While insulin on its own barely does anything at all!
Although every day is a bit different.
I had my usual 40 g carb breakfast today 20 minutes after bolus (4 units) and went to work, watching Dexcom climb and climb and climb over from a start of 5.9, up to 8, 10, 12, 14… then I decided to go down the stairs (5 flights) and back up again. Within 20 minutes, Dexcom shows it’s back below 10 and not long afterwards down-arrowing to 5.5. Needing an emergency butter tart.
Don’t worry: tomorrow will be something different.