I was at 900 and wanted to get off it just because of having to drink so much water. I noticed a difference at 600 with a little more anxiety/agitation that got worse and worse until I realized I was only taking 300. I got some pill boxes to keep it straight and once I was at 600, things evened out. I feel okay at 600, which is good enough for now. It showed me that the stuff helps, as much as I didn't want to admit it.