Hi,
Depends on the carb content & posibly any fat in the meal delaying digestion?
Rule of thumb, 20 minutes.
To complicate things further, the other day, I ate at the tail end of a correction dose & injected just prior to picking up the fork.
Had a lovely flat line on the graph in the 5s.
Some folk might inject after for larger amounts of protien, or if they had simply forgotten to do it prior?
It's about getting that insulin working profile to suit your requirements.