This question can be read two different ways. If you NEED an operation it can be done at any time. For instance, if you get appendicitis or a gallbladder attack, you could safely have the surgery at any time after your sleeve gastrectomy.On the other hand, if you want to have a knee or hip replacement, or a hysterectomy, which are generally elective procedures, you would want to wait until you have lost a significant amount of weight. This would allow you (and your surgeon) to enjoy the benefits of a safer, easier operation. In some cases these operations don't even need to be done because the joint pain gets much better or the dysfunctional bleeding stops. Six months is a good amount of time to wait, as much of the excess weight has been lost by this time.