Tune basal or carb up before exercise?

The basal bolus settings have always been challenging for me.

I was wondering for those work train, exercise intensely…would it work better for you to juice or carb up before a workout instead of trying to fine tune the basal to a perfect setting? I find that on the days that I’m more active than others, there is a lag time, perhaps for a day. The day after I exercise, I have lower BG numbers. But I simply don’t have the “energy” to be changing my basal settings because I’m likely to forget. I want to Keep It Simple. We, as a group, probably engage in more counting (carb, ICR, insulin time of injection…etc), prep work before and after a meal than any group of people. It also occurred to me that we must be an incredibly disciplined, thoughtful, and intelligent subset of people. If anything, being a well controlled PWD ought to be a positive criteria in employment consideration.


There are two basic ways of staying flat during exercise. Carbing up before you start is not one of them.

It is okay to take in some carbs before, but if you try to take enough to sustain your entire workout - and take it all before beginning - it is very difficult to get the right amount. When you carb up before, generally your BG will rise and then either stay high, or fall.

The two general methods are either feeding your basal, or adjusting your basal to the correct level before and during. Both have benefits and drawbacks.

If you feed the basal:
You just keep your normal basal and take in the right amount of carbs as needed throughout the exercise. But you need to keep a close eye on it, testing often, and be disciplined to eat just what is needed to keep from rising or falling. You basically graze on a fast-acting carb source throughout the exercise. Not too little, not too much. You keep feeding that basal the correct amount.

If you use basal adjustments:
It takes a lot of practice to figure out how much to adjust - how long before your exercise that you need to lower or stop your basal, and what percentage. And also the percentage to adjust during exercise. The benefit is when you get it correct, you don’t need to eat. The lower basal and the exercise cancel each other out and you stay level.

You can do it either way. Try them both and see which you prefer. It also depends on the type of exercise. For some exercise it is not easy to feed continuously.

But I would not recommend trying to cover all the carbs before you start your exercise.


I’m learning this too…

Right now I feed the basal (running, a gu every 5miles or so as long as intensity is low enough that my stomach still functions).

I also find I need to reduce basal the next day. I take lantus at night so the evening of a marathon or long run, I’ve been reducing basal by 10%.

I’ve done the same adjustment the night before, but I still end up feeding the basal so as I remember, I’ll experiment with cutting it by more. I need something that doesn’t require me to eat so much because this works for long runs but for races, I can’t eat so much at a higher intensity.

My normal level of exercise is fairly high so my normal basal take into account ~90min of exercise. 2+ days off I have to increase it. I have a lot of work to go on adjusting for super long days and race days.


I have the problem of getting irregular exercise. Some activities, like mowing, are on a more regular schedule and I have a temporary preset for that. Yoga classes have somewhat variable mixes of strength training and aerobic (flow sequences) so I am never quite sure what to do with my basal. But walking and such tends to be reactive for me (get BG down quick) or ad hoc (a friend calls and wants to walk or whack golf balls). Obviously I am not an athlete!! :stuck_out_tongue_winking_eye:


i experience the exact same reaction to walking; and it doesn’t mean i am walking briskly, either. just a little walk for 1/2 an hour or so, i need to be prepared with a lower basal (set about 1.5 hours before my walk) and carrying juice and Gtabs with me. sometimes even just going to the grocery store requires some prep work :wink:


Thanks for pointing this out. Exercise that is not planned is a “feed the basal” activity rather than a well-planned basal adjustment.


this is what is happening to me right now as i am writing this. my husband and i want to go have burger, guacamole and fries and chips, but my BG is 70 and i know that walking out my front door would lower my BG. i just drank a large glass of juice and instead of rising, i am going down (this is probably due to the defective MM infusion set, though).

what a Fing bummer. just waiting for my BGs to come up so we can enjoy the rest of our day :disappointed_relieved:


This gives you very little room to drop, though.

We like to be under 100 in daily life if we can. But, for sports, we like to go up to 130-140 right when we start exercise (say, feeding 15 minutes before). Then we graze as we go, using very frequent checks.

We have found that it is useless to try to ride a previous meal that is 1 or 2 hours behind, btw (i.e. undercorrecting the previous meal). When we tried, our seemingly higher BG collapsed in 5-10 minutes.


When I was on MDI I didn’t even try to adjust my basal for exercise and relied almost exclusively on carbs to balance my BG out and reducing bolus amounts. Going on a pump and CGM helped a ton! I can reduce my basal in the hour before the run and depending on how far I’m going I can set a reduced temp basal or suspend and disconnect. If I resume normal basal 15 or so minutes before ending, my post-exercise high doesn’t seem so bad. I’m still experimenting with this to optimize the timing.

Usually I have a snack with some fiber & protein to get up to 140-150 before starting out if it is going to be more than 30 minutes, and I usually need some carbs every 5 miles or so like Carolyn. I did a 10 miler today with a krispy kreme donut and no bolus beforehand (not my usual snack, but there was only one left :slight_smile: and was kind of surprised to stay around 120 almost the whole run with a gu halfway through.

I guess my bottom line is that I think a pump makes it a lot easier to manage your BG with exercise.


Whether you feed the basal or bolus, make sure to eat enough. Eric and I were discussing marathon training and since I’ve been forced to eat more while running feeding the basal, I’ve noticed I recover better from my long runs. If the activity is more than 90min, its beneficial to eat during activity for recovery even if that perfect flat line is going to get messed up. I was an athlete long before all this diabetes stuff, so I think about fueling and recovering from the activity first and the blood sugar second.

I do want to find a balance where I cut back my basal to a point so I won’t get in trouble fast if/when my stomach stops, but I also don’t want to have to think too much about micro-bolusing and constantly correcting highs while racing a marathon. Even without cutting basal, if its a race, I can get huge adrenaline spikes. Spikes = cramps for me.


Or maybe it should be a negative consideration, given the amount of time and effort we put into achieving that control (then the time we spend on this forum figuring out ways to optimize … :slight_smile:


I Love This!!! we are so disciplined…at least the members on our site.!!!


New to the site, but have done several half marathons and sprint triathlons. For almost all of my workouts, I use a temp basal that starts one hour prior to exercise (65%) and ends approximately 20-30 minutes before the workout is scheduled to end. No fueling during workouts for me unless I find myself running low, which rarely happens. I follow a low carb diet and am not working out to set PRs constantly but rather just working out to stay healthy. I low the flexibility of being fat adapted rather than fueling on a schedule like I used to do. Before going low carb, I would ingest 20-30 carbs every hour with a temp basal.


That’s what I did too.

Last year I was on MDI for all my sports seasons. Swimming is my hardest sport. I dropped very fast becasue i did not adjust basal: I dropped about 70 every 20 minutes, which means that for me I needed 15 carbs for every 20 minutes of swimming to stay even: so i would check my BG every 20 minutes and eat 15 carbs every 20 minutes. But I hardly ever ran low after swimming.

For my other sports, though, such as soccer, I did not need to eat a lot of carbs to stay up during practice (maybe 20 carbs for a whole game, plus some carbs to go up before the game). But I ran low after most games and practices, even though I bring milk to my practices, drink a bunch of it right after practice, and eat a high carb meal 45 minutes after practice.

So my eating carbs during swimming was very helpful to avoid A low after practice. But this year I am on the pump, so it will be harder to avoid a low after swimming practice.


I usually find that swim practice spikes me (I go from 100-150 or so) since its just an hour and lots of intervals. BUT we just had an easier practice and I dropped a lot. Like 130-50 in an hour so not as bad as you but I wasn’t expecting it. I swim 2-3 1 hour masters practices per week now. Not the 12-15 hours a week like I did in high school, so its different.