Background insulin when exercising

Hello. Am currently training for a marathon, my long runs now three hours in the hills. I don’t want a pump (please don’t try to change my mind). I run with 16 units Lantus as background, no Humalog at all unless I get high during a run, which is rare. The big problem is the lows. I try to begin at 150, then constantly ingest sweets to keep it there. Here comes the question…if I go lower than 16, I seem to lack energy, even w/normal BG. I assume that my body needs some insulin to convert that BG to energy. Yet it seems the accepted practice for pump wearers is to drastically reduce the basal beforehand, sometimes shutting the pump off when excerising hard. So, either I am very different, or I’m confused. Maybe both. But I can say that I have no rebounds after exercising. I do suffer from hypoglycemic unawareness, so I test BG every 20 minutews or so when running. I can say that my insurance company hates me. :slight_smile: Anyway, the marathon is less than a month away, my training is going pretty well (most days), and I’m almost ready. Advice appreciated. Howard.

You do need a certain level of continuous background insulin to have any energy (a non-Diabetic never turns off their pancreas completely). That’s probably why you lack energy if you drop below 16 units Lantus. The difference between a pump user (not trying to convince, just explain) and someone using Lantus, is that a pump user can decrease their background insulin level for ONLY the time around their run. For example, on a long run (e.g. 2 hours) I’ll lower my basal to 25% for 2.5 total hours, starting 1.5 hours before the run and ending 1/2 way through the run). Since the quick acting insulin takes about 2 hours to be absorbed and really be effecting the background insulin level, this regime keeps my level low during the run and the level starts rising back up to normal toward the end of the run. I found that ingesting about 20 g carbs every 25 minutes (I use GU) is about the rate I need to keep from going low.

In your situation, if you drop the lantus below 16, your entire day (or 1/2 day if you have a split dosage) is at a reduced insulin level (which could explain the low energy). If you haven’t already tried it, you might consider a split dose of lantus. Possibly something like 9 units 18 hours before you typically run and then 7 units 6 hours before you typically run.

Ken, thank you for a very helpful reply. This particular problem I’m having, i.e., dropping background insulin for the run w/o dropping it too much several hours prior to the run, sounds like a challenge a pump might help me meet. I never said I will never try a pump, I’m just not ready yet. I mean, my A1Cs are 5.3, so I’m doing most thing s pretty well. If I start a long run at seven a.m., I am typically awake no later than 6 am, so in the scenario you outlined, I would still have enuf coverage to prevent dawn phenomena??? That happens to me only rarely, but often enuf to be considered. For now, your suggesting that way to split the Lantus is certainly worth trying, but I will wait til after the mararthon to experiment, as I am only two weeks out. I think I am doing fairly well, but always trying to make things better. Re: CGM, interesting, but as things are now, a 15 minute old BG reading would not be nearly as helpful as a current one. MY BGs tend to not be terribly stable on my long runs, but, of course, that might be a factor of not having a pump, but I think the main reason is that my long runs are in the hills, hence there are drastic swings in energy used. I did a half marathon five months ago on a fairly flat course, and painted what I consider my masterpiece up til now, started at 170, kept it betweebn 120 and 160 all the way. Not fast, mind you, but slow and steady. But that brings me to my other big challenge–unpredictability. Before the half, I awoke around 100 BG, then, about twenty minutes before the start, I had some diluted OJ and one fig bar, that got me to 170, and it never went higher. The frustrating thing is I might repeat all that five days later, and have a BG of 230 a few miles into the run, rather than 150. Because of a terrible (and well-founded) fear of high BG, I probably tend to eat less than I should prior to the long runs. Thanks again, Ken, more comments from you or others will be appreciated.

Actually, the 15 minute delayed BG is pretty useful. It’s plotted on a trend-line so you can see if you’re rising, flat, or dropping. I don’t even carry my glucometer with me on long runs. I watch for the BG to go flat or the rise to slow down, then I know it’s about time to consume more glucose. Since I don’t run when there’s a risk of a large insulin bolus peaking, my BG won’t change more than about 50 max over a 15 minute period. So by watching the trend line I can generally keep things between 90 & 140 (occasionally outside that range).

But I agree with you absolutely. 2 weeks before a marathon isn’t the time to make any big changes to your regime. Good luck on your run.

Howard - what Ken said.

I hope the marathon went well. Did it? How’d the BG do?

As a pump user and marathoner, I am able to have a little ‘finer’ control over my background insulin on long runs than you are, I think. You might look for some advice in Sheri Colberg’s book “the Diabetic Athlete.”

If you are not experiencing lows on the run, there’s not any reason to adjust your Lantus. If you were to adjust it at I would consider a calculation like this: 16/24 hours= .66 units lantus/hr. Multiply the hours you are going to run by .66. so if you will run 2 hours, the number is 1.33 units. You can then reduce your 16 unit dose by that amount or a fraction of that amount - say 50%, or .65 units.

I eat lots of carbs DURING a long run, not before, not after. I hydrate with a 50-50 mix of water and Gatorade. I try to start with a slightly elevated BG, up to 200 and test frequently. Ken’s advice about focusing on the trends on the CGM, if you get one, is spot on. Pay no attention to the number, just the trend. Short of that, frequent testing is the best we can do. I carry a One-Touch Mini on all my runs - very convenient and unobtrusive.

So, get the book and once again - how was the marathon? Which one was it?


Thanks for all that useful advice, and here is the update. On Oct. 12, I ran the Bizz Johnson trail marathon in NE California–had a tough time w/regulating BG–too low, too high, too low, all day long. I find it so frustrating that the exact regime that works one day doesn’t the next. The best I can say is that I did finish, but was terribly disappointed. I sort of dragged myself across the finish line. It was my first marathon in 25 years, and I had trained hard for eight months. So, feeling the need to “redeem myself” and throwing caution to the wind, I ran another the next week, Humboldt Redwoods marathon, also in northern California. Much, much better, started w/BG @ 150, tested and ate glucose and ERG every two miles, and never went below 130 or over 200. BG was 99 at the finish. I am not fast, really more of a plodder, slow and steady, finished in 4:54, which was slower than my goal, but perhaps my goal was unrealistic. My energy was good all the way, even during the last six, when I was actually passing people!!! I am 54 years old, and, while not old, am not a kid anymore. I have had diabetes for 41 years. I am terribly hard on myself for being so slow, but my friends all think I did great, so maybe I did. I’m going to take it easy for a few weeks, then try to come up w/another goal. It seems as though I need a race in the future to push myself to go long on Saturday morning. Again, thanks for help. Howard.

!! you ran a marathon in under five hours WITHIN A WEEK of running an earlier marathon!!!

God, what a wimp. :slight_smile:

Howard, don’t be so hard on yourself. I ran a marathon in under five hours but it was ONE YEAR after my last marathon!!!

Good job.