A DEXA scan is one of the standard ways to measure bone density and assess bone strength. It is often used when doctors want to know whether your bones have become thinner or weaker than expected, especially before a fracture occurs.
Because the scan is quick, painless, and low dose, it is a practical way to screen for osteoporosis and monitor bone health over time.
Why might my doctor request a DEXA scan?
Your doctor may request a DEXA scan to:
- Check for osteopenia or osteoporosis
- Evaluate fracture risk
- Follow known low bone density over time
- Monitor the effect of osteoporosis treatment
- Assess bone health in people with risk factors such as age, menopause, steroid use, or certain chronic illnesses
What exactly does a DEXA scan measure?
A DEXA scan measures bone mineral density. In simple terms, it helps show how much mineral is packed into your bones and gives doctors an estimate of how strong those bones are.
The scan does not diagnose every possible bone problem, but it is very useful for identifying thinning bones and fracture risk.
Which parts of the body are scanned?
Most standard DEXA scans assess:
- The lower spine
- One or both hips
Sometimes the forearm is assessed if the usual sites cannot be measured properly or if there is a specific clinical reason.
What happens during the scan?
During the test:
- You lie on a padded table
- The Radiographer positions you carefully
- A scanning arm passes over the part of the body being assessed
- You stay still while the machine takes measurements
The scan is open and does not involve a tunnel like MRI. Most people find it very easy to tolerate.
Do I need to prepare before the test?
Preparation is usually minimal.
Your imaging center may ask you to:
- Avoid calcium supplements for a period before the exam, often 24 hours
- Wear clothes without metal zips, belts, or buttons around the scan area
- Inform the team if you recently had a barium study or a contrast/tracer-based imaging test
- Mention possible pregnancy before the scan
Can I eat or drink before a DEXA scan?
Yes, in most cases you can eat and drink normally before the scan unless your center gives different instructions.
Will the scan hurt?
No. A DEXA scan is painless and noninvasive. There are no injections and no special recovery time afterward.
How long does a DEXA scan take?
The imaging itself is usually quick, often around 10 to 20 minutes. The full visit may take a little longer depending on check-in and positioning.
Is DEXA safe?
For most people, yes. It uses a very low dose of radiation and is generally considered a safe test when medically indicated.
Even though the dose is low, it is still an X-ray-based examination, so pregnancy should always be mentioned before the scan.
Can children have a DEXA scan?
Yes, when medically needed. In children and adolescents, DEXA may be used in selected cases to assess bone health, but interpretation is different from that in adults. Pediatric results need to be read in the right age and growth context.
What do T-scores and Z-scores mean?
These are ways of interpreting the result:
- A T-score compares your bone density with that of a healthy young adult and is commonly used in adults for osteoporosis assessment.
- A Z-score compares your bone density with others of a similar age or stage of life and may be more helpful in some patients, especially younger people.
Your doctor will explain which score applies to you and what the result means in practical terms.
When will I get my results?
A radiologist or another qualified clinician reviews the study and reports the bone density results. Your doctor will then explain whether your bones are within the expected range, mildly low, or in a range suggesting osteoporosis.
What are the important limitations?
DXA measures two-dimensional areal bone mineral density; it does not measure every aspect of bone strength. Arthritis, vertebral compression, calcification, previous surgery, metalwork, positioning, and differences between machines can distort results. Fracture risk must combine the usable DXA sites with age, previous fractures, medicines, falls, medical conditions, and—when appropriate—a validated risk tool.
A fragility fracture can justify an osteoporosis diagnosis or treatment assessment even when the T-score is not in the osteoporosis range. For monitoring, compare valid studies from the same facility and machine where possible, and only call a change real when it exceeds that facility's least significant change (LSC). The timing of another scan should be individualised.
Sources and further reading
- International Society for Clinical Densitometry: 2023 Adult Official Positions
- RadiologyInfo.org: Bone density scan (DXA)
Conclusion
A DEXA scan is a simple but very useful test for measuring bone density and estimating fracture risk. It is low dose, painless, and easy to tolerate, and it plays a major role in screening for osteoporosis and monitoring long-term bone health.