Cycling and Glucose

My partner is just getting into cycling and is having a hard time finding a physician that can help her determine the right insulin dosage during the day to help keep my glucose stable during a ride and not tank my HbA1C in the long run. Any tips or know who would be a good resource to help with this?

Info on her routine below:

I take a normal dual wave bolus for lunch and usually do 80% now and 20% squared over 2 hours. that's at about 11:30AM. then, 3 hours before cycling, i suspend my pump entirely. this usually starts around 2:45PM. and my sugars are usually normal-150ish. i don't have a lunch spike but my sugars seems to drop down to about 80 by 5:15PM. even with the basal off. i usually don't drink juice or anything and go cycling. if my sugars pick up during a ride, i restart my basal. if not, i leave it off all through class. then, after class, i test and i'm usually around 200. so i take a bolus equal to about 75% of the basal i missed in the suspend. but within an hour, my sugars are 300.

Cycling can drop my BG like a rock. I divide exercise into a few different catagories: light, moderate and heavy. Light exercise might be a walk while heavy would be super vigourous. Then I also think you need to consider length of time: short, moderate and long.

I like that you are using a temp basal and this is a great tool. Stopping your pump is likely why you are spiking so high, I suggest you just reduce your basal rate. Try reducing your basals about 1-1.5 hours before you plan to start exercise and plan to do the reduction for the length of your exercise. My medtronic pump will let me set a temp basal for 1 hour, for example.

How much to reduce your basal is the tough part. If I am going for a light walk, then I would consider a reduction to 85-95% of normal. If I am biking moderately hard, then I would consider something more like 40-60% of normal.

Another good input is food. I often bike after dinner and will dose for less carbs than I eat. For example, if I eat a 40 carb dinner I may only dose for 20-25 carbs and plan for my exercise to correct the other carbs.

Exercise is very individual and you will have to experiment.

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I don't cycle so I don't have any cycling specific tips but a note on adjusting basal generally:

Adjusting the basal rate down a couple of hours before activity is good because it takes a couple of hours for the basal rate adjustment to kick in. What that means though is that there is going to be some overlap in time, during her workout, where she will have to restart her basal to avoid highs later.

She is giving herself a bolus to cover the impending spike due to loss of basal, which is good, but it just might not be enough, especially if she is prone to post-workout spikes like a lot of us are. is pretty good, and the maths provided are really handy particularly on things like carb burn rates for different exercises depending on body mass and other things.

Cycling wise, there are a couple of things going to occur. First off, you will use a crazy amount of carbs while riding, you will still need insulin to metabolise it, and your liver will do it's best to get involved to confuse matters also.

Before a long ride I tend to stack up on a long burner, usually something like muesli or porridge and use 60% bolus (dif amounts can occur depending on how close to the ride I eat but mostly this is through trial and error). I tend to ride at about 30% basal and have a bottle mixed using a combined carb and hydration drink carrying about 65g carbs per bottle, with me consuming normally a bottle every 60-90mins depending on how my bloods are going and weather.

Hydration is an odd one, as it can knock us a bit off balance which is why I keep banging in the drinks and hydration tabs. The other thing to watch out for is the liver, this can kick in sometimes at the start of a ride with the shock to the system of the activity, or possibly kick in when you up your adrenaline later on when you kick in that sprint of major climb. Getting a jump in BG of 150+ points just off the liver is easily possible, and while something which needs bringing back down, you don't want to correct fully for it so I tend to give a 3rd what would be enough to correct for it to avoid it crashing again. The body will look to recover what it used deployed to raise your BG when the liver kicked in, but it will do that later on which will also need watching out for.

Personally though a lot of this is about learning how your body will react to what you are putting it through on your rides. and that will mean lots of testing while you do your learning about yourself sadly.