What Does a DEXA Scan Show — and What It Misses

What does a DEXA scan actually show?

A DEXA scan shows how dense your bones are — measured with low-dose X-rays, usually at the spine and hip, and reported as a T-score and Z-score. DEXA (also written DXA, short for dual-energy X-ray absorptiometry) is the standard test the NHS uses to diagnose osteoporosis or assess your risk of it, alongside a fracture-risk assessment NHS, 2024.

The logic is straightforward: denser bones are generally stronger and less likely to break, so measuring bone mineral density gives clinicians a reliable, standardised number to work with. The scan is quick, painless and uses only a very low dose of radiation. It typically focuses on the lumbar spine and hip — the two sites where fractures cause the most harm — and sometimes the forearm or wrist Royal Osteoporosis Society, 2024.

If you want the deeper mechanics of what a bone scan involves, our guide to what a bone health assessment covers walks through it step by step.

What do the T-score and Z-score mean?

Your DEXA result comes as two numbers: a T-score, which compares your bone density to a healthy young adult, and a Z-score, which compares it to people your own age. The T-score is the one used to make a diagnosis.

According to the Royal Osteoporosis Society, the T-score thresholds are:

• +1 to −1 — normal bone density.
• −1 to −2.5 — low bone density, known as osteopenia.
• −2.5 or below — within the osteoporosis range.

The Z-score sits alongside this to flag when bone loss is unusual for your age — useful for spotting a cause beyond ordinary ageing Royal Osteoporosis Society, 2024. Importantly, these numbers are read alongside a fracture-risk assessment, not in isolation — the score is one input, not the whole verdict NHS, 2024.

Can a DEXA scan measure body fat or body composition?

Some DEXA machines can — but the scan used to diagnose osteoporosis is not measuring your body fat. Whole-body DEXA densitometry can produce a highly accurate breakdown of fat mass, lean (muscle) mass and bone mineral content, including region by region across the trunk, arms and legs, and as a percentage body fat Radiologia Brasileira, 2022. That's why you may have seen DEXA offered in sports clinics and body-composition studios.

This is a common point of confusion, so it's worth being precise: body-composition scanning depends on the machine and protocol, and it is a different job from the axial spine-and-hip scan used for osteoporosis. For clarity, the REMS scan used by Screen My Bones is bone-only — it estimates bone density and quality, and does not measure body fat or body composition.

What does a DEXA scan miss?

DEXA measures bone density, but not bone quality — the internal 3D microarchitecture that also determines how strong a bone is. This is the single most important thing to understand about the test.

A 2023 review in the Indian Journal of Orthopaedics puts it plainly: DEXA measures areal, two-dimensional density (in g/cm²) and "does not convey information regarding the 3D microstructure and architecture of bone as well as cortical porosity" Indian Journal of Orthopaedics, 2023. The same review notes that single-site measurement can leave a meaningful share of osteoporosis cases undetected — one reason a "normal" number on a single site isn't a full clean bill of health.

The Royal Osteoporosis Society is refreshingly honest about this too, stating outright that DEXA results "do not give a complete picture of your bone strength" Royal Osteoporosis Society, 2024.

Can you break a bone even if your DEXA result is normal?

Yes — and it's more common than most people expect. Because density and quality aren't the same thing, a normal or borderline DEXA does not fully rule out fracture risk.

The clearest illustration comes from a large population study by Pasco and colleagues, where 73.1% of fragility fractures occurred in women who did not have osteoporosis on their scan — 56.5% had osteopenia and 16.6% had entirely normal bone density Osteoporosis International, 2006. The authors concluded that the population burden of fractures arises mainly in women with osteopenia, not osteoporosis. (This was an Australian cohort, so treat the exact figure as illustrative of the density-versus-fracture gap rather than a UK-specific number.)

The practical message: a good T-score is reassuring, but it isn't a guarantee. Bone quality is doing work that a density scan simply can't see.

What can assess the bone quality that DEXA misses?

Bone quality needs a different measurement — and REMS is a radiation-free ultrasound method built to add exactly that. REMS (Radiofrequency Echographic Multi Spectrometry) is a portable, radiation-free tool that estimates bone mineral density, T-score and Z-score at the lumbar spine and femur — the same sites DEXA uses — and then adds a Fragility Score that reflects bone microarchitecture independently of density, on a scale from 0 (normal) to 100 (maximum fragility) Diagnostics, 2025.

In a 2025 systematic review, REMS showed diagnostic concordance with DXA of 88.8% at the lumbar spine and 88.2% at the femoral neck, and the lumbar Fragility Score reached an AUC of 0.811 for identifying people with fragility fractures — outperforming both REMS density and the DXA T-score in that analysis Diagnostics, 2025. It's worth being measured here: these figures come from selected research cohorts, not head-to-head UK screening trials, and REMS is not a replacement for DXA in formal diagnosis. But as a way to add the bone-quality picture DEXA can't provide — without ionising radiation — the published evidence is genuinely promising. We compare the two side by side in REMS vs DEXA, and you can read how the technology works on our REMS bone density scan page.

DEXA vs REMS: what each one shows

Here's the short version. DEXA is the established, NHS-standard density test — excellent at what it does, but blind to bone quality. REMS adds that missing quality dimension, radiation-free.

• DEXA shows: bone mineral density at spine and hip (sometimes forearm), T-score and Z-score; some whole-body machines also do body composition.
• DEXA misses: 3D microarchitecture and bone quality — which is why some people fracture at "normal" density.
• REMS adds: an estimate of density plus a Fragility Score for bone quality, at the spine and femur, with no ionising radiation.

As a rough guide to cost, a private DEXA scan in the UK is offered from around £145 at some standalone clinics as of 2026 — for example Vista Health — though prices vary by provider and whether a consultation is included, so treat any single figure as a starting point rather than a fixed rate Vista Health, 2026.

If you'd rather have both the density number and the bone-quality picture in one radiation-free appointment, you can book a Screen My Bones assessment day near you.

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This article is part of our screening technology series.