I am 21 and want a hair transplant

The real question is what will be your final hair loss pattern and will you have enough hair to follow the loss to its normal completion?  Men under 25 are not good candidates for hair transplants.  I consider doing a hair transplant on a 21 year-old the equivalent of malpractice on the part of the doctor. I would recommend that you seek other alternatives while your final balding pattern is established.  Keep yearly contact with a caring doctor who will build a Master Plan for you, measuring your hair loss and possibly placing you on a drug like Finasteride which is very effective at stopping and often reversing hair loss in young men of your age. Just imagine, doing a transplant now, then losing more hair and doing another transplant in a year, then losing more hair and doing another transplant again in a year so by the time you are 24, you could have had 3 transplants and may continue to bald. The cost in using up your hair bank and your money bank are both the types of discussions you and your doctor must have when building a Master Plan for your future hair loss