Hi rooby.
I have been taking Mirtazapine for approx 6 years. I started on 15mg but went up to 30mg after a week or 2, I then went up to 45mg when I was going through a tough time. I was taking 45mg for quite some time before going back to 30mg. I have gone back up to 45mg following a recent crisis.
I was told that 15mg was the starting dose and the theraputic dosage was 30 -40mg, but that may have been what my psychiatrist thought was right for me. They do help me a lot but I take them along side other medications - remember everyone is different
Take care xx