Basal Rates and Exercise

I am having an impossible time figuring out the factors I need to consider when I get ready to work out and not having any low blood sugars!

I have an Animas 2020 and I’m assuming most pumps have the feature that mine has, as far as the ability to set a temporary basal so you don’t go low during activites. My question is - what are your “guidelines” for how to set your basal during workouts?

If I test before my workout, and my pump tells me to bolus - do I bolus the amount and hope I don’t go low? Or do I bolus the amount and then reduce my basal? If so, how what percentage do I lower my basal? And for how many hours? What if I want to work out spontaneously and not at a set hour? I ask that because I was told to begin reducing my basal rate at least 1/2 an hour before I work out - is this what you practice??

As you can see, I am totally confused on this. Today, my bs was 199 before I went to a 45 minute class and I took the recommended bolus, minus 1 unit because I didn’t want to go low. I begin my workout and 1/2 way into I tested - I was 299! This was very discouraging and I don’t know what to do.

I am waiting to speak with my educator next week, but in the meatime, I just wanted some feedback on what YOU, loyal question-reader, would do. Thanks!

I’m having the same problems right now. I talked with my doctor, but what he said didn’t help me much. I ended up spiking my blood sugars just to exercise. Which I hate. I am going to talk with my CDE on Monday. I hope she has some suggestions for me. I will let you know if she tells me anything new.
Basically what my doctor said was to temp basal at 0.05 units per hour about 2 hours before I go work out and then drink juice about an hour before. It really messed me up. I ended up going into the workout at 158 and coming out 215!
This is very frustrating.

Yeah, I’ve been tempted just to get myself at about 150-170 and then working out. But, then I’m afraid I’m going to go high and I hate interrupting my class to test.

I hope your CDE can give you some more helpful info. Please share if you get it. :slight_smile:

Hey, I do not do any temp basals or disconnect. I test right before I exercise, when I feel symptoms, 30 minutes into exercise, 60 minutes into exercise, and then when I am finished. If I test below 110, I eat 10g of a high protein balance bar. If I test below 85, I eat 8g glucose tabs. I keep my meter with me and a small zip lock bag with 2 balance bars and a roll of glucose tabs. Most days I stay between 80-120. I’m on the continuous glucose monitor and don’t expect to get any low alarms even if your blood sugar is low because of the terrible lag time. Don’t ask me about skiing…look at my previous post and see my frustrations! Hope this helps. Test often, know where you were and where you are going, and always have supplies around. I feel totally confident starting a workout at 100 and ending at 120. Of course, there are off days with exercise, it’s just part of being diabetic.

I worry about not doing a temp basal because usually when I’m working out, I don’t feel low - too much adrenaline is going. I’ve gone as low as 40 while exercising and only tested because I was done with my workout - I didn’t feel low at all. Normally, I test right before I work out, if I feel symptoms I will stop and test and I test as soon as I’m done.

What would your course of action be if you tested at say, 175 before a workout? My pump would tell me to bolus x amount of units - would you just then workout as normal or would you worry about getting low?

Thanks - I appreciate the tips!

I would give myself my normal amount the bolus wizard says, then eat at least 20g of carbs. I’m not worried about gaining weight because I’m fit, so I would rather have the calories when I’m working out. I fought it for years but have decided eating works best for me.

Get a copy of either “Pumping Insulin” by John Walsh or “the Diabetic Athlete” by sheri colberg for some good guidelines.

There is no one answer for any athlete. You’re going to have to experiment and find what works for you by trial and error. Here are some things to know and then I’ll tell you what works for me.

Remember that non-diabetics do not turn off their pancreas’ before they exercise, therefore turning off the pump it not a good option. Since insulin does reach its peak for about 2 hours after it is administered, turning off the pump is not going to effectively reduce your basal until two hours later, by which time you are NOT exercising, most likely. The same is true for reducing your basal - the reduction doesn’t take affect immediately. This is why it is recommended to reduce your basal starting about one hour before you start exercise.

Exercise sometimes does result in BGs going UP. I’m not sure I can describe how this works, but you might read here ( or here ( Exercise can make your liver increase glucose production. Even though exercise may make your muscles more receptive to insulin, if you have little insulin on board when you start, your BG readings can rise. Everyone’s mileage varies - that’s why frequent testing during exercise is a good idea. I test about every 30 minutes.

As far as how I handle basal rates, bolus’, food and exercise, it’s like this and it’s pretty close to what Kate does:

  1. I don’t bolus before exercise unless I’m also eating something. In that case I calculate my bolus and reduce it by one unit. If I’m not eating, I don’t take a correction bolus. In fact, I prefer to start with my BG’s a little high. Therefore, if I was starting at 175 before exercise and not eating, I wouldn’t take any bolus. If I was eating I’d calculate a bolus and reduce by 1 unit.

  2. If I’m exercising more than one hour, I reduce my basal starting one hour before I start and set the duration of the reduction to the end of my planned exercise. I was reducing by 50%, but started going low. Now I’m working at a 20% reduction. I may also be adjusting the length of the temporary basal depending on how things go.

  3. I always have a test kit with me and some glucose tabs. (the Lifescan ultra-mini, which you can get for free, is great for this - especially if you already use a lifescan meter) I test every 30-40 minutes. On long runs I bring lots of carbs with me - sports drinks, gels and glucose tabs, and use them liberally. This is also a matter of trial and error. At first I was taking in too much carbs and had high BGs during exercise. Now I’m keeping my BGs level by consuming at a steady rate to restore the carbs I’m burning up but without going high.

  4. You may never find the perfect mix that works every single time, but you can find one that works for you most of the time by trying different things and being cautious about going lows.

  5. Always, always, ALWAYS keep a testing kit with you, test often and Keep Some Glucose Handy.

  6. A CGM is helpful to let you know if you are going up or going down, but don’t count on the number to be accurate. As Kate mentions there’s a lag time and by the time the CGM reads 80 you may be at 50, or lower.

Good luck,


Hi Katrina–I find my exercise lows happen if I cover a meal with a full bolus fairly soon before exercise. I have to halve the bolus to avoid a low. For me, moderate exercise (stationary bike) requires a 50% basal rate starting at exercise and for intensive exercise like running or an elliptical trainer, a 10% rate a half-hour before, during and half-hour after. I’ve done a fair amount of experimentation (and still am) to get it right. It’s worth it since exercise keeps me in the best control!