Physical activity of any kind is an amazing tool for blood sugar control. Exercise can have a consequence of lower your blood sugar, and will improve your body’s sensitivity to insulin. Beyond that, exercise is an amazing mood-booster, supports good sleep, the lymphatic system, and strong bones.
But, when it comes to exercise… Does it ever feel like you’re being punished for doing a good thing? Let me paint a picture for you…
You check your blood sugar and it’s 97.
You lace up your shoes, have the perfect playlist ready to go, and set out for a four mile run with your usual stash of keys and some glucose in your pocket.
Half way through, you feel your energy fading and stop to check your blood sugar.
It’s 52. UGH.
You pull out your sugar stash, down it as fast as possible before the low feeling gets any worse, and start to worry you should have brought more.
Between how weak you’re feeling and the worry of getting any lower, you end your run early and walk the rest of the way home, feeling frustrated and annoyed.
It’s been a LONG and stressful day but you’re feeling amped and ready to take on an intense workout.
You pull out your boxing gloves and hit the studio for an intense 45 minute kickboxing session. As you take out your frustrations of the day on the bag, you feel amazing, empowered, and in control.
You exit the studio, dripping with sweat, and check your blood sugar.
It’s 87. Awesome! You can probably go home and drink a smoothie after that intense workout.
Smoothie in hand, you check your blood sugar again to figure out dosing.
WHAT. THE. HECK? How did your blood sugar go from 87 to 210 in the last 30 minutes?
What is happening?
The above two scenarios have definitely represented “day in the life” scenarios for me.
It’s important to understand what is happening when our bodies behave in ways that don’t immediately make sense.
#1. Exercise can result in lower blood sugar because of the insulin you already have on board. When you are physically exerting yourself, your muscle cells need more energy. Your body goes to work, getting sugar out of your bloodstream and into your muscles. As this happens, you have less of a need for the insulin on board.
#2. Yes, blood sugar can go up during or after exercise, but it’s not because of the exercise. Instead, blood sugar can rise due to stress response and the release of hormones (like cortisol and epinephrine/adrenaline) into your bloodstream. This is much more likely to happen after a high intensity workout.
Ironically enough, once a post-workout high is resolved, the improved insulin sensitivity you get from the workout might still result in lower than expected blood sugar hours after the workout.
I get it (sort of)… Now What?
Things to know for insulin dosing:
- If you are on an insulin pump: it may help to reduce your basal insulin an hour or two before you begin a longer workout (anything over 90 minutes). If you wait to reduce until you start working out, you will have waited too long as it takes a few hours for the insulin reduction to have an impact
- If you are on shots: assuming you take just 1-2 basal insulin injections per day, it will be less helpful to reduce basal because you would be reducing for an entire 12-24 period, instead of just when working out. The exception here is if your activity level is significantly longer (for example, going on a long hike). I usually reduce my basal in scenarios like this
- When you know your body patterns, you may be able to predict when an intense workout will trigger a high. For example, when I kickbox, I compensate for that by taking a small dose of bolus insulin right after the workout.
Things to know for food:
- In many cases, food may be your best tool to prevent blood sugar lows. This is especially true when physical activity is unplanned or short in duration
- You will want to have very quick-acting sugar sources on hand, things that are convenient and easy to consume quickly when working out. My personal go-tos include:
Use exercise to your advantage:
In addition to all the obvious benefits of exercise, movement can be especially helpful when experiencing high blood sugar.
In conjunction with insulin, a 20 minute walk or 50 squats can work wonders in dropping a high blood sugar into normal range rapidly.
Exercise is also a great tool to incorporate when you know you’re headed into a scenario that will increase your insulin resistance (road trips, long flights, or any period of sustained inactivity).
Need help implementing a plan to workout with confidence? I cover approaching exercise with confidence (and so much more) in my 1:1 work with clients!
Special thanks to everything I’ve learned in Gary Scheiner’s Think Like A Pancreas for inspiring so much of my perspective on T1D + Exercise.