A bone mineral density (BMD) test measures how much calcium and other types of minerals are in an area of your bone.
The test uses X-rays to measure how many grams of calcium and other bone minerals are packed into a segment of bone.
The bones that are most commonly tested are in the spine, hip and sometimes the forearm.
Why it's done
Doctors use bone density testing to:
Identify decreases in bone density before you break a bone
Determine your risk of broken bones
Confirm a diagnosis of osteoporosis
Monitor osteoporosis treatment
Results
Your bone density test results are reported in two numbers: T-score and Z-score.
T-score compares your bone density with that of a healthy young adult.
Z-score compares your bone density with that of other people of your age, sex, and race.
With either score, a negative number means you have thinner bones than average.
The more negative the number, the higher your risk for a bone fracture.
A T-score is within the normal range if it is -1.0 or above.
If your T-score is:
Between -1 and -2.5, you may have early bone loss (osteopenia)
Below -2.5, you likely have osteoporosis.
