I was looking at my book of numbers and seeing a pattern of lows between dinner and bedtime. I was about to tweak my basal numbers when I looked closer and realized that all the lows were after I'd done a correction either with my dinner bolus or at my dinner post prandial. Then it dawned on me that I used the same ISF all day, and never even thought about it. But it made a lot of sense that would vary since my I:C ratio is 1:5 at breakfast and 1:21 for dinner. I didn't even know if my pump had settings for different ISF's.
Of course it does! Duh! So I set my evening ISF to 50 (my daytime one is 40). I think I might tweak it even a bit further apart. So does everyone use the same ISF all day or do you have more than one? How far apart are they? I can't believe I just noticed this!
My ISF is 20 points lower at night than during the day. A lot of that difference is to avoid lows at night. I also think that during the day I have food still coming into play even if it’s been many hours since my last meal or snack. Therefore my corrections need to be more aggressive. I’m very insulin sensitive, so my correction factor is 70 during the day and 90 at night.
I’m not sure that my ISF numbers are very scientific, and I’ve never tried to have more than two. My overnight rate is actually pretty accurate because I’m almost always in a good range in the morning after correcting during the night. I override my pump fairly often on corrections during the daytime because of food already eaten, food I want to eat, planned exercise, etc.
When I looked through the insulin models of "Using Insulin" and others, I concluded that the carb sensitivity or Carb Factor (CF) (how much 1 g of carbs raises your blood sugar) is basically constant, but your ICR and ISF would vary based on how insulin sensitive you were (and other factors). And in general, your ISF = I:C x CF. So if your breakfast I:C is one quarter your dinner I:C, then it is reasonable to expect that your breakfast ISF would be one quarter as well (i.e. 50/4 = 12.5).
The calculations are a guideline, and confirm your hypothesis. But it is better to establish correct ratios with testing.. If I correct in the morning, I take lots more insulin. In the morning, part of my problem may well be higher insulin sensitivity, but I also have to fight Darn Phenomenon.
My pump has a different setting for each meal time My I:C, and correction drop all day.
You can also set a higher target range for post prandial BG times and this will soften up your correction insulin. You can also stretch out your duration to soften corrections but
