Checking Blood Glucose Before and After Workouts

Shelby Kinnaird and niece Claire

Me and Claire

The good news: I have a brand-new niece! Claire was born on December 14th and I was able to be there and spend the first two weeks of her life with her and her brothers. The bad news: I gained about four pounds while I was gone.

Before I left town, I attended a local diabetes support group meeting and the topic was fitness. A personal trainer gave a wonderful presentation about diabetes and exercise. The most important thing she mentioned was that you should check your blood glucose (BG) before and after workouts. I’d never thought of doing this before, but it makes perfect sense.

It’s been months since I went to the gym. I take occasional walks, but I’ve really been ignoring exercise. I got back on track today (before the New Year’s rush) and decided to check my BG pre- and post-workout. Before my workout, it was 116 mg/dL. I consulted my handy dandy cheat sheet (see below) and realized I should have a snack of 15-30g carb before hitting the treadmill. I gulped down a nutrition bar (210 calories, 7g fat, 22g carb and 15g protein) and headed to the gym. I walked on the treadmill for 30 minutes, did some stretching and other exercises (situps, pushups, yoga poses). When I got home, my BG was 94. So even with a 200+ calorie snack, my BG went down. I guess there’s really something to this exercise thing!

If you have diabetes and are beginning to exercise, I recommend checking your BG before and after workouts. Here are the guidelines we were given at our support group meeting, but please check with your doctor to see if these will work for you.

If your blood glucose is this BEFORE exercising: Do this:
< 100 mg/dL Do not exercise! Have a snack containing 30-50g carb, check BG again in 25 minutes.
100 – 180 mg/dL Have a snack containing 15-30g carb, then exercise.
181 – 250 mg/dL Exercise.
> 251 mg/dL Do not exercise! Drink water and check BG later. Once you get in the 181 – 250 mg/dL range, do very low intensity exercise.
If your blood glucose is this AFTER exercising: Do this:
< 100 mg/dL Drink water. Have a snack containing 30-50g carb.
100 – 180 mg/dL Drink water. Have a snack containing 15-30g carb.
181 – 250 mg/dL Drink water.
> 251 mg/dL Drink water.


  1. Sandy says

    Thank you for this information and the chart. I was diagnosed with Type 2 just about a year ago and have been managing well with diet, but have not been exercising. This gives me something to go by. I knew exercise was important, but every time I did, my BG would drop really low. Thanks for a great blog! Looking forward to reading the archives and checking out some new recipes!

  2. diabeticFoodie says

    Welcome, Sandy! I haven’t been exercising much either, but I’m trying to change that. It was really an eye-opener for me to hear that you should check BG before and after workouts. I wasn’t at all hungry the first time I checked my BG before a workout, but I was in the range to have a snack, so I did. Given how much my BG dropped afterwards, I’m really glad I did!

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