Is it necessary to do PRP after hair transplant? I'm 2 months now. My doctor is telling me to go for PRP

PRP is not necessary after a hair transplant surgery. If your doctor is recommending it, then follow up with your doctor.  We have offered PRP for over two years after hair transplant surgery and did not see remarkable difference. 

PRP combined with hair transplant in our experience leads to better results than without PRP. We usually recommend PRP after surgery only if we want to support the non transplanted hair. So, if you are still suffering from hair loss or having hair thinning in the non transplanted hair area, then you can go in for PRP....

PRP is not dangerous but has little strong science behind it to date.  It can not hurt you, so if it is free then it may not be bad. 

There have yet to be any published medical studies looking at the combination of PRP and hair transplantation - but there certainly have been studies looking at the benefits of PRP.PRP has the potential to promote faster growth. Whether it enhances survival of grafts is still unknown. It may also help keep your existing hair growing (rather than progressing to further thinning).All in all many surgeons are investigating PRP combined with hair transplantation - the key step now is to design careful studies to really figure out how much it helps.