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

Worth repeating that this is not medical advice and the answer often depends on who you are.

What do you do about the fee? Do you just pay it?

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

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

What is the first thing you would read if you were starting from zero?

Sorry for the basic question, but how do you actually start one of these diaries?