A bone density test is used to diagnosis osteoporosis, which is a disease that causes weakening of the bones ultimately resulting in fractures. In the past, osteoporosis could only be detected after a person's bone broke; however, by using a bone density test, it is possible to know one's individual risk of breaking bones before one breaks.

A bone density test uses X-rays to measure the amount of calcium and other bone mineral packed into the segment of bone. Common areas that are tested using a bone density scan include the spine, hip, and forearm.