Definition of Bone mineral density test:

A bone mineral density (BMD) test measures how much calcium and other types of minerals are present in a section of your bone. Your health care provider uses this test, along with other risk factors, to predict your risk of bone fractures in the future and detect osteoporosis. Bone fracture risk is highest in people with osteoporosis.

How the test is performed:

Several different kinds of machines can do BMD testing. The most common and most accurate method is called a dual-energy x-ray absorptiometry (DEXA) scan. It uses low-dose x-rays (about 1/10th the radiation dose of a chest x-ray).

There are two different types of DEXA scans:

• Central DEXA. While you are lying on a cushioned table, a scanner passes over your lower spine and hip. In most cases you won't need to undress.
• Peripheral DEXA (p-DEXA). These smaller machines measure the bone density in your wrist, fingers, leg, or heel. You may find these machines in doctor's offices, pharmacies, shopping centers, and health fairs.

A central DEXA scan that measures bone density in your lower spine or hip is the best test to predict your risk of fractures.

How to prepare for the test:

Remove any jewelry before the BMD test. Inform your health care provider if you may be pregnant.

How the test will feel:

The scan is painless, although you will need to remain still during the test.

Why the test is performed:

Bone mineral density (BMD) tests are used to detect osteoporosis, the thinning of bone tissue and loss of bone density over time.

BMD testing or screening should also be done in the following people, who are thought to be at an increased risk for osteoporosis:

• Women over age 65 and men over age 70
• Women under age 65 and men ages 50 - 70 who have risk factors such as:
  • Bone fracture caused by normal activities, such as a fall from standing height or less ("fragility fracture")
  • Chronic rheumatoid arthritis, chronic kidney disease, eating disorders
  • Early menopause (either from natural causes or surgery)
  • History of hormone treatment for prostate cancer or breast cancer
  • Significant loss of height (See: Compression fractures of the back)
  • Smoking
  • Strong family history of osteoporosis
  • Taking corticosteroid medications (prednisone, methylprednisolone) every day for more than 3 months
  • Three or more drinks of alcohol per day on most days

If you are being treated for osteoporosis, BMD testing can help your health care provider monitor your response to treatment.