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.
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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