Four capsules of the Lithothamnium provide 3080 mg of lithothamnium powder, of which 2156 mg is calcium carbonate. Approximately 40% of this consists of elemental calcium, which amounts to 862 mg. This is a fairly common and completely safe dosage of calcium. The Recommended Daily Amount is 800 mg, so the amount mentioned above is about 108% of the RDA, which is a good quantity.

Rennies is a registered over-the-counter medication. Lithothamnium is a dietary supplement intended as a source of calcium for bones and teeth. We cannot recommend this dietary supplement for the condition you mention. There is also no data available on which we could compare the two in terms of their effects and side effects.

The warning on the Rennies packaging (see below) theoretically applies to all products with a high percentage of calcium, but this statement is not legally required for dietary supplements. The warning on the Rennies packaging is as follows: "Do not use in cases of severe kidney dysfunction and/or kidney stones, low phosphate levels in the blood, excessively high calcium levels in the blood, hypersensitivity to any of the ingredients."

Rennies is a very mild over-the-counter medication. The ingredients calcium carbonate and magnesium oxide are also found in many dietary supplements and in nature (for example, in oyster shells, eggshells, coral, and rock).