My doctor said the protein shakes are harsher on the stomach when they are premixed or mixed with milk. He told me to make my own protein shakes with celebrate 4 in 1 with water and not milk to start out with. I dont know if it makes a difference or not because I haven't tried it with milk yet. I am keeping this protien down though. So maybe there's something there, maybe not. Good luck. Hope u find your happy medium. Sent from my SM-G975U using BariatricPal mobile app