Suggest Remedy For Premature Graying Of Hairs

I have greying of hairs and my age is 19. The dermatologist prescribed me to take curlzvit for a month and go for a check up after that. I have the correct levels of haemoglobin, thyroid, vitamin D3 and B12. Will my grey hairs be turned to normal aftee this medication ? After the complete treatment of 3 months, will the problem of greying be gone forever ? I am very concerned as earlier also I tool medication for this but that time the tablet given was different and after 2 years again my hairs became grey. So will it be cured permanently this time with a treatment of curlzvit for 3 months ?