I saw them in the US but in Europe many supermarkets offer products like "Dextro Energy", which is essentially just a sugar tablet advertised to people who need glucose during sports.

this, 100% i've been running 35km while fasted for 36 hours, and it is way more difficult than when you allow yourself to eat a snickers on the way.

now i am running my weekly half-marathons with something sweet, and it has been awesome. Like really no big deal.

As sibling comments stated, that's why you see recommendations to eat during longer exercise sessions. A common recommendation I've seen is that for an hour or less of activity your internal stores should suffice, but for more than an hour 30-90 grams of (probably easy-to-digest) carbs per hour of exercise is recommended.

Stupid question (layman). If it drops below 80 mg/fl, are there not mechanisms in the body to increase it? i.e. shouldn't the liver dump glucose into the blood stream to compensate? Failing that, shouldn't hormones be activated to cause fat be broken down into energy?

My understanding is that type 2 diabetes (which I am) are bad at _maintaining_ glucose level, both lowering it when it's high and rise it when it's low.

Taking medicines that aim at lowering the glucose level may also contribute to hypoglycemia from time to time.

Makes sense. I was wondering what the mechanisms for non T2D.

When I'm working in the gym (cardio and weight lifting), I purposes train till I feel completely drained and pretty week. I'm hoping there's nothing wrong with that.

The liver does do this with a substance called glycogen. It’s called counter regulation. It has a store of glycogen, which it will release into the blood stream if BG drops too low. It is a finite store though, so if you exercise a lot (or overdose on insulin) you can metabolize most of it.

In this case, hypos will become more severe and happen easier.

Also, the store will be replenished by pulling excess glucose out of the blood over a period of roughly 24 hours after exercise or the hypo. So exercise has a beneficial effect of keeping BG lower for some time. That’s also why you should eat a little more and carbs after heavy exercise.