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

Followed, this answered three questions I had. Side effects was my main issue with personal messages too.

How do you tell the difference between the drug working and just a good week? Same for me with vitamin D during illness, unfortunately.

Is it normal to feel worse before better? Nobody told me that.

How do you tell the difference between the drug working and just a good week?

Is a baseline blood test really necessary before starting something like this? Same for me with alpha-GPC, unfortunately.

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