Calcium is most commonly associated with bone and dental health, and a deficiency in this mineral can lead to dental decay, osteopenia, and ultimately, osteoporosis. However, calcium also plays an important role in blood clotting, blood pressure, nerve signaling, and cell communication. Having poor hydrochloric acid (stomach acid) can impact calcium absorption, as can the presence of other minerals such as magnesium. Arguably most important is having optimal levels of fat-soluble vitamins D and K. Vitamin D helps with calcium absorption, and vitamin K regulates calcium concentrations in the body and pulls calcium into the bones.