Is it pills / vitamins doctors can prescribe you if you have thin hair so that your hair can get thicker ?

Not really: Has your hair always been thin? If so, that,is your hair. If it has recently thinned, your diet or health could be responsible. Also, stress causes hair,loss and thinning so if,that is the case and you reduce your,stress level, it will likely return to normal. Some sources suggest nioxin or rogaine (minoxidil) to increase hair growth. Biotin is a suggested supplement. A good diet is your best bet.