Delayed hypoglycemic event after exercise

I had my first severe hypoglycemic event since being diagnosed as a type 1 just over a 1.5 years ago. I took my morning Lantus at my regular time at 7:00 AM with a morning BG of 100. Then went to have some coffee and watch the news. Thirty minutes later my Dexcom alarm went off and I was 43! I was surprised so I went to test and after a few steps I almost blacked out.

I ate a few glucose tablets and then drank 2 boxes of apple juice and was still around 60 so I ate a Cliff Bar. I finally started to come back up.

I am completely shocked at how fast it came on. It was so fast I either missed my first Dexcom low alarm (but I don’t think I did) but I certainly did not get much warning. My only guess is that I had 3 back to back days of hard cycling, and that finally caught up with me. However, I am surprised that it hit me almost 18 hours after my last ride, totally unexpected.

I guess going forward I need to lower my Lantus each consecutive day until I have a rest day. I am stating a pump (Omnipod) this coming week so hoping that offers me more flexible basal rates.

This first hypo really scared me :worried:


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I would encourage you to talk to your doctor before making an adjustment to your insulin dose. Also I was curious what was your level when you did your final check last night and how long had it been since you ate? My level starts to drop if the gap between dinner and breakfast is too long.

Hard to balance the need for the highest necessary basal rate at night and the lowest necessary basal rate immediately after waking up if you exercise.
You could try splitting your Lantus into two half shots 12 hours apart. Best solution is probaby to plan for extra carbs first thing in the morning.
Caffeine definitely affects BG and metabolic rate.
Personally, and I think most diabetics, have to deal with the opposite, the dawn phenomenon, which is a rapid blood glucose rise first thing in the morning.

@swilliams1976 my BG was 100 when I went to bed but my Dexcom woke me up at midnight when I was 80, I corrected with a glucose tablet and went back to bed. I do agree that dosing decisions are best done with my Dr but she is booked out for months. She is a diabetic herself and I think she see’s every #T1D in area. So, I usually just make small adjustments and see that happens. I do think I went too long between dinner and breakfast with some depleted muscles.

@SpecialEDy Yeah, it sure seems that when my basal dose works well for cycling it’s too little for the morning. Certainly a no win situation. We’ll see if going on a pump gives me more knobs to turn and finner adjustments. I would sure hate to give up cycling, after 30 years, but at this point it’s more trouble than it’s worth.


If you are 100% dependent on a doctor for insulin adjustments, you are in big trouble anyway.

Sorry about the low, they tend to suck.

No need to worry or adjust anything lantus because you are pumping now

Yes exercise and yes mornings are both difficult sometimes.

It’s very possible that you depleted your glycogen stores and when that happens you can get a tough low but you did all the right stuff so in that respect nice job!

As soon as you get a programmed basal dialed in you can the start t adjust it… yourself… for exercise. I reduce mine by 70% for cycling.

Good luck!

I am in the process of trying to lose weight so the trips to the gym have caused a few lows. Try to find the balance before you give up on cycling. Exercise is good for us even if I feel like it’s a version of torture lol

An insulin pump would be excellent for exercise. You arent locked into your basal rate for 24 hours like with Lantus, and you can lower your basal for only the few hours of high activity.

Jeff @everlook, I really hate to contradict you, but in my opinion, and in the opinion of several outstanding endocrinologists with whom I have dealt, it is not appropriate to wait for a doctor to make dosing adjustments. making intelligent dosing adjustments is one of the first requirements for effective diabetes management. Each of us is living with, and observing, our own diabetes every hour of every day and we are in a better position to understand the interaction of food, activity and insulin.
The important key to adjustments is "small increments / decrements and then close observation.

@Dennis Contradictions and advice are always welcome, Thanks for your input, much appreciated.

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I used to do a lot of biking and had similar issues. Your muscles use quite a bit of glucose as they recover. The only suggestion I have is to eat when you take any type of insulin.

I’m glad you’re okay, that sounds like a really terrifying feeling.

As others have mentioned, hard workouts will deplete your glycogen stores, which your body was obviously trying to recoup.

Another aspect of T1D that wasn’t well explained to me (by our endocrinologist OR in nursing school) is that it’s not a low glucose, but the presence of insulin (in this case your Lantus) that prevents the pancreatic alpha cells from releasing glucagon, so your body won’t necessarily respond appropriately to hypoglycemia. In non-diabetic people, the liver churns out sugar in response to glucagon. Perhaps speaking with your endocrinologist about using “micro-dose” glucagon injections to prevent these events could help.

While it’s often difficult to get appointments in a timely manner, often getting a response to an email or phone call with a quick question or two is feasible.

Best wishes for an event-free cycling summer.

I agree that trying to figure out your body’s response to exercise is very tricky. I can get up and run first thing - 13 miles, no food, and still have a normal BS 15 minutes after I am done. Then later in the day, or even the next day, I go super low. It seems hard to predict, and of course I exercise differently each day, and some days not at all. I don’t have a pump, and use a Libre. Most of the time the Libre is great, but not so great for exercising, and of course, like any GCM, not so great when a drop is quick. Anyone with running experience and advice - I welcome it!


I have had a incidents with Lantus and/or exercise lows. I have had times where I got a severe fast drop after taking my nighttime dose. Exercise was not even part of the equation. Endo had no answers. Reading indicated I possibly hit a blood vessel. Happened approx once a year. Yes, very scary!
Lantau was just not for me for multiple reasons.

I’m on Omnipod now and love it. The ability to change my Basel at will is wonderful as my background needs change constantly. Patterns fade as fast as they arrive. I am also very sensitive to exercise or long term movement.

I agree with others with regards to making dosing decisions / changes. This is your disease that you live with so educate yourself because i have learned that I often know more about my personal management than my endo. Everyone’s needs are different.

Your experience with the delayed onset hypoglycemia sounds familiar. If I do moderate long term or high intense exercise I can have a very sharp low up to 48 hours after with then a lower Basel need to follow. Depends on how long I’ve used the muscles for. Now I know to look for it. My insulin needs will stay stable then bam! I’m hit. Chugging sugar :stuck_out_tongue_winking_eye:

I also read that T1D’s have impaired hypo recovery with regards to glucagon dump. I would say this is correct for me per real life experience however my very low carb diet may play a role.

Don’t give up. My best advice is the ensure proper nutrition post workout, be prepared for the low (muscle recovery), look for patterns and think about lowering Basel as needed especially to avoid overnight lows.

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@AverageGirl Laurie, yeah, looking back I really think the sudden low was caused by the Lantus injection and not from exercise. I did hit a blood vessel that day and the injection stung more than normal. I am 3 weeks in with the Omnipod and doing pretty good.

Thanks for your comment.