Will a 3rd injection of sculptra be useful 4 - 5 months after the 2nd injection?

Without examining you or seeing photographs of you, it is difficult to give you advice as to why you may not be seeing much in the way of results after your second Sculptra treatment.  In general, it normally does take several treatment sessions to obtain the desired result and it is not unusual that three or four sessions might be needed.  Depending on the baseline appearance, it sometimes even takes more sessions.  I normally recommend waiting at least one month in between treatments, but there is no problem with waiting a longer period of time.  So, I do not think you have waited too long to have a third treatment.  For most people, having more treatment sessions leads to more added volume.  

If we're talking about your face then I can tell you that in my practice the average patient gets 6 vials of Sculptra to achieve the best results. These are injected 6 to weeks apart. I also treat their skin with skin care, and microneedling PRP, Botox, and other fillers. If we're talking about the buttocks then you might need 10 to 6 vials. Best wishes

Hello and thank you for your question.  We typically recommend one vial per decade for the face.  It can take three to six months to see results with Sculptra. We offer combination treatments with Sculptra, including our Skin Medica Skin Care line, fillers,  Ultherapy and ResurFx.  This gives our patients the benefits of some immediate results while also encouraged to understand the Sculptra is hard at work!  I hope this information helps and best of luck to you!