Correction bolus lows

Hi all. So it’s not too often that I have to do a correction bolus, but I’m finding that whenever I do one I end up with a low. For instance this morning I woke up to a 215 so I did a correction and when I got to work, about 2 hours later my dex told me I was 86 and falling fast and my meter reading was 67. I guess this means my insulin sensitivity factor is set too low? I’m worried if I increase it then I will get highs after meals. Does anyone else have this issue?

My ISF has needed to be tweaked occasionally. But I don't know that I'd make a change based on one experience. But if you do, I would go ahead and make a small change. Say, if it's currently 1:30, change it to 1:35 and see how that does for awhile. For me I have quite different for different times a day - my daytime one is 1:30 and my night time one 1:60.

Changing your ISF factor should not impact your meal bolus / after meal BG unless you frequently have to include a correction amount with your meal bolus.

In that case, it's possible your IC (carb) ratio was off, but you didn't notice due to the incorrect ISF factor.

When you did your correction bolus for the 215, did you also eat, or did you just correct and then go to work ? If you did not eat, and 'getting' to work involved some degree of activity (even a small amount of walking), then that activity can 'supercharge' the correction bolus. So in that situation, you might want to keep your ISF factor as is, but when it calculates the bolus, reduce it down a bit when you know you will be active after the bolus.

I also think you need to see a pattern, rather than one occurrence, before concluding that your ISF factor needs to be changed. It should be based on doing a correction, not followed by a meal or activity.

I have correction factors for 8a-7p when I am active and a second one for 7p to 8a. It also depends on what you are doing.
How much activity did you have between correcting the 215 and re-checking two hours later?

One idea for the present, cut your bg correction in half and correct again in two hours, make detailed notes, then work with your endo to tweak your ISF.

After doing the correction I commuted to work which involves the train for an hour and then a little walking, but nothing that I would consider strenuous. I also suffer from highs from the time I wake up till I get to work- from 6am to 9am- so my basal rates during those hours are higher. I’m thinking taking the correction and then the basal on top of that could be causing the low. However I thought the correction takes into account insulin on board.

When you take a correction with only basal, then there is no insulin on board.
IOB only comes from bolus.

Another possibility is that your 215 from you meter may have been off by 30-45 pts or so.

Every day there are variations, that can cause the unexpected highs and lows that you experienced, even when all your pump settings are 'right'. I think that's why a CGMS is so helpful ! But if they occur frequently, and you see patterns, then certainly consider some tweaking.