From Markus Berndt: It’s one of the first recommendations you get after being diagnosed with diabetes. “Get active, do more exercise, it’s good for you!” And since we’ve been a child we’ve heard that exercise is healthy. If we do it consistently we’re rewarded, literally, with an awesome beach body.
Adding exercise into our day is also good for our diabetes. We’re taught that exercise lowers blood sugar, right? But can the opposite also be true? Can you have high blood sugar after exercise?
We now know that physical activity usually lowers blood sugar because it reduces how much insulin is needed to move sugar into the cells.
While, in the past, most experts advised frequent training intervals at moderate intensity, but recent studies have shown that even short, intense workouts are very effective. For example, a 15-minute intense weight training lowered blood sugar even more than what’s seen in some endurance training.
So activity lowers blood sugar – but not always!
Personally, I experienced this very early on and was extremely irritated! I just learned that exercise lowers blood sugar, but an intense 45-minute run consistently resulted in higher blood sugars than when I started! What in the world?
At first, I was confused and felt like I didn’t understand the world anymore. Then it was more of a “would you look at this?” kind of thing. And finally, I was determined to figure out what was happening. I knew there had to be an explanation.
Why does exercise sometimes raise blood sugar?
Exercise can trigger the body to release stress hormones, like adrenaline which stimulates the liver to release glucose or cortisol which makes you more resistant to insulin. And strenuous activity, especially competitive sports, triggers increased stress hormones, in which case blood glucose usually increases (at least temporarily).
In general, we know that different exercises affect us differently. And we also know that we’re all very unique, and the same exercise affects different people differently. Our blood sugar response will also depend on our level of physical fitness and personal exertion. Generally speaking, 30-40 minutes of running brings different results than an hour of cycling, swimming or even boxing. The intensity of the activity is often as important as the duration.
Finally, even though it can be unsettling, we must be persistent! A high blood sugar is annoying, especially after exercise. Nevertheless, exercise and activity are very good weapons against your diabetes monster and they work in your favor in the medium to long-term, even if you’re struggling against those BG boosting stress hormones in the short term.
Generally, the post-exercise blood sugar spike settles down and returns to normal after an hour or two, so check again after some time if you’re able to. And the exercise itself pays dividends for much longer than that, so the tradeoff is well worth it. However, if you notice that things aren’t moving in a good direction I recommend making an appointment with your diabetes care team to talk about it. There are many options available, and they’ll help find something that works well for you.
Good info, Markus! Thanks!