Serum Calcium may change with kidney or parathyroid diseases, cancer, antiestrogen therapy, sarcoidosis, tuberculosis, and other conditions, but it does not change with higher or lower dietary calcium intake, so it cannot be used as a nutritional excess or deficiency indicator. In the event of a dietary deficiency, the body simply covers calcium requirements from bone reserves. Other methods to assess someone's calcium status include a 24-hour urine collection, or a bone scan. The latter does not measure calcium specifically, but assesses overall bone density, which reflects the total content of all other minerals present in bone as well... Full Text