Hi Kerriann, I use 15mg mirtazapine, for me it stopped all the anxiety,palps,etc by day one ! Also I slept well straightaway. There was a settling in period of about 10 days which took the form of extreme tiredness during the daytime but each day it got less,so by day 10 it was fine. As I d been so bad with anxiety,palps,etc for so long this didn't unduly bother me it was a welcome relief ! All people will be different though but it worked for me and as gp will not perscribe sleeping tablets long term this sorted out 2 issues for me anxiety and insomnia.