Reading a DXA report: T-scores, Z-scores and the next question
Understand the numbers on a bone-density report without treating one score as your complete fracture risk or treatment plan.
Written and evidence-checked by the VeriNourish Editorial Team against 3 named sources listed below. No licensed clinician reviews this content.
A DXA report compares your bone mineral density with reference groups. Its T-score or Z-score helps interpret that measurement; neither is a percentage of bone you have lost. The result belongs alongside your age, fracture history and other risk factors when you discuss treatment (NIAMS).
Cover illustration: Bring the full report to the discussion, including the measured sites. This scene does not show a real scan or patient result.
Find the score that applies to you
For postmenopausal women, clinicians generally use T-scores. Before menopause, Z-scores are generally preferred; they compare with an age-matched population. A Z-score of -2.0 or lower is described as below the expected range for age. Do not apply the postmenopausal T-score categories mechanically to a younger woman's Z-score (ISCD).
For postmenopausal women, a T-score of -2.5 or lower at an accepted measurement site can support a diagnosis of osteoporosis. Common diagnostic sites include the lumbar spine, total hip and femoral neck, with the forearm used in some circumstances. These criteria concern bone-density classification, which is distinct from a complete fracture-risk assessment (ISCD).
Our osteoporosis guide explains the broader condition. On this report, start by circling the site and score the clinician is using rather than trying to average all the numbers yourself.
Why the hip and spine may differ
DXA commonly measures the hip and spine. The readings are site-specific, and interpretation can be affected by prior surgery, fractures or changes such as spinal arthritis. A clinician may exclude an unsuitable measurement instead of treating every printed number as equally reliable (MedlinePlus).
Tell the person interpreting the scan about earlier fractures or surgery. If your report contains a note about an excluded vertebra or artifact, ask how that affects the conclusion. A diagnosis should not be reconstructed from a screenshot of one number without the rest of the report.
Does a small change mean treatment failed?
A change between scans must be large enough to exceed the testing facility's measurement error before it can confidently be called real. ISCD uses a facility-specific threshold abbreviated LSC for this comparison. Comparisons across machines require suitable cross-calibration; the timing of a repeat scan should have a defined clinical purpose (ISCD).
Keep the complete previous report, the date and the facility name. Ask whether the current comparison used the same site and a comparable scanner. If the difference is within measurement uncertainty, a new decimal place is not a sound reason to change treatment yourself.
NIAMS advises reviewing the result with your doctor because treatment takes account of age and other fracture risks as well as density. Ask what the scan changes in your plan: medicines, fall prevention, exercise or the date of a future test (NIAMS). If new pain follows a fall or you suspect a fracture, seek clinical assessment rather than waiting for the next screening scan.
Frequently asked questions
Is a T-score a percentage of bone lost?
No. It compares bone density with a young-adult reference in standard-deviation units. It is not a percentage.
Can I compare numbers from different scanning centers?
Not reliably without knowing whether the systems were cross-calibrated. Ask the clinician interpreting the reports before treating a small difference as real bone loss.
References
- Official Adult Positions 2023 · International Society for Clinical Densitometry
- Bone Mineral Density Tests: What the Numbers Mean · NIH NIAMS
- Bone Density Scan · MedlinePlus