Exercise + changing insulins = highs and lows

Last Friday, I started a modest workout plan at my local YMCA through their "PFP (Personal Fitness Program) that’s designed for people who haven’t worked out in a long time if ever. It started with a fitness assessment and a meeting with a trainer to set up a weekly workout. Each week, I’ll meet with the trainer again to adjust my workouts.

On Tuesday, I switched from Humalog to Novalog in my OmniPod (because the copays are so different that I’ll save over $600/year under my new insurance plan). I’d read that Novalog acts faster than Humalog and that it’s likely to need less Novalog, too.

I changed my basal rate by decreasing it 25% when I switched to Novalog last night (Tuesday). This morning, I woke up at 216 (usually at 90 when on Humalog). I gave myself a correction bolus (which I did not change when I switched to Novalog) and then ate my breakfast, using my new IC ratio. About 45 minutes after eating, I went to the Y for my workout. Right now the workout is 5 minutes on the exercise bike, 20 minutes on the treadmill, and as long as I can on the elliptical (so far, one minute!) plus some stretching at the end.

When I got home about 45 minutes after the workout, my BG was 50.

My diabetes educator said to decrease my basal rate by 25% when I exercise and keep it there for two hours afterwards. I didn’t do that this time because I wanted to see what would happen with the change to Novalog.

Based on your experiences, do you think it was the correction bolus (since I hadn’t adjusted the correction factor) or the fact that I didn’t decrease the basal rate?

I know, I know. I need to keep testing my BG and I will. Just hoping that I can benefit from your experiences and wisdom, too. :slight_smile:


Hi Janet
The low that happen to you last morning happens to many people. In my opinion reduce your basal 25% for making exercise its OK, for a period of time around 2 hours, also applying a correction bolus its OK.

My recommendation its to also apply a reduction to your correction bolus of 1 or 2 units if you plan to make exercise at the moment you get a correction bolus. Remember that aerobic exercise have a tremendous impact reducing blood sugars check your sugar every hour after for 2 hours, and see how your body reacts to excersise and correction boluses.

Other option if your sugar its around 200 its do not to use a correction bolus and just walk for and hour. Check you BG and you would see probably a normal BG level just with your basal insulin effect. Avoid extreme workout some time moderate for and hour its very good to low blow sugar and exercise with a good cardiovascular effect

Good look !

You should also decrease your basal rate by 25% an 1 to 1.5 hours before you work out. you have to rember the insulin that you took at lets say 8:00am is working at full force at around 8:45am. What i would do if i was going to work out at 9:00am i would reduce my rate by 25% at 8:00am and run that till the end of my work out. i would then check every hour for the next 2 to 3 and make any corections that are needed.

Hope this helps.


Do you also reduce your basal rate for a while after you exercise? If so, by how much?

Thanks for your tips – you, too, Hector.


It depends on how long i have exercied for. if i am going to the gym to do a 30 min weight workout i don’t but the days that i do cardo 1h+ i keep it reduced for about 30min and drink about 1/2 a cup of milk.
Hope this helps