When you get to the point when you are more proficient and ratios all worked out, the other thing to consider is what activity levels are also planned during that time. You may need less if you were planning say a walk than you would if you were planning on staying at home watching tv etc.
So true. It really surprised me to find out that activity was making a huge difference in my bolus dosing and that the actual activity can be deceptively little. I'm past the age of sprinting for a bus or my former 10 mile runs. But a short walk to the local shop, a little bit of gardening, some DIY repair, hoovering (yes, sometimes) - all these modestly active things can and do make a difference.
The trickier part is deciding by how much to reduce a bolus in anticipation of future activity. That is taking me time, with a lot of trial and error, to get better at. BUT, when you've applied your carb ratios and feel you've done your best YET the bolus hasn't given you that optimum result ... activity not allowed for (or allowed for but not performed) might help explain after the 4 hrs why your BG is not where you planned.
I have found that, after supper/dinner, if I spend even 20 minutes being mildly active rather than finding the TV and comfortable chair, then I can change the probable BG outcome for the evening and night. This depends on what I've eaten - high fat content, slow to digest or fast carbs with low fat; I monitor my BG with Libre 2, careful to not trigger a hypo with activity because the insulin has arrived before the carbs, and once my BG is starting to rise after eating, do something active for a short period. I am not a creature of routine. I don't have specific times for eating or moving (retirement removed those pressures - no longer a rushed breakfast and dash to work) but I am creating generic routines to help manage my BG, such as some relatively mild activity at some point after dinner. It's a balance between becoming a slave to my D management or pragmatic acceptance that D does need some management with some associated inconvenience. Luckily most TV that I watch comes from the recording technology, not live terrestrial TV.
Unfortunately, although the benefit or consequence of activity is based on medical science (activity usually lowers your natural insulin resistance, so the insulin goes further and works more rapidly) it is not easily quantified numerically. There is no generic formula that applies to everyone and this has to be learnt from personal experience. I have learnt ( just) to go with the flow and accept that this is a long haul task managing my D, where not everything goes like clockwork.
