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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.
BMD test; Bone density test; Bone densitometry; DEXA scan; DXA; Dual-energy x-ray absorptiometry; p-DEXA
Bone density testing can be done several different ways.
The most common and accurate way uses a dual-energy x-ray absorptiometry (DEXA) scan. It uses low-dose x-rays. You receive more radiation with a chest x-ray.
There are two different 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 will 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 for osteoporosis. You are more likely to get osteoporosis if you are:
Women under age 65 and men ages 50 - 70 are at increased risk for osteoporosis if they have:
The results of your test are usually reported as a "T score" and "Z score."
In either score, a negative number means you have thinner bones than the standard. 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. However, 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.
Treatment recommendations depend on your total fracture risk.
Bone mineral density uses a little bit of radiation. But most experts feel that the risk is very low compared with the benefits of spotting osteoporosis before you break a bone.
Simple bone density scans using portable machines may be available as part of health fairs or screenings. These portable scanners may check the density of your wrist or heel. However, keep in mind that hip and spine scans are more reliable.
U.S. Preventive Services Task Force. Screening for osteoporosis: recommendation statement. Am Fam Physician. 2011 May 15;83(10):1197-200.
Lim LS, Hoeksema LJ, Sherin K; ACPM Prevention Practice Committee. Screening for osteoporosis in the adult U.S. population: ACPM position statement on preventive practice. Am J Prev Med. 2009;36:366-375.
National Osteoporosis Foundation. Clinician's Guide to Prevention and Treatment of Osteoporosis. Washington, D.C.: National Osteoporosis Foundation; 2008.
Nelson HD, Haney EM, Dana T, Bougatsos C, Chou R. Screening for osteoporosis: an update for the U.S. Preventive Services Task Force. Ann Intern Med. 2010;153:99-111.