Compared
DEXA scan vs X-ray for osteoporosis
A DEXA scan measures bone mineral density at the hip and spine using a very low X-ray dose and is the standard test for diagnosing osteoporosis and low bone mass. A plain X-ray is poor at measuring density, since bone must be substantially lost before it looks thin, but it is the test for finding fractures, including silent spinal fractures. They answer different questions.
Last checked: 2026-10-03
Key facts
At a glance.
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Density
DEXA gives a measured bone mineral density and a T-score; X-ray cannot reliably measure density.
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Fractures
X-ray (or sometimes CT or vertebral imaging on a DEXA machine) shows broken bones, including spinal compression fractures.
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Dose
DEXA uses a very low radiation dose, much lower than most standard X-rays and CT.
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Risk assessment
NICE recommends assessing fracture risk with tools such as FRAX or QFracture, and using DEXA where it will help decide on treatment.
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Speed
A DEXA scan typically takes 10 to 20 minutes with no preparation beyond avoiding calcium tablets on the day.
What osteoporosis testing is trying to answer
Osteoporosis is a condition of low bone strength that raises the risk of fracture. Testing aims to find out two things: how dense the bones are, and whether fractures have already occurred. These are different questions, which is why different tests are used.
A DEXA scan answers the first question. An X-ray answers the second. Someone with a previous low-trauma fracture, for example a wrist or spine fracture from a fall from standing height, may have a diagnosis made on clinical grounds even before density is measured.
Why X-rays cannot measure bone density well
On a standard X-ray, bones appear thin or "ghostly" only after a substantial proportion of mineral has been lost. By then osteoporosis is often advanced. The picture is also affected by exposure settings and body size, so it is not a reliable measuring tool.
X-rays remain essential in osteoporosis care for another reason: they show fractures, including compression fractures of the spine that can happen without a clear injury and may be found incidentally or because of height loss and back pain.
What a DEXA scan gives you
DEXA (dual-energy X-ray absorptiometry) uses two low-dose X-ray beams to estimate mineral content, usually at the lumbar spine and hip. The results are reported as a T-score, comparing you to a healthy young adult, with osteoporosis defined by a score at or below minus 2.5. Some units also offer vertebral fracture assessment during the same visit.
DEXA can be unreliable if the spine has severe arthritis, previous surgery or a fracture, since these add apparent density, and the hip result may then be more reliable. The test also does not capture bone quality directly.
Compared
| Feature | DEXA scan | Plain X-ray |
|---|---|---|
| Main purpose | Measure bone density; diagnose osteoporosis | Show fractures and deformity |
| Detects early bone loss | Yes | No |
| Detects spinal fracture | Possible with vertebral assessment | Yes |
| Radiation | Very low | Low to moderate |
| Time | Short | Short |
| Used to monitor treatment | Yes, at intervals | No |
| Limitations | Affected by arthritis and metal in the spine | Insensitive until substantial bone is lost |
What clinicians usually decide and why
NICE guidance on osteoporosis assessment (CG146) recommends assessing fracture risk in women aged 65 and over and men aged 75 and over, and in younger people with risk factors, using a risk tool, and offering DEXA where the result could change the treatment decision. The principle is to use bone density as one input rather than testing everyone.
When someone presents with a suspected fracture, X-ray is the first test. Where osteoporosis is suspected, DEXA follows, along with blood tests to look for treatable contributors such as vitamin D deficiency or thyroid problems.
How to decide
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You broke a bone after a minor fall: X-ray for the fracture, then discuss fracture risk and DEXA with your GP.
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Early menopause, long-term steroid use, a family history of hip fracture, or low body weight: ask about fracture risk assessment and whether DEXA is appropriate.
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Height loss or new upper back pain: X-ray or spine imaging for a compression fracture.
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Already on osteoporosis treatment: DEXA at intervals advised by your clinician to monitor.
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No risk factors: routine DEXA is not generally recommended.
Common misconceptions
A normal X-ray does not exclude osteoporosis, and a DEXA scan does not show whether a fracture has occurred. Another misconception is that osteoporosis only affects older women; men and younger people with risk factors can be affected.
Equally, a low T-score does not mean a fracture is inevitable. Treatment decisions combine the score with age, history and other risk factors.
Frequently asked
Questions people ask.
Quick, plain-English answers to the questions we hear most.
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Can an X-ray show osteoporosis?
Only when it is advanced. It is not reliable for diagnosis; DEXA is the standard test.
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Is DEXA radiation harmful?
The dose is very low, much lower than most X-rays or CT scans, and it is considered justified when it will guide treatment.
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What does a T-score of minus 2.5 mean?
It is the threshold at which bone density is classed as osteoporosis in the WHO definition. Your clinician interprets it with your overall risk.
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Do I need to prepare for a DEXA scan?
Usually you avoid calcium supplements on the day and wear clothing without metal. Follow the booking instructions.
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How often should DEXA be repeated?
It depends on risk and treatment. Intervals of a few years are common; your clinician will advise.
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Can DEXA detect spinal fractures?
Some machines can perform vertebral fracture assessment, but X-ray remains the standard for confirming fractures.
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Who should be tested?
People at higher risk, based on assessment with a fracture risk tool, rather than everyone.
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Is a private DEXA scan worthwhile?
It can be if there is a clinical reason, but results should be reviewed by someone who can assess your overall fracture risk.
Where this comes from
Sources and checking.
This guide is for information, not medical advice.
Your GP or consultant knows your history and can tell you which parts apply to you. If your symptoms are severe, rapidly worsening, or come with red-flag features, seek urgent medical care. Figures and availability change, so treat them as a guide and confirm with the provider.
Published 2026-10-03, next review 2027-10-03.
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NHS website (nhs.uk) patient information pages on the tests and procedures discussed, consulted October 2026
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NICE clinical guideline CG146: Osteoporosis, assessing the risk of fragility fracture (nice.org.uk/guidance/cg146), consulted October 2026
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Royal Osteoporosis Society patient information on bone density scans (theros.org.uk), consulted October 2026