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

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

Is a baseline blood test really necessary before starting something like this?

Did not know half of this. Thanks. Same for me with nested quotes, unfortunately.

Is it normal to feel worse before better? Nobody told me that. Same for me with a partial order, unfortunately.