I've done it Prework out and it's fine. I use humulin R. Definitely better pumps/fullness and you still benefit postwork due to longer life. My protocol has been 1 hour before workout eat a meal, 20 min prework inject insulin, immediately after took my BCAAs and 7-10g of carbs (vitargo/karbolyn) for every IU. During workout, mixed vitargo with intraworkout BCAAs and sipped during workout. Postwork drank my protein shake and within the hour had another meal. Hope this helps.