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What Does a Bone Density Test Tell a Person?

A bone mineral density (BMD) test is a procedure that uses X-rays to gauge bone health and determine an individual's risk for developing the bone disease called osteoporosis.

  1. The Facts

    • During a BMD test, a special device called a central dual-energy X-ray absorptiometry (DXA) machine measures the bone mineral content of the hip and spine, which are susceptible to osteoporosis, according to the National Osteoporosis Foundation.

    T-Score

    • Doctors usually report the results of a BMD with a reading called a T-score, which compares your bone density with that of a hypothetical healthy young adult of the same gender, according to the Mayo Clinic. A T-score gauges your similarity to this average value in units called standard deviations (SDs).

    T-Score Results

    • If your test results yield a T-score above -1 SD, you have normal bone density, reports the Mayo Clinic. Results between -1 and -2.5 SDs indicate below average density that may lead to osteoporosis, while results below -2.5 SD indicate active osteoporosis.

    Z-Score

    • Your doctor may also use a Z-score, which compares your bone health to others of similar age, ethnicity, weight and gender, notes the Mayo Clinic.

    Z-Score Results

    • The Mayo Clinic notes that a Z-score of less than -1.5 SD may indicate unusual underlying causes for bone loss.

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