Low Vit D levels seem to be a common theme for us. I had low levels, and am taking 2000 in the morning and 2000 in the evening. I have almost gotten my levels to optimal. Will probably have it checked again in a few months. I just ran across this article the other day, which is concerning, that the levels on the bottle aren't always accurate. Maybe you could try switching brands for a few months and see if it helps?