Welcome to HealthcareMagic Forum,
You probably are suffering from ANDROGENTIC ALOPECIA
,common type of patterned hair loss or from diffuse hair loss.Its also important to diagnose whether you have thyroid problem or not.You can first try minoxidil
sol 5% topically directly applied to scalp twice a day.Along with this you can start tab finestride 1 mg daily
& biotin once daily .Before taking this you should be under a regular guidance of a dermatologist
.These are very effective medicine but has to be taken for long time.In case you have already lost hair and are suffering from baldness
then you can go for hair transplantation
.But i would say at 21 you are still young for that. You can get details in my website(www.apollobsr.com ) .Improve your diet with green leafy veg, fresh fruits, plenty of water, sprouts ,pulses, high protein diet, avoid items with high sugar content like sweets & chocolates, less of Chinese foods, less of pizza & burgers ,more of milk & ghee, dry fruits . Good sleep also has a important role to play .