High Blood Glucose During A Run: How To Handle The Carbs?

Today I went for a long and intense run, the first big one in preparation for my next marathon.

Everything was amazing: strong legs all throughout the session, the weather finally getting warmer (it’s early February, but I am sweating instead of freezing, and I love it), and a good pace too. There was only one item on the list that I could not tick. And that was my blood glucose during the run! I woke up with a blood glucose of 150, and came back with 266. That sounds almost impossible: aerobic exercise should lower your blood sugar after all, isn’t it?

Well, yes. But it is a bit more complex than this.

After some very intense thinking and a big bowl of fruit, I am ready to sit down to untangle and share the “mystery” of what happened, dissecting what I did wrong and how I handled the situation. Life isn’t perfect and we can’t be in range 100% of the time after all. Let me dive into the wonderful sequence of wrong and corrective decisions that made this run a rather bumpy one!

First Mistake: Ignoring The “Dawn Phenomenon”

I almost always run in the early morning, fasted. I prefer that because I don’t have to deal with the uncertainty of insulin on board and food in the stomach. Eating and injecting before a big workout can add some unneeded complexity that could easily take a type 1 diabetic to hypoglycaemia, if not handled with care. I almost never have issues with my blood glucose because the so called “dawn phenomenon” keeps it up.

The “dawn phenomenon” is a natural elevation of blood sugar levels that occurs when we wake up: our body perceives that the day is starting, and some glucose is released into the system to give a good kick of energy.

As mentioned, I woke up to a CGM reading of 150, which was perfect given the bout of exercise I was just about to get in. But then I saw it fluctuate toward 140, 135, 130.
And I did what I naturally do in this situation: I eat something to bring my blood glucose up and have a safety margin from hypoglycaemias during the run. In particular, I ate two big medjool dates, which amounted to around 40 grams of carbohydrates. Excellent choice, because they gave me a big kick of energy before the start of the run and raised my blood glucose to 170 - right where I want it to be when I start running.

But then I forgot that the dawn phenomenon was about to do its thing, as it does every morning without fail, and that it would probably stack on top of the glucose elevation generated by the dates I just ate. This was the first mistake: ignoring a basic fact of biology that I know occurs every morning without fail, because I see it on my CGM. This morning would not be different, and I ate on top of it. What did I expect to happen?

I don’t know, but then I did another mistake that certainly did not help.

Second Mistake: Forgetting My Pre-Workout Bolus

Yes, you read it right. I totally forgot to take my bolus. I normally do not inject a single thing before running, but when I eat something I know I have to account for it somehow.
When I have to take some units, I usually calculate the amount of insulin I would normally need for that amount of carbohydrates - given my carb to insulin ratio - and just take half of that amount, or one third depending on the day and the situation. So if I usually need, say, 4 units for 40 grams of carbs, this time I’ll take 2 or less.

I did the calculation, weighted my carbs, and planned for my insulin injection. Fantastic! Except that I completely forgot to inject.

These things can happen, and that’s ok. I realized it only half way through the run, when I became aware of the fact that despite the sustained intensity of the aerobic effort, my blood glucose was probably rising to a level that I was scared to see. And that is the point where you need to make some bold decisions.

What to do now?
Should I prioritize the athlete in me and keep the carbs coming to make the workout a success, or should I take care of the diabetic in me by avoiding any additional carbs and let my blood glucose come down, possibly causing a drop in energy?

And that leads to the first decision.

First Decision: Athlete First or Diabetic First?

When a run goes on for more than 60 minutes, I’ll always eat something (around 30 grams of carbs every 45 minutes or every hour). On this day, I knew I would be on my legs for two hours, and the quality of the workout was the only thing that mattered.

After one hour I confronted the athlete-vs-diabetic dilemma, but it was actually an easy call for me. It was a long run, a crucial step in the training block, and I wanted it to be high quality. So I forgot about the diabetic Giovanni with a likely high blood glucose and fed the athlete Giovanni with what the athlete Giovanni needed to keep running strong: carbohydrates.

I took my running gel perfectly aware of the fact that my blood glucose was already higher than I wanted it to be and that this would elevate it even more. And I was totally fine with it. When I am in range 80-90% of the time during the week, I can sacrifice a few hours and be out of range for a specific purpose. I will also always prefer being on the higher side than having to interrupt a run for an hypoglycaemia, a much, much dangerous situation.

And I was happy with the outcome of the decision. My running performance stayed at its best until the very last step. I finished my workout feeling good and with a blood glucose that was high but not overly dramatic: 266.

I would now go home and have to feed a body that was screaming for nutrition after such a stressful couple of hours. Time for another decision.

Second Decision: What To Do With My Post-Workout Meal?

As every endurance athlete knows, recovery is absolutely crucial to avoid injuries and keep the body in good shape during a training block. Marathon training can be hard on the body, and it is our duty to feed it and rest it properly. Good sleep and good nutrition are two pillars of an effective recovery.

Knowing this, I step into my apartment with a high blood glucose (266, remember), a body with depleted glycogen stores and screaming for nutritious food. The disciplined diabetic in me would normally calculate the bolus dosage, inject it and wait the appropriate time before eating to let the blood glucose come down and avoid other spikes - up to one hour, in this case.

But the athlete in me wants to allow the body to bounce back from the immense stress of such a big training session, knowing that missing a nutritious post-workout meal would increase my future risk of injury. So what to do? Eat and risk a higher blood glucose, or postpone my meal and make me more injury prone?

Post-workout fruit bowl: 3 apples, 1 banana, arugula and other leafy greens, chia seeds, lemon juice, turmeric, pepper and cinnamon. I also ate some walnuts, around 300ml of soy milk and 20 grams of 100% dark chocolate. Around 150 grams of total carbohydrates and 20 grams of total fats. Eaten slowly and regardless of my blood glucose. Recovery was more important here.

Once again, the decision was made easier by three main reasons.
First, the big run made me immensely more insulin sensitive, so I was confident that my body could absorb carbohydrates much more efficiently.
Second, the type of carbs I eat are whole and plant based, and since these foods promote insulin sensitivity they are incredibly easier on the blood glucose. In other terms, I eat fruits and greens, not bread or any other such food.
Third, I am diabetic 95% of the time, but when I run I am an athlete, and I do what is needed to take care of the athlete for that 5% of the time.

In practical terms, there’s a 30 mins to 1 hour feeding window to consider for the body after an intense workout. I calculated the normal bolus amount I’d need for breakfast, took 70% of that (because I knew the run would compensate for the other 30%), waited 30 minutes and then ate. I started my breakfast with a blood glucose of 230 - not optimal -, but I ate slowly and trusted the process. Whole, plant based, carbohydrates rich foods (fruits and leafy greens) plus a long run plus careful bolus calculation plus slow eating would not spike my glucose again. And so it happened! My breakfast fruit bowl contained 160 grams of carbs, but by the time I finished eating I was at 150. And two hours later at 145, knowing that it would come down further.

Lunch: 800 grams of potatoes (yes, I love to eat plain potatoes without any dressing or spice), black kale, mixed salad with beetroot, carrots and 150 grams of black beans. Apple and orange for dessert. Around 230 grams of total carbohydrates. Around 5 grams of fats. Eaten slowly, in 30 minutes, to avoid spikes.

Conclusion

It is not easy. But having a solid process to take care of the diabetic provides some mental relief when dealing with the athlete. I’ll happily trade in some time in range for a couple of hours a week with higher blood glucose, if that means I can run energetically, recover well and keep my long term health on track. Two hours with a blood glucose of 260 are nothing when the rest of the week is properly handled, and the blood glucose is in range 80-90% of the time.

*An occasional spike in an overall stable blood glucose management. Target range (the grey area) set between 80 and 150.*

Most importantly, when things go wrong it is essential to take the time to think and figure out the whats and the whys. That’s it, in a nutshell! Feed the athlete first, then deal with the diabetic. It was not an optimal training day from the diabetic’s perspective, but the athlete was happy. But the diabetic is happy 99% of the time anyway, so the trade-off is a no brainer.

Let me know if this post helped, and please do not hesitate to share any thoughts or experiences you faced! I love to learn from others and am always keen to make my blog a small platform for the community of type-1 diabetics to share and learn from each others.

See you next week!