Ya know Steve, its all a matter of convience and life style. There are lottsa days I end up taking my shot AFTER a meal because Im not home and taking it post meal is better than not taking it at all. YES, many of the functions that Byetta has are better if you give the drug 15-20 mins to get into your blood stream, but lots of times, lifestyle just doesn't allow us to be that rigid.
But the ultimate answer to your question is yes, take your shot and give it some time to work before you eat. And if you are going to be that strict, remember to take your oral meds at least 45 mins before you take your shot.
Well, typically metformin is prescribed to be taken "with a meal" and actos or any of the sulfonylaureas are presribed to be taken half an hour "before a meal". The reason for actos prior to a meal is simply so it can start stimulating insulin production to ameliorate any spike in blood sugar you have due to your meal. The metformin which takes longer to work and simply is there to break down your insulin "resistence" can be taken with the meal so that 1) it doesnt upset your stomach and 2) you get potentially better absorbtion of the drug.
Now the big problem comes when you take Byetta in that it has an action that delays the emptying of the stomach contents to smooth out your blood sugar spikes. If your meds get caught up in this mechanism, they aren't doing what they're supposed to do WHEN they're supposed to do it! So if at all possible (and timing is not always easy if you have a busy lifestyle) take those meds before you eat and before or at the same time you do the injection. (before is better). This will get the oral meds into your blood stream before Byetta has a chance to trap them. Hope this helps.