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. Bone fracture risk is highest in people with osteoporosis.

Guidelines recommend screening for those who are thought to be at 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:
  • A fracture in any man or woman over age 50
  • 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 the treatment.

The results are used as part of the FRAX scoring system, which considers bone density test results with other fracture risk factors. From this score, you and your doctor can determine whether you might need medication to treat the osteoporosis.

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

While you are lying on a cushioned table, a scanner passes over your body. Typically, the machine takes x-rays of your lower spine and hip. This is called a central DEXA scan. In most cases you won't need to undress.

There are smaller machines that just measure the bone density in your wrist, fingers, leg, or heel. You may find these in pharmacies, shopping centers, and health fairs. However, a central DEXA scan that measures bone density in your lower spine or hip is the best test to predict your risk of fractures.

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

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