Little Changes, Big Difference - Part 1: Blood Sugar Trends
Read Kelsey's intro to the 5 part Little Changes, Big Difference series
As I attempt to bolus more accurately, I've found the one of the most important questions to ask myself "pre-bolus" is: "What is my blood sugar doing?"
Note that the question isn't "What's my blood sugar?" because that answer only provides part of the picture. A single snapshot number, such as 96 mg/dl or 157 mg/dl just tells me what my blood glucose value is for that one test. (It's troubling to realize that if you test your blood sugar twice in a row, you'll often get different results. The accuracy of our glucose monitors is a whole other can of worms that we can open at a later time!) Basing your bolus decision on your current blood glucose reading alone is not going to yield a positive outcome all of the time.
That's because, our blood sugar is always doing one of three things: rising, falling, or holding steady. If my blood sugar is 110 mg/dl at noon and I'm about to eat my lunch containing 30 grams of carbohydrate, I should bolus differently based on whether that 110 mg/dl reading represents a rising, falling, or steady blood glucose trend.
Here are three scenarios to illustrate the idea:
- Today, my breakfast was unusually high in carbohydrates. Before I rushed out the door at 8:30 a.m., I ate a bowl of cereal and bolused for it. An hour or so later, my blood sugar was 250 mg/dl. Frustrated, I delivered an aggressive correction bolus, which left me quite low afterwards. I suspended my basal rate and treated the low with some cookies that were in my office. Thus, by noon, my blood sugar was 110 mg/dl and rising. When bolusing for my lunch, I should factor in a correction for the snacking I did earlier to treat the low.
- This morning, I had some eggs for breakfast at home and then my typical banana and peanut butter with coffee at my desk around 9:00 a.m. I must have miscalculated whether my banana was "medium" or "large" because I didn't bolus enough and my blood sugar was 195 mg/dl around 11:15 a.m. I gave myself a correction bolus and then got busy at work. When I tested about an hour later, my blood sugar was 110 mg/dl and falling. Since my blood sugar is trending downwards, I do not have to bolus early for my lunch. I could set a combination (or dual wave) bolus to deliver insulin over the next hour so that I won't go too low before my lunch glucose get into my blood.
- I woke up with a blood sugar of 90 mg/dl and proceeded to have a high protein breakfast of scrambled eggs and turkey bacon which required very little insulin. My morning was so busy that I just snacked on an ounce of almonds before testing my blood sugar at noon. 110 mg/dl represents a steady blood sugar level. Since my blood sugar is holding steady, I can deliver a typical lunchtime bolus and wait 10-15 minutes before eating if I'm consuming something containing fast acting carbohydrates.
The timing of insulin delivery and carbohydrate consumption is critical to stable blood sugar control. A big key to getting the timing right is being aware of what direction your blood sugar is trending when you get that snapshot with your glucose monitor. The more often you test the more accurately you can gauge what your blood sugar is doing. Basically, you can mimic (to an extent) the kind of information that a continuous glucose monitor provides by testing often and looking at your blood sugar trends throughout the day.