Extreme hypos hours after running

[jones_48]

Hi All,
I’m type 1 on a closed loop pump system (Tandem TSlim with dexcom G6). I’ve recently started running 3 - 4 miles, 2 or 3 times a week. This has coincided with some scary hypos (BS dropping rapidly and feeling awful, down to low 2s).
The hypos happen at random and unpredictable times, sometimes hours or days after a run. It’s really causing me hypo anxiety and makes me want to run high all the time.

Has anyone else experienced this and how do you handle it? I’m used to exercise and can cycle 50 miles without any issues, and I don’t want the diabetes to stop me from running. Any advice much appreciated.
(I have spoken to my diabetic nurse who said to reduce my daily basal and correction factor but it hasn’t helped).

Thanks!

 

[SimonP78]

Is there absolutely no link you can determine? What days are you running on (and/or is it every other day, back to back, just across the weekend, etc.)? As you probably know you will have increased insulin sensitivity for up to ~48h after intense exercise, tapering back to normal. As you become used to the exercise this effect will reduce (and also probably one just tends to adjust all doses/eating to account for ongoing higher insulin sensitivity.)

If a given bout of exercise isn't enough to trigger noticeable insulin sensitivity you may find that repeated sets of exercise will indeed do this, which may cause some of the unpredictability as the effects stack up and then you notice it all of a sudden when you run low overnight.

Even if you can happily ride 50 miles without any after effects on insulin sensitivity, if you've not done it for some time, the next time you do, it will still have an effect - I'd not ridden much for a few weeks due to illness/time constraints/etc. and even my 40km commute round trip was enough to give me noticeable insulin sensitivity when I restarted. The effect went away very quickly and I don't notice anything any more, though I do probably eat more and have less spikey BG so I probably have constantly (at least slightly) higher insulin sensitivity because I'm back to riding most days.

Also, running and riding don't using the same muscles, so you will probably get a response from the running irrespective of whether or not you are also riding and used to it.

I would have thought that reducing basal and reducing your correction factor should do the job - what were they and what did you reduce them to? Perhaps it's a case of needing to reduce the basal further, or are you concerned that you're sometimes running higher if you do this?

 

[jones_48]

Hi Simon,

Nope no link that I can see. These are the main hypos and the time since running:
1st: 2 days (24+ hrs)
2nd: 4 hours
3rd: 24 hours
4th: 48 hours
5th: 6 hours

I tend to run Monday, Thursday, Saturday.
Yes I noticed too when I was cycling a lot, I had less spikes and more insulin sensitivity, but nothing like the running is doing. I’m hoping my body will get used to it.

My average basal was 0.4/hour now 0.3/hour. Correction was 1:3 now 1:3.5. Also changed carb ratios from 1:10 to 1:12 and it’s helped overall but doesn’t stop the sudden dramatic drops in BS.

 

[SimonP78]

What times of day do they happen? Is it completely random, or is it e.g. overnight or when you've eaten and done a reasonable dose for food?

I find my insulin sensitivity changes quite drastically based on what I've done, but I'm never quite sure how much of an effect I will get - in the warmer months I'm riding at least 200km a week, but my riding can be somewhat variable from day to day and weekend to weekend due to childcare/work commitments, so I'm never quite sure how large an effect I will get.

I tend to counter this by splitting my evening bolus injection, which need to do anyway as this is my large meal of the day and I want to be vaguely stable on the way to bed. During the day I tend to take normal bolus (unless I've just exercised or will need to do so while it's still active, in which case I cut it) and work on the assumption that I may need a mid-morning/afternoon snack (takes me back to the majority of my life spent on old insulins with reasonably fixed eating times and quantities - nostalgia perhaps )

I'm always hungry so eating uncovered snacks is no hardship, if I don't need them (for BG purposes) I will probably take a bit of extra bolus (based on response of the previous meal) so I can eat anyway

With a pump you can presumably change the delivery shape of your insulin - what do you currently use?

I do reduce basal if I've done or am doing a long ride, but I also have a gut feeling for when I need to do this which tends to work. I also split basal (MDI) to avoid running low overnight and to tune for exercise - you have even more flexibility on a pump. If your hypos are overnight I assume you've tried setting a higher target BG level for these periods?

As I'm MDI I'm afraid I don't really know much practically about pumps (and even less about the specifics of closed loop on a given model) but what is your BG setpoint during the day and night (I guess you run different ones?) Does the pump adaptively measure and change its insulin sensitivity values or is this a thing you have to do manually (or are you intervening to override whatever it has decided?)

I'm guessing there must be people on here who do know about pumps and also your specific one, certainly I see more talk about pumps and exercise settings on diabetes.org.uk forum, which might be another avenue for questions.

Sorry it's not a very useful response, but don't give up!

 

[Melgar]

@jones_48 I’m going to jump in here, as I was a competitive long distance runner I learnt a bit about energy management. I can’t talk about how you manage your insulin as I’m on oral meds not insulin. But here is my take on what is going on.
@SimonP78 already mentioned increased insulin sensitivity. Exercise promotes increased insulin sensitivity in your muscles. Along with increased insulin sensitivity, I think another consideration is your glycogen storage. I think you are decreasing your glycogen storage levels. So glycogen is the name given to the stored form of glucose. Glycogen is found in both the liver and muscles, it’s what your body primarily uses for energy during exercise. So when you are exercising, you are drawing from stored glycogen in your muscles and liver. Once this stored form of glycogen decreases your body must replenish these glycogen stores during exercise. To do this your body will draw it from blood glucose in your blood stream. Hypo risk.

As mentioned, exercise increases insulin sensitivity. So the rate at which you use insulin increases during exercise. That is also a consideration.

Different forms of exercise utilizes muscle glycogen at different rates. So a short sprint would draw glycogen from your muscles very quickly. Sprinting is energy intensive. Where a longer run, which by its very nature, would draw glycogen more slowly but for a longer period of time thereby the body would utilize muscle glycogen and it would utilize stored liver glycogen.

So over a longer run I am thinking you are depleting both your muscle glycogen stores and your liver glycogen stores. As I said earlier, this situation forces your body to draw glucose from your blood Stream to replenish the diminishing glycogen stores. This in my opinion is why your blood sugar is dropping. It means it can drop during your exercise as well as for several hours after.

Athletes in general have a much more efficient energy system. For instance , I could run a 5 k in less than 18 mins. However, another runner can run a 5 k in 30 minutes. That 30 minute runner’s body is working twice as hard as my body and using a lot more energy than I used. So if you are still gaining fitness, your body is working very hard and using energy ie glycogen at a faster rate.

That is as far as I can go as I am in oral meds not insulin. I hope that helps you to understand why your blood sugars are dropping very quickly during exercise and possibly several hours after.
ed spelling

 

[Melgar]

And here is a useful link on glycogen storage and exercise.

Fundamentals of glycogen metabolism for coaches and athletes - PMC

The ability of athletes to train day after day depends in large part on adequate restoration of muscle glycogen stores, a process that requires the consumption of sufficient dietary carbohydrates and ample time. Providing effective guidance to ...

pmc.ncbi.nlm.nih.gov

 

[jones_48]

Hi, thanks for the replies!

@SimonP78 the time of day is also unpredictable. Because I’m closed loop, my target BG is set to 6.5 and can’t be changed. It then automatically changes my basal rate based on my BS trend, and gives correction doses.
I’ve created a profile which gives 50% of my usual basal and less insulin to carb ratio on run days (but I’m yet to try it).
I’ve just read a book on Type 1 and exercise, and it describes how ‘insulin on board’ is a big factor, and that exercising fasted can be beneficial, have you ever tried this?

@Melgar I’m a 30 minute 5K runner and still gaining fitness, so what you’ve said makes sense but it’s very frustrating that the hypos are so unpredictable.

 

[SimonP78]

I agree that IoB is a big factor and try to avoid exercising with any IoB unless it's going to be short (<1h) and hard (so I'll get hepatic glucose production), or it's first thing in the morning and I need to treat FotF.

I usually ride the hour or so to work fasted (aside a few cups of white coffee, so not completely fasted) to avoid needing to faff with extra insulin for food (aside from the FotF fix) and invariably running high, but it's certainly feels harder than after having had something to eat.

 

[jones_48]

That is interesting. If I cycle to work (12 miles, first half quite hilly) I usually have porridge beforehand but end up going high. Do you eat once you get to work?
What is FotF?

 

[SimonP78]

FotF is "Foot on the Floor" which is a hepatic glucose release as you get up and out of bed.

My ride is a similar distance and also has some lumps and a decent climb both on the way out and back (such is the route to avoid the traffic approaching Bath from the south) - I often just skip breakfast these days (though I am getting milk from lots of cups of coffee!), though I will tend to eat something like a Nature Valley bar (with bolus) mid-morning once the FotF has worn off.

I always found porridge really difficult to deal with - it would always generate a massive spike whether riding or not. If I'm not going to work I'll probably have an apple and some yoghurt, though if I'm doing an all-day ride I'll usually eat a small helping of granola (which is what I used to eat before and after I tried porridge) and accept I may go a bit high initially (I do dose extra for breakfast in this case but not too much) but at least I've got something in my stomach.