You should not need or benefit from supplements if you have a balanced diet and no relevant health conditions (hormonal, digestive etc).Micronutrients work synergistically and in opposition, if you randomly supplement them individually or in small groups you can actually do more harm than good for your health and wellbeing by setting up imbalances. Most clients I see are not eating anywhere near enough oily fish, bright and dark coloured produce, nor mineral rich foods like beans, lentils, nuts and seeds.
If you believe your diet to be low in biotin the obvious solution is to overhaul your diet - this will supply the full complement of nutrients you need for your body to function optimally. Everything from restful sleep to high energy during workouts to hormone balance to healthy skin (including follicles).
If you do want to a targeted supplement regime the best person to consult is a registered dietician or someone else who has studied nutrition at degree level. Many doctors know a limited amount about the topic or don't keep up to date with the latest research (medicine and allied fields is too huge to know everything about everything).
2a-2c, medium texture, porous/ colour treated. Three years CG, growing out mechanical and chemical damage = breakage and very high porosity. Past armpit length heading for waist.
Treatments: Komaza protein, Komaza Matani, coconut oil with sugar syrup. Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss ultimate volume
Styler: Umberto Giannini jelly, Boots curl creme, Rockin RInglets
Experimenting with: Mega-Tek, Curl Harmony reviver, Elvive Full Restore 5.