I am 23 and have a poor sex drive and a poor erection. I am also losing hair. My question is can I take finasteride?

The frequency of Erectile Dysfunction in men in their 20s is about 20%. Also, it is not unusual nor abnormal not to have a good sex drive. If you are worried about it, see a doctor and get your testosterone level checked to see if it is hormonal. The impact of finasteride is independent upon your original sex drive and erectile function if you decide to take it.  It all depends upon the importance of your sex drive to you, independent of your hair loss and the treatment of it.