Dual-energy X-ray Absorptiometry (DEXA) is a quick, accurate and painless test for measuring bone loss. The test uses very low dose X-rays (about 10% of that used for a chest X-ray) and is considered the established standard for measuring bone mineral density (BMD). The test compares the bone mass in your lower spine and hip with that in a young adult of the same gender, as well as with the bone mass of these sites of other people in your age group of the same gender and of similar size. This test is more sensitive than tests performed on portable devices that measure only the wrist, fingers or heel. In addition, this test is useful to monitor therapy, which some patients may require. Tests performed on the portable machines cannot accurately monitor therapy response.