I've lost a lot of my sense of taste and smell. i started taking finasteride in january. could that be a side effect?

Smell and taste : Smell and taste are closely related. Often when people lose both, it is really the sense of smell that is lost, which in turn affects taste. Nasal congestion could be a factor. Your medicine is known to affect nasal congestion, but there are no reports of it affecting smell or taste, at least that I can find. If the medicine is the cause, a holiday from the medicine may be needed to be sure.