I would not call myself an athlete :), but have always been very regular with my exercise - running, other cardio, moderate weight lifting. I’ve experienced all the things you describe, and have learned how to (mostly) manage it after LOTS of trial and error. I think everyone reacts a little differently to exercise, but I have the same reaction that you do, with highs afterwards. I do have a pump and CGM, which helps make some of this easier. I will say that exercise became more of a challenge for me after going on a pump - dropping so dramatically with exercise that previously I could get through without any lows. My humble theory is that having short acting insulin in your system all the time is part of the reason for that. Anyway… I have also found that the more intense the workout is, the higher I will go afterwards. I’ll try to summarize my ‘rules’ for exercise here:
- Like someone else mentioned, I decrease my basal rate by 50% for 30-60 minutes before I exercise. This is MOST important when I’m doing any prolonged cardio (especially running), which sounds like most of what you’re doing.
- I also need to modify any bolus I take if it will be within 3-4 hours of exercising. For example, if I’m going to exercise at 5 pm, then any bolus I take from 1 pm after needs to be modified, so that I don’t have too much insulin on board. The more on board, the more dramatically I will drop during exercise (which just sucks to deal with), and then the more dramatically I will go up afterwards. I usually use about 50% of my correction factor (if I need one) and/or 50% of my bolus for whatever I’m eating during this time frame. If I need a correction factor AND I’m eating, then I usually decrease the whole dose by ~50%.
- As far as a goal BG to start exercise with, I’m usually ok if I’m at least ~120, AS LONG AS I’ve done the previous steps, to avoid having too much insulin on board when I start exercising. I’ve also found that I can start with a much lower BG when I exercise first thing in the morning (because…no recent bolus to manage…) vs. later in the day.
- I maintain my basal rate at 50% less during exercise. Sometimes, 75% less, if I think I’m more prone to dropping, based on the intensity of the exercise.
- As soon as possible after exercising, I increase my basal by 75% for 1.5 hours. THIS IS KEY FOR ME!!! It has mostly eliminated the dramatic highs I was otherwise experiencing.
- As others have said, be prepared for a drop in your BG - mine happens right around 4 hours after exercise. I either take a little less insulin with whatever I eat after exercise to try to minimize this drop, or sometimes just have a little snack around that time when I can tell that I’m dropping.
Of course what you eat in the few hours before you exercise will absolutely affect your blood sugar during exercise. Making sure to have a balance of carbs, protein, and fat can help.
Yes, so many rules and steps and details and planning! It’s frustrating, and hard to not just be able to pick up and go. It takes a lot of work and experimenting to figure it out, but you’ll get there, and you’ll figure out how your body works and what kinds of tweaks you need. Nothing can replace the benefits of exercise, especially with type 1, so keep at it. Let me know if you have any specific questions!