A bone mineral density (BMD) test measures how much calcium and other types of minerals are in an area of your bone.
This test helps your health care provider detect osteoporosis and predict your risk of bone fractures.
Bone density testing can be done several different ways.
The most common and accurate way uses a dual-energy x-ray absorptiometry (DEXA) scan. DEXA uses low-dose x-rays. (You receive more radiation with a chest x-ray.)
There are two types of DEXA scans:
If you are or could be pregnant, tell your health care provider before this test is done.
The scan is painless. You need to remain still during the test.
Bone mineral density (BMD) tests are used to:
You should have bone mineral testing or screening if you have an increased risk of osteoporosis. You are more likely to get osteoporosis if you are:
Women under age 65 and men ages 50 to 70 are at increased risk of osteoporosis if they have:
Current practice recommends BMD retesting every 2 years. However, recent research suggests that some women may be able to wait a much longer time between their screening tests. Discuss with your doctor how often you should be tested.
The results of your test are usually reported as a T-score and Z-score:
With either score, a negative number means you have thinner bones than average. The more negative the number, the higher your risk of a bone fracture.
A T-score is within the normal range if it is -1.0 or above.
Bone mineral density testing does not diagnose fractures. Along with other risk factors you may have, it helps predict your risk of having a bone fracture in the future. Your doctor will help you understand the results.
If your T-score is:
Treatment recommendation depends on your total fracture risk. This risk can be calculated using the FRAX score. Your health care provider can tell you more about this. You can also find information about FRAX online.
Bone mineral density uses a slight amount of radiation. Most doctors feel that the risk is very low compared with the benefits of finding osteoporosis before you break a bone.
Reviewed By: Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial team.