So I've been on a pump a long time. I'm trying to smooth out the too-big hills and valleys in my BGs. Am now using CGM sensors to see if that helps. I have figured out how to get at many of the rises and dips in my BG level except for a very confusing dip just before lunch. I've got my BGs steady through the night. I wake up early (5:30 or 6:00 am) and take my largest bolus of Lispro (1 unit per 7 grams carb). I eat my breakfast (cereal; I know, not great. About 80 g!! So I take 11 unit bolus.). My BG still goes up by maybe 60 to 90 over the next 2 to 3 hours. Not sure I can beat that down (some Dawn phenomenon I think). I take no more food or insulin during the morning. Then, inexplicably, around 11 am (that's 5 hours after my bolus!) my BG will suddenly drop by 40 or 50 or even more all within a half hour! My basal rate is constant throughout at .5. I can't understand what could cause the drop. It's as if the insulin is peaking at 5 hours! The insulin behavior at all other times of day is more as expected, peaking in about 1 or 2 hours. Any ideas?
It sounds as though your basal insulin is the source of the problem. Just about everyone requires some "peak and valley" to their basal pattern. In adults, the peak tends to occur in the predawn/early morning hours, and the valley is usually around midday. It is possible that you are simply receiving too much basal insulin late in the morning. Lispro and other rapid acting insulin analogs typically wear off after 4 hours or so, so the only thing that would be making your BG drop late morning would be the basal.
To test this theory, skip breakfast one morning and don't deliver any boluses until lunchtime. See if your blood sugar holds the same pattern of dropping late morning. If it does, the basal is definitely the culprit. It is usually necessary to reduce the basal insulin 1-2 hours prior to the initiation of the blood sugar drop to level things out.
It is a good idea to test, fine-tune and verify your basal settings at each phase of the day. Details about basal testing can be found here: integrateddiabetes.com/basal-testing/
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