Blood Sugar Trends
Although I don’t wear a continuous glucose monitor, I learned a very important concept from the experience of wearing a CGMS a few years back: blood sugar trends. Simply put, the number on my glucose monitor does not exist in a vacuum, but rather has to be understood within the context of where my blood sugar has been and where it’s likely going.
So, a blood glucose level of 140 mg/dl before exercising could be fine. But, if my blood sugar had been 250 mg/dl an hour before that and I’d bloused 1-2 units of insulin to correct it, then I’d probably need a snack before exercising to keep my blood sugar from bottoming out; so logical.
Why then, do I have a hard time remembering this simple concept in my daily routine? I am fairly good at considering the overall context of my blood sugars when it involves exercise (so the example below rings true for me). However, on a fairly regular basis I forget about previous correction boluses of insulin when I’m delivering a meal injection, which often leads to lows immediately after meals.
For pump users, this is easily addressed by handy “insulin-on-board” calculators that warn you about this very issue. I suppose for those of us on MDI, the best bet would be to log my numbers and insulin doses… ah, logging!
How this often plays out for me is at dinnertime. I tend to run a bit higher in the late afternoon. My blood sugars are usually good after lunch so maybe it has to do with the timing of my Lantus injections (I do one at breakfast and the other at bedtime). But, whatever the reason, I see more blood sugars in the 200 mg/dl range around 4:00 p.m. than I’d like. I typically correct conservatively for these and end up in a good range at dinnertime. With meals that generally have little carbohydrate at dinner, I still bolus about 1 unit at dinner (based on my blood sugar at the time).
Here’s how this plays out: I’m getting the kids ready for bed and doing all of the nightly chores around the house, I suddenly feel low, test to confirm it, and then think “Oh yeah, that correction bolus from earlier! I didn’t need that much more insulin for dinner!” That’s the trick; I need to think of my dinner bolus as more or additional insulin to what I already had on board from the afternoon.
My blood sugar, while in range or “good” at dinnertime, actually reflects a blood sugar downward trend. My blood sugar is dropping. Therefore, dinner probably doesn’t require a bolus (given the carbohydrate content is low). In fact, I could think of my dinner as “treating” the dropping blood sugar from going low.