Looking on the net the highest dose you can buy over the counter doesnt come near the 300mg that has been used with positive results regarding MS. I’m more interested in trying it for the MS symptoms rather than a hair product.
You need pharmaceutical grade biotin and definitely not over the counter stuff, as you will be taking 30 pills per day and rather a lot of filler. The facebook group probably has all the information you need. Biotin for Progressive MS | FacebookMD1003 (biotin) | MS Trust
Most people seem to buy the powder form from America, although it is possible to buy capsules in Europe, but they are more expensive. The files in the facebook group should have up to date details. I think the trial dose was 100mg x 3 per day. There were a couple of people on the PPMS board that reported getting good results and might be worth doing a search. Effect of MD1003 in Progressive Multiple Sclerosis (SPI2) - Full Text View - ClinicalTrials.gov