Bone density test results: reading your DEXA report

What is on the report

The ISCD says a DXA report should include: the machine used, the sites scanned (and which side), your bone mineral density (BMD) in g/cm² for each site, the T-score or Z-score as appropriate, a diagnostic category, the fracture risk tool used and which risk factors went into it, and when a next scan is advised. (ISCD, 2023) A higher score means denser bone; the lower the score, the higher the fracture risk. (MedlinePlus, 2024)

Which site counts

Spine and hip are both measured in everyone. (ISCD, 2023)
The lowest counts: osteoporosis can be diagnosed if the T-score of the lumbar spine, total hip or femoral neck is -2.5 or lower. For the hip, use the femoral neck or total hip, whichever is lower; if both hips were scanned, the lowest one counts, not the average. (ISCD, 2023)
Spine (L1 to L4): a vertebra can be left out if it is affected by a structural change or artifact, for example if it differs from its neighbors by more than 1.0 T-score. The rest are used. A single vertebra is not used for a diagnosis. (ISCD, 2023)
Forearm (33% radius): used when the hip or spine cannot be measured or read, in hyperparathyroidism, or when a person is over the weight limit of the DXA table. (ISCD, 2023)
Not used for diagnosis: other hip areas such as Ward's area and the greater trochanter. (ISCD, 2023)

For what each T-score range means (normal, low bone mass, osteoporosis), see the table on bone density test: how often to repeat it. The ISCD prefers the words "low bone mass" or "low bone density" to "osteopenia", and notes that people with low bone mass are not necessarily at high fracture risk. (ISCD, 2023)

T-score or Z-score

Women after menopause and men 50 and older: T-scores are preferred and the WHO categories apply. They can also be applied to women in the menopausal transition. (ISCD, 2023)
Women before menopause and men younger than 50: Z-scores are preferred. A Z-score of -2.0 or lower is "below the expected range for age"; above -2.0 is "within the expected range for age". Bone density alone does not diagnose osteoporosis in these groups. (ISCD, 2023) (BHOF, 2022)

Where bodies differ: the T-score reference is the same for everyone. The ISCD uses a database of white women aged 20 to 29 for femoral neck and total hip T-scores, and BHOF notes this applies to women and men of all ethnic groups. Z-scores, by contrast, may use reference data matched to your self-reported ethnicity where good data exist. (ISCD, 2023) (BHOF, 2022)

What FRAX adds

The USPSTF notes that most fragility fractures happen in people whose T-score is above -2.5, which is why fracture risk is also assessed. (USPSTF, 2025) FRAX estimates your 10-year chance of a hip fracture and of a major osteoporotic fracture (spine, hip, forearm or upper arm), for adults 40 to 90. (BHOF, 2022) The USPSTF says FRAX alone and bone density alone predict about equally well, and both are less accurate than FRAX plus bone density. (USPSTF, 2025)

Which number goes in: BHOF prefers femoral neck BMD in g/cm², not the T-score, and says FRAX is not validated for spine BMD. If your spine score is low but your hip is fairly normal, FRAX underestimates your risk. (BHOF, 2022)
What it leaves out: falls, frailty, spine bone density, and doses of steroids or alcohol (FRAX only asks yes or no). (USPSTF, 2025) (BHOF, 2022)
Trabecular bone score (TBS): some newer machines add a TBS from the spine image to adjust FRAX. The ISCD says TBS should not be used alone. (ISCD, 2023) (BHOF, 2022)

Where they differ: the US version of FRAX asks you to choose one of four ethnicities, and BHOF says it helps sort fracture risk. The USPSTF says there are concerns about race-specific calculators: they always give lower risk for Asian, Black and Hispanic people than for white people with the same age, bone density and risk factors, and it is unclear which version fits people who are multiracial. (BHOF, 2022) (USPSTF, 2025) The USPSTF also says there is no defined FRAX threshold for screening. (USPSTF, 2025) How your FRAX result fits with your T-score is a conversation with your doctor.

Comparing with an earlier scan

Bone density changes slowly, and every scan has some error. BHOF says changes of less than 3 to 6% at the hip and 2 to 4% at the spine may be due to the test itself. (BHOF, 2022) Each DXA center works out its own least significant change (LSC), and a follow-up report should say which earlier scan it compares with, state the LSC, and report any significant change in g/cm² and percent. (ISCD, 2023)

Go back to the same machine when you can. Scans from two machines can only be compared if they were cross-calibrated; if not, the new scan becomes a new baseline. (ISCD, 2023) How often to repeat the scan: see bone density test: how often.

Questions people ask

Which T-score counts on my bone density report?

The lowest one of the lumbar spine (L1 to L4), the total hip and the femoral neck. For the hip, the ISCD says to use the femoral neck or total hip, whichever is lower. Other hip areas, such as Ward's area, are not used for diagnosis. (ISCD, 2023)

Why does my report show a Z-score instead of a T-score?

For women before menopause and men younger than 50, the ISCD prefers Z-scores, which compare you with people of your own age. A Z-score of -2.0 or lower is called "below the expected range for age". In these groups, bone density alone does not diagnose osteoporosis. (ISCD, 2023) (BHOF, 2022)

What is FRAX on a bone density report?

FRAX estimates your 10-year chance of a hip fracture and of a major osteoporotic fracture (spine, hip, forearm or upper arm). It is meant for adults 40 to 90 and uses your risk factors plus, ideally, your femoral neck bone density. The USPSTF says FRAX plus bone density predicts better than either alone. (BHOF, 2022) (USPSTF, 2025)

My bone density went down a little. Is that real?

Maybe not. Every machine has some measurement error. BHOF says changes of less than 3 to 6% at the hip and 2 to 4% at the spine may be due to the test itself. Each center works out its least significant change (LSC), and a follow-up report should say whether your change is larger than that. (BHOF, 2022) (ISCD, 2023)

Does it matter which machine I use for a repeat scan?

Yes. The ISCD says to go back to the same DXA machine when possible. Numbers from two machines can only be compared if they have been cross-calibrated; otherwise the new scan becomes a new baseline. (ISCD, 2023)