It may be used to treat conditions caused by low calcium levels such as bone loss (osteoporosis), weak bones (osteomalacia/rickets), decreased activity of the parathyroid gland (hypoparathyroidism), and a certain muscle disease (latent tetany).
Calcium. Taking calcium at night does not affect your sleep but can reduce the effectiveness of another supplement, magnesium, which promotes relaxation and is often recommended to be taken at night. Because calcium and magnesium compete for absorption, they should not be consumed at the same time.