What is a Bone Density Test?

Bone density testing (DEXA) determines if you have osteoporosis — which can cause bones to become more fragile and more likely to break.

It is a common misconception that bone is a hard, lifeless structure. Actually, bone is a complex, living tissue whose growth is affected by diet and exercise. The body is constantly building new bone tissue while breaking down or resorbing old bone. Until around age 30, the body builds and stores bone efficiently and total bone density is increasing or constant.

Later in life, the body’s bones begin to break down faster than new bone can be formed. In women, bone loss accelerates after menopause, when the ovaries stop producing estrogen, a hormone that helps maintain bone density. Bone is living tissue that is continually damaged by osteoclasts (cells responsible for destroying bone) and rebuilt by osteoblasts (cells responsible for bone repair). If this destruction/reconstruction process is unbalanced and bone loss is severe women may experience symptoms of osteoporosis.

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.

How Should I Prepare for My Bone Density Test?

Do not consume any solid pills containing calcium for 24 hours before your test. You should not have had any IV contrast, barium studies or nuclear medicine tests for three weeks before testing.