When do you take a correction bolus?

I checked my blood sugar 2 hours after lunch and it spiked big time! I was 82 before lunch and I'm 205 now. Since I took a 4 unit dose of humalog 2 hours ago, I have a little over 2 units of insulin left in my system. With a sensitivity factor of 65, I need about a unit of insulin to bring down the high, but I've already got 2 units in my system.

So here's the question, in situations like this one (I've recently eat and still have some meal bolus on board), should I still correct? Or do I just wait? I don't want to go low and then have to deal with a rebound high later.

No, if I still have enough insulin on board to cover the correction according to my ISF, I don't correct, because that would be stacking. I would wait and see if the insulin corrects the high in a couple hours.

That being said, a couple comments: You are only correcting down to 140 I see. Even though "under 140" is, in fact, my target two hours post prandial, I do correct to 110 when I figure corrections which is a lot more comfortable number. But in the case you describe you still would have enough insulin on board (and can only correct in whole units - it's a lot easier for me on a pump because I can correct tiny fractions if needed).

I see you are very recently diagnosed so just a couple other things to look at are being sure your ISF is correct by trial and error. It also can vary by time of day. Mine fore instance is similar to yours at night (1:62) but only 1:42 during the day. Also to make sure your I:C is correct and to minimize carb intake especially in the morning. For instance my I:C at breakfast is only 1:5 (1:10 and 1:18 for the other two meals). So I try not to eat too many carbs (around 20) as I don't like being in the position you describe of being 205 and not being safe to correct. What was the lunch that spiked you so high? Maybe that is a meal that just doesn't work for you and it would be easier to change it or change the portion so you don't go that high.

Lastly, I use apidra which for me only lasts 3 hours so that makes it easier to keep track of and to correct.

I do think I need to work on my SF and I:C ratios. I'm going on a pump on Tuesday and I'm planning on tweaking those numbers with the CDE then. I'm not quite confident enough to work on them without guidance yet. Right now, since I'm doing injections I can't take very precise insulin doses; I'm looking forward to the precision of a pump.

I agree with you. I don't like at all being this high and not being able to anything about it. I eat roughly the same meals every day (I'm a creature of habit and managing my D a little easier), so I'm confused as to why I'm so high. I didn't eat anything unusual and I've never had a postprandial spike this high after lunch.

As time goes by you'll learn what us very logical people learn only reluctantly: Sometimes you can figure out why a number happened and sometimes it's inexplicable (or the D gremlins as we like to say)You might also be coming out of your honeymoon so things are changing and yes, all your numbers will need tweaking. It's great you're going on a pump! Especially when you're insulin sensitive it's so much easier to cover things more exactly!

Congrats on your pump but do know that it's a learning curve, so don't get impatient if your numbers are worse not better for awhile. It takes time. But this is a great place to ask questions as lots of people are in the same boat and have experience to share. Also if you haven't already bought the book Pumping Insulin by John Walsh (who wrote Using Insulin - also a bible) do get it. I'm not so invested in the "formulas" because imho we are all different but there's an incredible amount of useful information.

This process is not an exact science. I do not usually correct until my original bolus is out of my system, and here is why - I have had numerous times when even though I bolused 2 hours ago it just hadn’t kicked in yet for whatever reason. Maybe delayed absorption? I don’t know. But it has resulted in me over correcting and going low. It is so weird. It had been two hours and I’m thinking “shouldn’t I be dropping and/or be in normal range by now” and then I correction bolused and dropped quickly before the correction would have had time to work… And then go low.

I will correct at two hours if I am much higher than expected. When I first went on my pump I totally miscounted a meal and at 2 hours tested at slightly over 250. My pump told me to test for keytones and suggested a correction of .05 because I still had a lot of insulin on board. Needless to say I developed a much more sceptical attitude towards IOB calculations and bolus wizards at that moment. I ended up correcting down to 150 and drfited slightly low about four hours later. I had a small snack and was fine.

I will also correct at two hours after breakfast. I eat the same meal everyday and know where I need to be at 2 hours post to end up ok at 4 hours.