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 for bone fractures.
Bone density testing can be done in several 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 from a chest x-ray.)
There are two types of DEXA scans:
If you are or could be pregnant, tell your provider before this test is done.
DO NOT take calcium supplements for 24 hours before the test.
You'll be told to remove all metal items from your body, such as jewelry and buckles.
The scan is painless. You need to remain still during the test.
Bone mineral density (BMD) tests are used to:
Bone density testing is recommended for all women age 65 and older.
There is not full agreement on whether men should undergo this type of testing. Some groups recommend testing of men at age 70, while others state that the evidence is not clear enough to say whether men at this age benefit from screening.
Younger women, as well as men of any age, may also need bone density testing if they have risk factors for osteoporosis. These risk factors include:
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 for 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 for having a bone fracture in the future. Your provider 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 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 experts feel that the risk is very low compared with the benefits of finding osteoporosis before you break a bone.
Reviewed By: John D. Jacobson, MD, Professor of Obstetrics and Gynecology, Loma Linda University School of Medicine, Loma Linda Center for Fertility, Loma Linda, CA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.