BMD test; Bone density test; Bone densitometry; DEXA scan; DXA; Dual-energy x-ray absorptiometry; p-DEXA; Osteoporosis - BMD
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:
The scan is painless. You need to remain still during the test.
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 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 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.
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 (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:
Chapurlat RD, Genant HK. Osteoporosis. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 69.
Committee on Practice Bulletins-Gynecology, The American College of Obstetricians and Gynecologists. ACOG practice bulletin n. 129. Osteoporosis. Obstet Gynecol. 2012;120(3):718-734. PMID: 22914492
Cosman F, de Beur SJ, LeBoff MS, et al; National Osteoporosis Foundation. Clinician's guide to prevention and treatment of osteoporosis. Osteoporos Int. 2014;25(10):2359-2381. PMID: 25182228
De Paula FJA, Black DM, Rosen CJ. Osteoporosis and bone biology. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 29.
Kendler D, Almohaya M, Almehthel M. Dual x-ray absorptiometry and measurement of bone. In: Hochberg MC, Gravallese EM, Silman AJ, Smolen JS, Weinblatt ME, Weisman MH. Rheumatology. 7th ed. Philadelphia, PA: Elsevier; 2019:chap 51.
US Preventive Services Task Force, Curry SJ, Krist AH, Owens DK, et al. Screening for osteoporosis to prevent fractures: US Preventive Services Task Force recommendation statement. JAMA. 2018;319(24):2521-2531. PMID: 29946735
Review Date: 1/14/2018
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. Editorial update 08/01/2018.
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Call 9-1-1 for all medical emergencies. Links to other sites are provided for information only—they do not constitute endorsements of those other sites. © 1997-2010 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.