Calcium Citrate Plus D3 formula provides you with 315 mg of calcium citrate and 250 IU of D per tablet. Calcium in the form of calcium citrate helps support bone health and vitamin D3 helps your body absorb calcium. 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). It may also be used in certain patients to make sure they are getting enough calcium (e.g., women who are pregnant, nursing, or postmenopausal, people taking certain medications such as phenytoin, phenobarbital, or prednisone). Calcium plays a very important role in the body. It is necessary for normal functioning of nerves, cells, muscle, and bone. If there is not enough calcium in the blood, then the body will take calcium from bones, thereby weakening bones.