A Bone Density test determines if you have osteoporosis — a disease that causes bones to become more fragile and more likely to break.

In the past, osteoporosis could be detected only after you broke a bone. By that time, however, your bones could be quite weak. A Bone Density test makes it possible to know your risk of breaking bones before the fact.

A Bone Density test uses X-rays to measure how many grams of calcium and other bone minerals are packed into a segment of bone. The bones that are most commonly tested are located in the spine, hip and forearm.