DEXA scan results describe your bone mineral density, usually at the hip and lower spine. The T-score compares it with a young-adult reference, while the Z-score compares it with an age-matched reference. Your clinician combines those measurements with your fracture history and other risk factors before deciding what to do next.
Key takeaways
- A T-score is not a percentage. A result of −2.0 does not mean you have lost 20% of your bone.
- Different scan sites can give different results. Hip and spine measurements need to be assessed for quality and clinical relevance.
- The scan is one part of fracture-risk assessment. A result above the osteoporosis threshold does not rule out an important fracture risk.
- A small change is not automatically meaningful. Comparisons should consider measurement variation and whether the scans are technically comparable.
- Ask for a plan as well as a score. Understand whether you need further investigation, treatment or follow-up.
A bone density report can contain several tables, percentages, coloured charts and unfamiliar abbreviations. It is understandable to focus on the lowest number. A better approach is to work through what was measured, which reference was used and how the findings relate to your health.
What does a DEXA report measure?
DEXA, also written DXA, stands for dual-energy X-ray absorptiometry. It uses low-dose X-rays to estimate bone mineral density (BMD). A diagnostic scan commonly measures the lumbar spine and hip. Some people also have a forearm measurement when this is clinically appropriate.
The report may show BMD in grams per square centimetre, a T-score and a Z-score for each measured region. At the hip, “femoral neck” means a particular part near the top of the thigh bone; “total hip” refers to a larger measurement region. These are different measurements, not alternative names for one number.
A standard BMD measurement does not directly measure every aspect of bone quality, diagnose every cause of pain or establish whether you have a spinal fracture. Additional imaging, such as vertebral fracture assessment, may be considered when indicated. Our testing and diagnosis guide explains the complementary investigations.
What does your T-score mean?
The T-score expresses how far your bone density differs from a young-adult reference, measured in standard deviations. A negative score is below that reference average; a positive score is above it. It is not the percentage of bone you have lost.
The following categories are generally used to interpret suitable central DEXA measurements in postmenopausal women and men aged 50 and over:
| T-score | Bone-density category | What it means |
|---|---|---|
| −1.0 or higher | Normal range | Within the usual young-adult reference range; other fracture risks can still matter. |
| Below −1.0 and above −2.5 | Low bone density (osteopenia) | Lower bone density, with next steps guided by the overall clinical assessment. |
| −2.5 or lower | Osteoporosis range | A result that can support a diagnosis of osteoporosis at an appropriate, valid measurement site. |
For example, −1.8 is in the osteopenia range, while −2.5 is already in the osteoporosis range. The cut-off includes −2.5; it is not restricted to numbers lower than that. The categories should not be applied to children or younger adults without the appropriate clinical interpretation.
How is a Z-score different?
A Z-score compares your bone density with an age-matched reference rather than a young-adult reference. It can be particularly useful when assessing a younger adult or investigating whether a result is unexpectedly low for someone’s age.
A low Z-score may prompt further questions about an underlying condition, medication or another contributor to bone loss. It does not identify the cause by itself. Equally, an age-appropriate Z-score does not mean that an older person has no fracture risk: bone density and fracture risk are different parts of the assessment.
Why can the hip and spine results disagree?
Bone density is not identical throughout the skeleton, so a difference between sites is common. The lumbar spine and hip contain different proportions of bone types and can be affected differently by ageing, illness and treatment.
Technical and anatomical factors also matter. For example, degenerative changes in the spine can make its measured density appear higher. Previous surgery, a fracture or another local feature may affect which measurements can be interpreted. NOGG guidance specifically highlights the influence of degenerative spinal changes on BMD.
Do not average the T-scores yourself or assume that the most reassuring reading cancels out the lowest one. Your clinician should check the report and scan quality, identify the valid measurement sites and explain which results inform diagnosis and management.
Does a low score mean you will break a bone?
No. Lower bone density is an important risk factor, but it cannot predict an individual fracture with certainty. Age, previous fractures, medicines, falls and other health factors also contribute. Some people fracture with a T-score above −2.5, while others with a lower score do not.
For appropriate adults, FRAX estimates the ten-year probability of a hip fracture and a major osteoporotic fracture, using clinical information with or without a femoral-neck BMD measurement. A clinician then interprets that estimate, including relevant factors it may not fully capture. It is not interchangeable with the T-score.
This is why a scan can lead to different plans for people with similar numbers. One person may be advised on nutrition, exercise and reassessment; another may be offered medication because their overall risk is higher. See our overview of osteoporosis treatment options.
Has your bone density changed since the last scan?
If you have had more than one DEXA scan, look for the report’s comparison with your previous BMD measurements. Ask whether the same sites and a comparable scanning method were used. Where possible, follow-up at the same centre and on the same machine makes comparison easier.
Every measurement has some variation. A small numerical difference may not represent a true gain or loss. Your clinician or scanning service can explain whether the change exceeds the variation expected from that equipment and measurement process.
A stable result can be useful, particularly when the aim is to prevent further loss. Changes in treatment should also take account of fractures, treatment adherence, side effects and overall risk. The number on a repeat report should not be the sole reason to stop or switch a prescribed medicine.
What should happen after you receive the results?
A useful results discussion should answer four questions:
- Are the measurements valid and complete? Confirm which sites were scanned and whether anything affected interpretation.
- What do they mean for my fracture risk? Discuss previous fractures, medicines, family history and falls as well as the score.
- Is any further investigation needed? Blood tests or additional imaging may be appropriate in particular circumstances.
- What is the plan? Agree on any treatment, nutrition or exercise support, and the reason for the follow-up interval.
Bring the full report, previous scan reports, a current medication list and details of any fractures. There is no universal requirement to repeat DEXA every year: the interval should reflect your circumstances and whether another measurement is likely to change management.
New persistent back pain, a suspected fracture or unexplained height loss should be assessed clinically rather than waiting for a scheduled repeat scan.
Frequently asked questions
Is a T-score of −2.5 osteopenia or osteoporosis?
It is in the osteoporosis range when the T-score categories are appropriate for the person and the measurement is taken at a valid diagnostic site. Osteopenia is below −1.0 but above −2.5.
Does a T-score of −2 mean I have lost 20% of my bone?
No. T-scores are expressed in standard deviations from a reference, not percentages. A report may show percentage comparisons separately, but those are different measures.
Can I have osteoporosis at the spine but osteopenia at the hip?
Yes, measurements at different sites can fall into different ranges. Your clinician should review the validity of each result and explain how the findings affect the diagnosis and treatment plan.
Do normal DEXA results rule out a fracture?
No. A standard bone-density measurement is not a test for every fracture or cause of pain. Symptoms and injury history may require separate examination and imaging, even when BMD is in the normal range.
Do I need to repeat a scan done at another clinic?
Not automatically. Bring the existing report so your clinician can assess whether it provides the information needed. If a future comparison is required, they can advise on using the same centre or a suitably comparable measurement.
Discuss your scan with a bone-health specialist
London Osteoporosis Clinic can assess your bone health and review your results in the context of your medical history. An initial consultation with Dr Mahmud costs £400 and usually lasts 30 minutes. Imaging is charged separately unless included in a specified package.
Arrange a consultant assessment, read about our DEXA assessment and scanning pathway in London, or check the current fees.
This article provides general information. A clinician who knows your medical history should interpret your scan and advise on any treatment.
References and further reading
- NHS. Bone density scan: how it is performed and understanding your results.
- Royal Osteoporosis Society. Bone density scan (DEXA/DXA).
- National Osteoporosis Guideline Group. Introduction to osteoporosis and fragility fractures.
- National Osteoporosis Guideline Group. Fracture risk assessment and case finding.
- National Osteoporosis Guideline Group. Intervention thresholds and strategy.
