Depends on the mg per ml, but 30 ml could last you 6 weeks if you do 5 on 2 off, otherwise, yeah, I'd get 2 bottles and run it 8 weeks (I'm on day 11 right now with no vision sides and I'm going to try to run it as long as I can and see if the vision thing wouldn't even affect me after doing 5 on 2 off last time I ran it).