I’ve gotten into the habit of exercising at ridiculous hours of the morning.  5 AM runs, sure!  A long trainer ride – I better get up at 4:30!  I even did a mock triathlon by waking up at 3:30 AM in Texas.  I never used to be a morning person, but I started doing early morning workouts so I had more time for Megan and our two fur kids (Molly and Gus).  We like to spend time together. 🙂


My wife and Molly and Gus (our two fur kids) on a boxing day snowshoeing trip. My inspiration!

However, I quickly learned that my blood sugar behaved differently right after waking up.  I wasn’t dropping low as quickly (without food), everything just seemed to happen more slowly.  If I did the same workout at 5 PM I’d have a totally different blood glucose response.  What gives?

Here’s an example of my experience.  Below is an overlay of BG and HR from a high intensity trainer ride (Sufferfest: There is no Try) done right after waking up.  No food.  No insulin reduction.  My HR is lower in the second half of the intervals because I had to scale it back to 90% – I just haven’t fully adjusted to my new FTP…or I need to HTFU, who knows (insight!  see below).  Anyways!  What this shows is that I started my ride at 4.8 mmol/L and ended close to 5.9 mmol/L.  No lows, no highs.  There were no signs of zone 3-4 causing me to drop, and no sign of the potential highs some diabetics see when operating in anaerobic zones.

Blood sugar in the AM

Blood sugar and exercise in the morning – it can be done, and it’s actually quite easy to manage

So how did I exercise and stay in the “golden zone” (4 to 7, your in diabetes heaven!)?  Well, it turns out that in the morning you still have lots of those dawn phenomenon inducing hormones still present in your body (like cortisol) – they increase insulin resistance.  Furthermore, unless you had a late night correction bolus at like 3 AM, you probably only have basal insulin circulating in your body.  The combo of these two things may work together to help stave off a low.  In my experience, I also find that it helps in keeping my metabolism up for the day ahead and was very successful in reducing my overall total daily dosage of insulin.

Now, researching for this post I did draw a lot from experience – I’ve been exercising at 5 AM or earlier for the better part of a year – non stop, maybe a rest day a week.  I’m pretty much dialled in.   I know what blood sugars I feel comfortable going for a 10k run on , and what duration exercise I need to start fuelling for.  However, this takes time and effort to figure out.  There are some great resources out there for trying to figure this out.  One that I thinks is quite helpful is Ginger Viera’s “Your Diabetes Science Experiment”.  I don’t get any money for promoting it, I just think it’s a good book to help you plan how to sort this stuff out.  However, common sense and the scientific method work well too. 😉

Now, the insight I had while writing this post?  After a bit of reading it may be a lack of glycogen.  While researching for this blog post, I re-read “Your Diabetes Science Experiment”.  In the book, Ginger makes a comment in regards to lifting weights prior to eating, but interval training is anaerobic in nature, so I will quote her here, “if you were to try and lift weights on an empty stomach, you would find yourself feeling burnt out very quickly, because as we talked about earlier, your muscles need to release their stores of glycogen so the glycogen can be converted to glucose and carried back to your muscles with insulin for fuel.”  Since I was doing some HIIT without a spec of food I may have been pushing a wee bit too hard without any fuel.  Lesson learned!

However, your diabetes may vary, and even various authors can’t seem to agree with the theory – even the same author in different years (see 2008 article and 2012 article).  Reading between the lines I suspect there’s a lot missing between the leap from the 2008 to 2012 article – what diabetic therapy is being used, what type of exercise, how long, etc.  So, what do I recommend?  Try it out.  Test often, test before, during, and after exercise.  Learn from your experiences, and keep at it.  You’ll figure it out and your body will thank you! 🙂