Calcium carbonate vs. calcium citrate?

Is one better than the other? I was told to take calcium and magnesium for pms. Someone then told me that calcium citrate is better than calcium carbonate. What's the difference??

Calcium citrate is more readily absorbed by your body

Calcium carbonate is the main ingredient in TUMS, which is taken as an antacid. Calcium carbonate will neutralize the acid in your stomach. Since you need an acidic environment to absorb calcium, if you take calcium carbonate, it will not be absorbed. You also need an acidic environment to absorb vitamin D, which is essential for the uptake of calcium into the bones. So, by taking calcium carbonate, you don't absorb the calcium and you do not absorb vitamin D. This will prove to be detrimental to your health in the long term.

Calcium citrate is better because it does not neutralize the acid in your stomach. It is more easily absorbed and doesn't interfere with the absorbtion of vitamin D.

when i worked in a health food store our sales pitch was ... Calcium citrate for anyone who didn't have acid indigestion or low stomach acid like seniors commonly do, and calcium carbonate if you suffer from acid indigestion.
Personally i haven't found much difference. For pms calcium lactate worked the best for me.

Calcium Malate Citrate is the most absorbable calcium available, calcium carbonate you can get it on hgher amounts but is less absorbable.

There is a big difference between the two as calcium carbonate is regarded as inorganic as the carbonate radical behaves as an inorganic radical even though carbonate (CO3) actually has carbon in it. Calcium citrate is organic and organic supplements are absorbed much better than inorganic supplements.

So calcium citrate (organic) is much better than calcium carbonate (inorganic). There is a difference in price as well as calcium carbonate is much cheaper than calcium citrate. To get the same benefits you need much greater doses of calcium carbonate than calcium citrate (calculated as actual calcium).