How long before I can get a second BBL?

Thanks for your question. There is no hard and fast rule that determines when you can have any revisionary surgery. I usually wait at least 6 months because at that point, most of the fat cells that have survived are stable and good to go. This also means that swelling and inflammation have resolved and a determination of your final shape can be made. The other thing to consider is if you have the fat necessary to perform the second BBL. 

Hello. I recommend at least six months before getting a BBL revision, so a year would be perfect. There is always some initial volume lose due to some fat not surviving, but results should last for ever as long as you keep the weight. A second round BBL is very common and it can easily address your issues, if you have the right build and enough fat for it. But, it is hard to say if it will work for you without photos. Please post a follow up question with photos for a more specific answer. 
Best wishes,

Time is on your side.  After 6 months, the buttock tissue has for the most part returned to baseline as far as taking on new fat injections.  How the fat is harvested and processed determines how much of it survives and hope you had at least half of it survive from your first surgery.  Good luck.