A calcium deficiency could be a contributing cause of bone loss and bone loss disorders (osteoporosis and osteomelacia in adults; rickets in children), depression, diuretic therapy, back and leg pains, fatigue, heart disease, heart palpitation, hypertension, inflammatory bowel disease, insomnia, intestinal resection, malabsorption, malnourished, muscle cramps and spasms, muscular and nervous irritability, menstrual cramps, osteoarthritis, periodontal disease, premenstrual syndrome, steatorrhea, tetany, tooth decay, and very high fiber intakes. Magnesium deficiency causes various abnormalities in calcium metabolism and ingestion of foods high in phosphorus (soft drinks and animal protein) promote the urinary loss of calcium. This can cause the body to leach calcium from the bones and thus contribute to osteoporosis. Caffeine, excess dietary fat and fiber, and lack of exercise can also negatively influence calcium status. In addition, pregnant and lactating women have an increased requirement for calcium, as do women of all ages.

In atherosclerosis, intracellular calcium is often elevated, leading to calcium deposits which indicate inadequate calcium metabolism rather than an absolute deficiency or excess. Many calcium-regulated intracellular events are inadequate in atherosclerosis. Paradoxically, improved intracellular calcium status normalizes inadequate cellular functions. Ionized serum calcium helps to initiate muscle contractions. As such, it plays a vital role in the contraction-relaxation cycle that regulates a normal heart beat; ionized calcium also regulates the passage of fluids across cellular membranes by affecting cell wall permeability. Calcium also closely interacts with magnesium in cardiovascular health.

Pharmaceutical drugs that can cause a calcium deficiency include aluminium hydroxide, barbiturates, bumetanide, chlortetracycline, cholestyramine resin, cimetidine, corticosteroids, demeclocycline, digoxin, doxycycline, etharynic acid, ethosuximide, famotidine, fosphenytoin, furosemide, hydrochlorothiazide and triamterene, magnesium hydroxide, magnesium oxide, magnesium sulfate, methsuximide, mineral oil, minocycline, nizatidine, oxytetracycline, phenytoin, primidone, ranitidine bismuth citrate, ranitidine hydrochloride, tetracyclines, torsemide and triamterene.

Dietary sources richest in calcium (per serving) include bone meal, broccoli, dark green leafy vegetables, legumes (beans, lentils, peas, soybeans), milk and milk products, nutritional supplements, nuts, salmon, sardine, tofu and whole grains and grain products.