Bone densitometry, or bone density testing, uses low energy x-rays to precisely measure the mineral content of the bones in your arms, hips, and spine, from which your doctor can determine their thickness and strength. The test lasts only 15 to 20 minutes, during which time you will have to lay still on your back with your arms at your sides.

The results will tell you if you have normal bone mineral density (BMD), osteopenia, which is thinning bones, or osteoporosis, which is more advanced thinning of the bones. Bone density tests are also used to determine how well the medication you are taking to prevent or reverse these bone-thinning conditions is working.

Your test result will include a T-score that compares your bone density with that of younger adults of the same race and sex. It will also include a Z-score that compares your bone density with others who are the same age, race and sex.

What the Numbers Mean:

  • A positive T-score, or a negative score up to -1.0 means your bones are in good shape.
  • A negative T-score means your bones are weakening.
  • A negative T-score between -1.0 and -2.5 means you have low bone mass, or osteopenia
  • A negative T-score below -2.5 means you have very low bone mass, or osteoporosis.

How Often to Test Bone Density

A study published in the January 2012 issue of New England Journal of Medicine found that women who still have very good bone density at the age of 67 can wait up to 15 years to be screened again. The reasoning behind this recommendation—which contrasts current recommendations that all women ages 65 and older be screened routinely for osteoporosis—is that it will take about 15 years for most women with strong bones to develop osteoporosis.

At the same time, the researchers predict it will take about five years for women with moderate osteopenia to develop osteoporosis and only about one year for women with advanced osteopenia. Your doctor is the best person to determine which category you fall into and how often you should undergo bone density testing.




Gourlay, M. et al. "Bone-Density Testing Interval and Transition to Osteoporosis in Older Women." New England Journal of Medicine January 19, 2012; 366:225-233. Web June 2012

Harvard Medical School: Bone Density Test for Osteoporosis

Wexner Medical Center: Osteoporosis
osteoporosis/Pages/index.aspx Web June 2012