My understanding is that calcium citrate is more easily absorbed than calcium carbonate. I was taking the 600 mg powdered calcium citrate (from Amazon) twice daily along with one vitamin D 2000 mg capsule once daily. BUT I am now working on getting all my cakcium from food that makes me happy. It is not so difficult - I have a list available to refer to for all of the foods that I take or am now taking & if I pay attention, I can reach 1200 mg daily.