I am 20 years old, taking Finasteride for hair loss for the last 6 months. Is it safe?

Finasteride blocks about 60% of circulating DHT by blocking 1 of the 3 DHT receptors. Most people taking finasteride do see some results and about 10% of those taking it experience side effects.  If you are interested in seeing better results with lower incidence of side effects I would recommend seeing a hair loss specialist who focusses on stopping hair loss and regrowing hair who can recommend more effective solutions than Finasteride.