I’ve had type 1 for 37 years and have a Tslim and a Dexcom g5. I use fiasp insulin. My blood sugars are in good control but I have noticed an odd blood sugar pattern lately. I eat lunch at noon, usually a chicken sandwich of some sort with 2 slices of multigrain bread, a slice of tomato and some mayo. Plus some water and nothing else. This is about 25-30 carbs for which I bomus 2.5 or 3 units after I finish eating which takes about 20 mins. Everything is fine until 2:30 or 2:45 when my blood sugar shoots up. It can go as high as 280 sometimes. I bolus again when I notice it going above 180 but the bolus takes a longgggg time to start working, often not until 4:30 or so. I checked my basal rate over this time period sevenal times and everything looks great - my blood sugar is a straight line, hovering around 110. Does anyone have ideas about wth is going on? I am out of ideas and very frustrated. Thank you in advance!!
The Fiasp has a shorter duration than the other bolus insulins. It seems to peter out for you after about 2 hours but your digestion keeps on going. I don’t have a CGM nor do I use Fiasp. But if I had that pattern, I would do an extended bolus, taking the 2.5 or 3 units as you do and another 2.5 units over the next 2 hours. Alternatively, you could do your regular bolus and a temporary basal of the additional amount divided over the extra 2 hours.
I like @Willow4’s suggestion of a normal bolus like you’re already doing and then add an extended bolus of 2.5-3.0 units that starts right after your meal bolus and extends for two hours. If you decide on a 3 unit extended bolus I would extend the time to 2.5 hours. Good luck. I’ll be interested to read about your results if you do this.
How do you get a straight line on you can after eating. You don’t see any spikes?
To minimize post prandial (after eating) spikes, bolus ahead of time, avoid high carb foods and limit your portions. Then test for any needed corrections. Exercise after eating, especially a nice low energy walk, is beneficial also. It’s an overwhelming task. Great if one can achieve it; not such a big deal if one doesn’t and the spike is of very limited duration. That is the dance we dance with our nemesis… carbohydrates. 
Thank you willow and Terry, your suggestion worked!
Thank you