If finasteride is so safe, what scientific tests can a person do to check it's affect

[Aonyx262]

There's no easy way to compare a quantifiable value like DHT level to a subjective trait, like libido in one individual. It'd be nearly impossible to do this. That's just how placebo effects can work.

If you wanted to compare DHT levels and # of erections per week/subjective libido scale in a large population size irrespective of finasteride treatment, that may be better, although it would still only give you correlation (if it existed) and not causation. This is more or less what the reports of side effects are by MERCK, but specific to Finasteride treatment without DHT level correllation. Also, since DHT has very little at all to do with the process of erection, you probably wouldn't find much of a correlation. After puberty, DHT mostly just has the wonderful effect of head hair loss, prostate hyperplasia, and body hair growth.

Erection is primarily a function of the parasympathetic nervous system (the "rest and digest", or "feed and breed" part of autonomics), hence why when someone is pretty nervous or anxious(maybe about finasteride treatment), they may have difficulty getting an erection. Of course there are other factors involved with inhibiting 5AR, like the potential to feedback inhibit GnRH or increased levels of estrogens by excess testosterone accumulation, so you could measure these too I suppose, but in YOUR specific case, its not possible to determine YOUR specific cause for your symptoms. Even if you withdraw Finasteride treatment, and all of a sudden you had erections again, that does not mean that Finasteride as a drug was the physiologic reason for your side effects.

And of course, humans aren't machines, and we all respond differently to interruptions in our homeostasis. I havent had any side effects whatsoever as far as I can tell.