Just Another Diabetic Cyclist

sm-06051Type 1 diabetes sucks. Cycling, however, doesn’t suck. So how do we put the two together? With hard work, diligence, knowledge and a sprinkling of modern technology. At least – that is my approach.

First off – a disclaimer. I’m not a doctor. Please read my Standard Medical Legal Mumbo Jumbo. Did you read it? I’ll wait…

Training for cycling events at even the moderately-serious recreational level takes a lot of fine-tuning. In a sport where a few watts can make a huge difference, things like diet, sleep patterns, and training scheduling can separate the mediocre from the truly awesome. Throw in a metabolic disorder like diabetes and it can feel like 10 times the number of variables to try and manage.

Team Novo Nordisk Pro CyclingBut before we get all doom and gloom don’t forget that there are Type 1 diabetics performing at the highest level of almost all sports. And cycling has an entire world class team full of diabetic riders. So no, diabetes is not an excuse not to excel at cycling if you want to.

But… it doesn’t hurt to have some tools. If you are a diabetic, you’re undoubtedly already aware of these devices.


CGM stands for Continuous Glucose Monitor. It is a device that does what finger-stick blood tests do, but constantly and throughout the day. However, they do it in a slightly different fashion. They (generally) do not measure your blood glucose levels directly, but rather infer it by taking measurements in the interstitial fluids – the fluid that surrounds the cells of our body. These all involve some sort of device that is inserted under the skin that takes the measurements. They then transmit this data – usually wirelessly – to some external receiver.

Since they are not measuring blood glucose (BG) levels directly, there are some trade offs. First, these devices generally lag behind about 15 minutes or so from actual blood glucose (BG) changes. What does that mean? Well, if my BG was actually 85 mg/Dl 15 minutes ago, and has now plummeted to 50, my CGM may incorrectly tell me that it is currently a safe 85.

To help alleviate this, many CGM manufactures are now employing software algorithms to predict BG trends in advance and thus mask this lag.

In addition – a CGM is not a replacement for sticking your finger for traditional BG measurements. Again, since the CGM is not measuring directly some calibration of the numbers are needed. This means that most CGMs have a small amount of “learning” that the devices need to do to correlate the data from the sensor with actual, real BG levels. Part of this learning involves traditional finger sticks, and feeding that “real” number into the CGM so it can help fine-tune the algorithmic calculations.

However, with this data streaming in near real time, CGMs can alert you when BG levels are dangerously high or low. And – perhaps more importantly – they can even alert you when they are within range but are changing rapidly. This can be invaluable when you are on the bike and training hard – giving you enough time to get some carbs into, and absorbed by, your body before being impacted from an energy sapping hypoglycemic event.

Personally, I can not imagine riding the way I do without a CGM. This is especially true for folks like me that have an insensitivity to the symptoms of hypoglycemia. Even if I do feel the symptoms, they very much resemble the same sensations I can naturally induce with a really hard, pushing the boundaries type effort. This can make it extremely easy for a diabetic cyclists to completely ignore a hypoglycemic event until it is so severe they become incapacitated.

Impromptu survey:
Do you use a CGM?
If so, which one?
Scale of 1 to 5, 1 being hate it and 5 being wouldn’t ever change brands, what do you think of your CGM?

I recently did a bit of an impromptu survey on a Type 1 Diabetic Athletes group I belong to on Facebook. The overwhelming response (like 20 to 1 in this very unscientific poll) was that these folks had a CGM and loved it. In addition, almost as high of a percentage of the respondents reported using a Dexcom CGM in specific. This is, incidentally, the same CGM that I use.

Insulin Pump

Type 1 diabetics – in contrast to the very different yet similarly named Type 2 diabetics – have to inject insulin. Period. No insulin, no life. As in going to long without insulin will literally result in your death. There is no amount of diet control, exercise, or lifestyle choices that will change that.

Type 1 diabetes – so goes the current scientific research – is an autoimmune disorder. It is the result of the diabetic’s immune system attacking and killing off the cells in the body that would normally produce the hormone insulin. That is why Type 1’s need to inject insulin – there simply isn’t any other source.

However, how those injections are physically carried out is another matter. Traditionally, this has been via syringes. This is sometimes referred to as MDI in the diabetes community – Multiple Daily Injections.

But this is where things get a bit tricky. There are actually two different functions performed by insulin.


Bolus insulin is the insulin that is delivered in direct response to eating. This is actually what most people will probably think of – if they think anything at all about diabetes. If I eat anything with carbohydrates, I then take an amount of bolus insulin in direct response to those consumed carbs. I want this insulin to be very fast acting – it needs to be in my blood stream to counteract the glucose that my digestive tract is going to start dumping into my bloodstream. Count carbs… take insulin… eat. Count carbs… take insulin… eat. This is a huge part of the diabetic’s day. How much insulin to take (the insulin/carb ratio in treatment terminology) can actually be very much impacted by your exercise levels. You see, exercise makes it easier for glucose to get into your cells – meaning less insulin for the same effect.

But let’s take a step back and address what we haven’t yet. What the heck does insulin actually do?

There are 101 really great explanations about insulin out there on the web. But the huge oversimplification: insulin allows your cells to use glucose as fuel. Glucose is the gasoline for the engine of your cells. And insulin is like the release for the fuel door on your car that allows more gas to get into the tank and fuel the engine. No insulin, and it is as if the fuel door is locked despite you standing there with a gas pump in your hand. Eventually, the engine will run out of fuel and stop running. (Please people. This is just an illustrative analogy. Don’t sit at the gas pump with your car running…)

So, continuing our crude “fueling up the car” analogy – exercise makes the nozzle you use to fill the fuel up flow a little easier. You can think if it a slightly different way and say that exercise makes your body use insulin more efficiently. Because of this, the diabetic cyclist has to be aware of this change and modify their bolus levels when they are out training. Oh…. and don’t forget, that exercise potentially impacts the interaction between carbs and insulin well into the next day. This is, unfortunately, one of those things that you will need to work with your doctor to figure out what is right for you. Human bodies are extremely varied, and diabetes management unfortunately requires a fair amount of trial and error to get right.

But adjusting bolus rates isn’t the hardest part of this this. Remember when I said there were two different functions performed by insulin?

Basal Insulin

Basal insulin is probably the trickiest part for any diabetic athlete. Our bodies naturally introduce a slow, steady trickle of glucose into our blood stream. This is the fuel for our bodies “baseline”… one of the most important of which is brain function. Because of this, our bodies need a slow, steady trickle of insulin to match it. This is basal insulin.

Traditionally, this was accomplished by manufacturing a completely different type of insulin to be injected separately from bolus insulin. The basal insulin was engineered to release slowly, over time. This allowed Type 1 diabetics engaged in insulin therapy to take one, maybe 2 injections per day to account for this basal function – instead of a new injection ever 30 to 60 minutes.

However – remember what I said above about exercise changing how much insulin is needed for a given level of glucose? That same thing applies to basal insulin. And if I’m filling my body up with the proper amount of basal insulin for a day I’m sitting on the couch, but instead go out for a hard physical effort… bad things can happen. Or, conversely, if I go for bike rides every day, but take a day or two off for some reason, I may find that my basal rate is way to low for my lower activity level. Result: high blood glucose levels.

But, technology to the rescue. Insulin pumps, unlike multiple daily injections of combinations of bolus and basal, provide much more flexibility. That is because they can actually utilize the same fast-acting insulin used for bolus injections, but also slowly trickle it in to address the basal needs. This simply would not be practical with multiple daily injections. And that can be a game changer.

If I am simply trickling in insulin in near real time for my basal treatment, and I decide to go out for a bike ride, I have a new option. I can dial down my basal rate temporarily while I’m exercising. I’m not “committed” to that big, slow-release basal insulin taken via injection. I can adjust things – on the fly!

And this is something I often do. If I know I am going out on a good ride I will use my insulin pump to reduce my basal rate. For me (again, through trial and error) I’ve found that reducing my basal rate to 50%, starting an hour before my ride and continuing an hour after it, works really well. Why an hour before? Keep in mind that these are human bodies, and insulin released into the blood stream isn’t immediately delivered to the cells that need it. Furthermore, insulin injections are also not delivered directly to the blood stream, but rather are injected into the fatty or muscle tissue to be slowly absorbed into the blood stream. This delay provides a valuable buffer that can “smooth out” the insulin reaction. But it also means that us T1Ds need to be patient at times. We need to think about how much insulin is already floating around in our bodies before we go cramming more in.

Frankly, this basal rate adjustment is quite possibly the most important tool I have in managing my diabetes on the bike. I’ve often wondered, if I was forced to give up one of either my pump or my CGM, which would it be? I don’t honestly know…. but I feel like in the overall scheme of things as a cyclist the pump is more important.


I wouldn’t be surprised if any non-diabetics that have read through all this (which would be fantastic if they did, by the way) are thinking “Great! CGM. Insulin Pump. You’re set!”

Yea. I wish.

Truth is, all the trial and error leading to carefully planned regimen in the world will fail some days. Human bodies are complex beyond our ability or current knowledge to predict. Just like a 70% chance of rain tomorrow may end up with bright blue clear skies all day, that 50% basal rate adjustment before a ride might go horribly wrong one way or another.

There is however one specific issue I’d like to bring to the attention of diabetic cyclists out there. It is something that it took me years – and finally a helpful diabetes educator – to understand.

Our bodies have evolved to conserve fuel as much as possible. And glucose is that fuel. But our bodies also know when it is important to pour the fuel on for that big effort. And that big effort in this case is going anaerobic.

The liver sits on some huge stores of energy, and is willing to release them into the bloodstream if the muscles need them. Grinding up a hill, sprinting to the city limits sign, turning into a gnarly head wind… these are all things that can result in your muscles screaming for glucose.

Now remember above… all those carefully calculated reductions in basal insulin rates that resulted in a lower quantity of insulin in the blood stream during exercise? What happens if our body decides to release a flood of glucose to meet the demands of our muscles.

That’s right – high blood sugar. While exercise usually results in lowered BG levels compared to the non-exericising baseline, there is a tipping point where the exact opposite can happen.

I’m not going to go into more details on this. It is something to discuss with your healthcare professionals. But I really do wish someone had made me at least aware that this was something that could happen much much earlier on in my life. I spent countless time thinking that I had simply adjusted my basal/bolus rates incorrectly before I understood this concept. Since then things have definitely improved for me.

But there is on inescapable fact. Until they give us an artificial pancreas or other treatment option, Type 1 diabetes will be a hard, challenging, time consuming demon to live with. And while it is true that it is not an obstacle that can not be overcome, it is still a colossal pain in the ass.

Which brings me to my final point. Like diabetes management, diabetes research is hard, and expensive. And the companies that make our pumps, our CGMs, and the insulin are, unfortunately, not motivated to find real cures that would ultimately undercut what is a very lucrative business for them. One can easily spend the equivalent of a good commuter bike a year on diabetes management with really good insurance. And the price of a stable of Pinarellos if you don’t have good insurance (…or Colnagos, or Cannondales, or whatever the cool kids are riding these days.) As such, funding for diabetes cure research has to come from other places.

Those are places like the American Diabetes Association, that have a long history with cycling. They put on events like the Tour de Cure. In fact, Tour de Cure was the first public cycling event I ever took part in. I highly encourage you to find a local Tour de Cure ride and take part. I’m doing two of them myself this year. Or, if you prefer, find a rider and sponsor their efforts (like me, or maybe even… me.) Every little bit helps. While you may be throwing a donation to Just Another Cyclist, you may ultimately help save a life.