Careful with ester C, id stick with ascorbic acid or sodium ascorbate. Its more than just complaining kidneys. Without adequate vit A,D,K calcium doesnt end up where it needs to be (ie bones and teeth) and start to calcify soft tissue.
Generally speaking, unless you have a known calcium deficiency supplementing calcium outside of what may be in your multi generally does more harm than good. Dr Levy has a new book out called ":Death by calcium". Taking D will also likely increase your need for Magnesium and can be toxic if not combined with ample amounts of vit A and K. A ratio of 5:1 A to D is a good place to be. Cod liver oil has a good A to D ratio.