Stupid question: how do you know whether what is in the vial matches the label at all?

Followed, this answered three questions I had.

Following this because I am in the same place and have no idea what to ask at the appointment.

How long before you can reasonably say something is or is not doing anything?

Sorry, probably obvious, but where do you even start with something blank?

How do you get a clear photo of an imprint? Mine keep coming out blurry.