I regrew my hair with a high dosage combination of biotin, vegetal silica and zinc about six years ago.
The hair loss cause was stress and I felt that getting rid of the stress was also essential to the program. Hair loss stopped the day I started the nutrition regime and since hair grows on average about a half inch per month I saw evidence of new hair growth in about 4 weeks. I had gone almost all silver grey/white(stress?) before the hair loss started but all new growth came in with my natural brown color(no more stress?). Six years later I still have a full head of hair with some little flecks of white/grey at the crown(various degrees of stress or poor circulation?).
I continued my nutrient program for about six months but tapered the dosage down a bit after the first 2 months and further at the 4 month point. Hope this helps.