Formulation:

Supplemental calcium is usually recommended when dietary calcium is insufficient, and it is most frequently found as calcium carbonate and calcium citrate.^[1][2] Forms of calcium supplements that may also be available include calcium phosphate, calcium lactate, calcium gluconate, and coral calcium.^[1] Different forms of oral calcium supplements have their own benefits and drawbacks. Coral calcium and calcium citrate, for example, may be better absorbed than calcium carbonate. Calcium carbonate is, on the other hand, less expensive than other forms, making it more accessible.^[3][4] Standalone calcium citrate supplements may be more readily used by the body than calcium carbonate. The exception to this seems to be in calcium-fortified foods, where calcium carbonate is absorbed better.^[5]

Range of dosages studied:

Current meta-analyses have reported on studies that cover a wide range of calcium supplementation dosages, from a low dose of 162 mg per day all the way up to 7,700 mg per day. In many of these studies, calcium was taken with vitamin D3 ranging from 400 to 1,000 IU per day. Ranges studied for skeletal health, pregnancy-related concerns, digestion, metabolism, and body mass are similar (about 200 to 2,000 mg per day), but cardiovascular health uses a higher range (500 to 7,700 mg per day).