Hey y’all! Hope it’s ok if I just rant for a bit.
So I just got home from an extremely difficult tennis game. Whenever I have a match, it’s nearly impossible to keep my blood sugar up because the level of physical exertion makes it drop too quickly. So I’ve been working on ways to combat that.
I walked in the door at 7:45 pm, feeling physically sick from exhaustion and dehydration, only to discover that my blood sugar was at 4-freaking-50. WHAT?? I have no feasible explanation for this, and frankly, I’m rather fed up. It hurts that I can do everything to the best of my ability and have something like this happen. I hate not having control over my own body, and when my numbers go crazy like this, I end up blaming myself, which just makes it worse.
So yeah. Sorry about that, but it feels nice to rant to people who actually get it. 
I appreciate this rant. This is super frustrating. Nothing kills that feeling of “Look, I did a good thing by exercising!” quite like realizing your blood sugar INCREASED because of it. Ugh!!! In case you’re looking for an explanation, I included a link below about why glucose can increase during exercise (I had previously looked it up after a similar experience).
http://www.joslin.org/info/why_do_blood_glucose_levels_sometimes_go_up_after_physical_activity.html
yup.
okay the first huge variable is dehydration, everything is off if you are dehydrated.
understanding how a “normal” works may shed some light, so here goes. your liver is a sugar/insulin sponge. in a normal, you eat anything and your body makes insulin. excess sugar is either burned by activity, absorbed by your liver, or converted to fat. the burning and converting chemical process needs insulin as a catalyst for every cell in your body except your brain. cool right?
so we inject an “analog” it’s not exactly insulin. it hangs out way too long. it doesn’t start as fast because it has to get absorbed through the interstitial before it gets to the blood. long-acting like lantus (or whatever) is a hugely complex chain that blocks absorption so it hangs out for 14-26 hours. your liver may dump and recharge but it isn’t always as accurate as when you can naturally make insulin.
hard physical activity is typically aerobic or anaerobic. the first is jogging the second is weight lifting to generalize. tennis can be both. aerobic tends to lower blood sugar by promoting burning to fuel the exercising muscles, anaerobic can sometimes raise blood sugar because of a complex issue of the activity being mixed with stress hormones the most famous is Adrenalin. adrenalin causes systemic increases in blood sugar because it historically is triggered when you come face to face with a hungry lion in the woods and need a little “boost” so you can evade being eaten.
so my guess from New Jersey is this: dehydration and anaerobic equals a lot of adrenalin equals high blood sugar - or - actual low blood sugar causing your liver to dump all stores. either or both of which could easily cause a huge 4 hundy. sorry you had a bad turn. I hope you feel okay now.
Hi, Joe is right. But I’ve also noticed my post exercise spikes can be very temporary. So I don’t always correct , just wait a bit first. Then test again after testing and drinking water etc. Weight training does that to me. I also play bass in a rock band and the loading , unloading setting up, playing etc gives me temporary high spike also.
Wow @sneathbupp thanks for the advice… you were exactly right! I overcorrected and woke up in the middle of the night with a bg of 38. Next time I’ll try waiting a bit and see if that helps. 
@Joe great explanation, that makes a lot of sense!! It’s great to know that I’m not the only one who deals with this kind of stuff and that there’s a reason for such a crazy number. Thanks so much!
I’ve noticed the same thing after yard work or anything else with a lot of physical activity. I used to correct and be extremely low a couple hours later. I never knew the reason before, but I just stopped correcting after physical activity and it all seemed to work out
Don’t be frustrated it is more common than you think. I belong to an exercise group that is operated by the local health region and the facilitators/instructors are all registered health professionals with backgrounds in things like kinesiology, cardiac rehabilitation exercising, diabetes educators etc. There is a range that T1D blood sugars must be within before you can participate in the exercise class. Here in Canada the range is between 5 mmol/L and 16 mmol/L. (I believe, but don’t quote me, that range is approximately 90 mg/dL to 288 mg/dL). Your 450 mg/dL reading you had after exercise would be approximately 25 mmol/L in Canada and I have experienced the same thing many times over my life. The main issue is eating too much before you exercise (having a BS quite a bit over 288 mg/dL) rather than consuming smaller amounts periodically during the exercise. It may sound hard to do while exercising but actually it is not that hard depending on your exercise activity. Often it requires taking a short break but in things such as a tennis match I’m sure it could be accommodated. Remember if your BS is high before you start exercise it will generally go up during your exercise program. Hope that info helps.
I think I was told to check before exercising and if 250 or greater not to do strenuous activity and if slightly low or in range adjust with 15 g carb increments depending on length of activity. I don’t really exercise anymore, but I remember when I use to swim I would be fine. Several hours later I would drop. My endocrinologist drew a graph showing how even if you don’t take extra insulin, the exercise improves how the insulin is absorbed.
There are insulin independent glucose transporters that are unregulated with exercise. This is one way people used to extend the lives of T1s prior to the 20s.(insulin discovery). Unfortunately, without at least basal insulin high exercise levels will prolong life but the T1 will still die from lack of insulin. But exercise can greatly reduce insulin requirements.
Our son is 14 and plays baseball and basketball. Interestingly, his sugars decrease with baseball (he is a pitcher) but often increase during basketball. I attribute this to the adrenaline rush of a competitive game. Most times the rise isn’t crazy so we don’t change our treatment.
Two hours before exercise, he sets a Temporary basal decrease of 50% on his insulin pump. The duration is usually 8 hours - two hours before game, two hours for duration of game, and 4 hours post exercise. Remember, your body is replenishing all those glycogen stores long after your workout is complete. With strenuous activity like basketball, we want his sugar over 160 to start. His usual pre-exercise numbers are around 100-120 so he typically has a 40g carb snack before practice. Then he checks his BS every hour and takes an additional 20g for every hour of strenuous exercise. After practice or game, he has another 20g snack - remember those glycogen stores!
Everyone is different but we have had some success with this approach. Best of luck!