Possible side effects of Finasteride

The overall incidence of sexual function disorders in phase 3 trials of finasteride 1mg was 3.8% in those receiving the medication vs 2.1% in those receiving a placebo. [2] Of the 3.8%, known possible side effects, including a decrease in libido (sex drive), a decrease in the amount of semen, and trouble getting or keeping an erection. 

Other side effects may include: breast tenderness, depression, anxiety, rashes, testicular pain, and neurological issues like mental fogginess.

Finasteride can interfere with PSA (Prostate-Specific Antigen) lab tests. This is used in screening for prostate cancer. You should tell your physician that you are taking finasteride if you have a PSA test done, as finasteride can affect PSA levels. Any changes in PSA levels will need to be evaluated by your physician, even if the test results are still within the normal range for men not taking finasteride. For more information or if you have concerns, talk to your healthcare provider.