Calcium Citrate
Calcium Citrate is a tier 1 form of Calcium, used in 1,067 on-market products and providing 21.1% elemental calcium by weight.
1,067
on-market products
tier 1
quality tier
21.1%
elemental fraction
Basis: Ca3(C6H5O7)2 x 4H2O, tetrahydrate (USP-standard commercial form)
Why this tier: Meta-analysis of 15 studies (184 subjects): absorption significantly higher than carbonate by ~20-27% (27.2% fasting, 21.6% with meals). Citrate absorption is generally considered less dependent on gastric acid (general pharmacology, not from the abstract).
Source: Sakhaee K et al. 1999, PMID 11329115