At my visit today I asked my surgeon about the types of calcium. He explained that citrate is preferred because you don't need stomach acid or food to help with the absorbtion process. Carbonate needs stomach acid and/or food in order to absorb. For the first 6 months, most of us are on acid blockers so some may be absorbed, just not as much/as well as citrate. Also, whichever you take you need to include vitamin D for absorbtion. This usually isn't a problem since most calciums also incluide D. I have taken calcium citrate for years because I didn't have to take it with food. Sorry if I ruffled anyone's feathers. Take whatever you and your medical team are ok with. I believe most of us want to be helpful sharing what we have learned through experience, MD instructions and research. We all learn from each other. If anyone is interested, this article has more information re calcium post WLS
http://voices.yahoo.com/how-choose-best-calcium-supplement-after-a-4842152.html