A bone density test can help identify osteoporosis before a fracture happens. It can also guide treatment decisions and help your clinician assess changes over time.
The most commonly used test is dual-energy X-ray absorptiometry, usually called DXA or DEXA. However, understanding your results involves more than reading a single score.
Your age, fracture history, medicines, and other health conditions help determine what the findings mean for you.
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Exploring a commercial osteoporosis program? You can review this program’s information, including its claims and purchase terms. A program cannot replace diagnostic testing or interpretation by a qualified clinician.
What Does a Bone Density Test Measure?
A bone mineral density test measures the amount of mineral in a defined area of bone. Central DXA usually examines the hip and lower spine.
The results help clinicians:
- Identify low bone density or osteoporosis.
- Estimate fracture risk alongside other information.
- Establish a baseline for future comparisons.
- Monitor the response to treatment.
A scan does not directly measure every aspect of bone strength. It also cannot, by itself, explain why bone loss happened.
If you are unfamiliar with the condition, start with our guide to understanding osteoporosis.
Who Should Have a Bone Density Test?
Testing recommendations depend on your circumstances and the guidelines used in your country.
In the United States, the USPSTF recommends screening:
- Women aged 65 or older.
- Postmenopausal women younger than 65 who have an increased fracture risk, identified through clinical assessment.
For men, the USPSTF concludes that evidence is insufficient to determine the overall benefits and harms of routine screening. This does not mean men should never be tested. BHOF recommends discussing testing for men aged 70 or older and younger men with relevant risk factors.
Testing may also be appropriate following a fracture after minor trauma, or when a medical condition or medicine increases bone-loss risk.
These situations involve individualized assessment rather than simply waiting to reach a screening age. Tell your clinician about previous fractures and long-term steroid use.
Your clinician may also use a FRAX fracture-risk assessment to interpret your bone-density results alongside other risk factors.
DXA and Other Bone Tests: What Is the Difference?
Different tests answer different questions.
| Test | Main role | Important limitation |
|---|---|---|
| Central DXA | Measures hip and spine density; commonly used for diagnosis and monitoring | Results need clinical interpretation |
| Forearm DXA | Useful when certain circumstances make hip or spine assessment unsuitable | The correct measurement site matters |
| Quantitative CT, or QCT | Measures bone density using CT-based methods | Requires specialized interpretation; results are not directly interchangeable with standard DXA |
| Heel ultrasound | Can help assess fracture risk in some settings | Does not replace central DXA for routine diagnosis or treatment monitoring |
| Vertebral fracture assessment, or VFA | Looks for vertebral fractures using lateral images obtained on a DXA machine | Answers a different question from the density measurement |
| Standard X-ray | Helps identify fractures and other structural problems | Is not the standard test for measuring early bone-density loss |
Ask what test is being offered before booking a “bone health check.” A heel screening at a community event is different from a clinical hip-and-spine DXA examination.
How to Prepare for a DXA Scan
Follow the testing centre’s instructions. Preparation commonly includes:
- Wearing comfortable clothing without metal around the areas being scanned.
- Avoiding calcium supplements for at least 24 hours beforehand.
- Informing staff if pregnancy is possible.
- Mentioning recent barium examinations, contrast scans, or nuclear medicine tests.
During the examination, you usually lie on an open table while the scanner passes over you. The procedure is generally painless and uses a small amount of radiation.
Bring previous scan reports if they were performed elsewhere.
Understanding Your T-Score
A T-score compares your bone density with a young-adult reference population.
For postmenopausal women and men aged 50 or older, the usual categories are:
| T-score | Classification |
|---|---|
| −1.0 or higher | Normal bone density |
| Below −1.0 but above −2.5 | Low bone density, often called osteopenia |
| −2.5 or lower | Osteoporosis |
A score of −2.5 does not mean that you have lost 25% of your bone.
The classification is only part of the assessment. Certain low-trauma fractures can establish osteoporosis even when the T-score is above −2.5.
What about Z-scores?
Z-scores compare bone density with an age-matched reference population. They are generally preferred for premenopausal women and men younger than 50.
A Z-score of −2.0 or below is described as “below the expected range for age.” It needs clinical evaluation; it does not automatically establish osteoporosis on its own.
Considering extra support after your results? Read about this commercial osteoporosis program and discuss any proposed treatment changes with your clinician. A scan result alone cannot show that a particular program will work for you.
How Accurate Are Bone Density Scans?
DXA is an established clinical test, but careful technique and interpretation matter.
Positioning, analysis choices, spinal arthritis, and other structural changes can affect the findings. An unexpectedly high spine result does not always mean that those bones are stronger.
For repeat scans, the key question is whether a difference represents a real change.
Small changes may be measurement variation
Each testing facility should determine its least significant change, or LSC. This is the threshold used to judge whether a measured difference exceeds expected testing variation.
For example, a small reported increase should not automatically be described as successful bone rebuilding.
Whenever possible, return to the same facility and machine. If equipment changes, appropriate cross-calibration may be needed for valid numerical comparisons.
Ask:
“Was the change in my bone density large enough to be considered significant?”
How Often Should You Repeat the Test?
There is no single schedule for everyone.
BHOF advises that testing is often repeated one to two years after starting or changing osteoporosis treatment. Later intervals depend on your clinical circumstances.
Someone with stable results may need a different schedule from someone taking a medicine associated with rapid bone loss.
Repeated testing should help answer a useful question, such as whether the findings would change treatment. Testing every few months generally cannot provide a meaningful picture of routine progress.
Keep a record of:
- Scan dates and testing locations.
- The bones measured.
- Bone-density values and scores.
- Treatment start dates or changes.
- Any fractures since the previous appointment.
Can You Monitor Bone Density at Home?
Consumer smart scales, watches, and phone apps should not be treated as substitutes for clinical bone-density testing.
A scale displaying “bone mass” does not provide the same measurement as a hip-and-spine DXA scan.
Home records can still support your care. Track falls, medication use, and questions for your next appointment. Share new symptoms with your clinician rather than using an app to decide whether your bones have improved.
What Should You Do After Receiving Your Results?
Ask your clinician to explain the findings in the context of your overall fracture risk.
Useful questions include:
- Do these results establish osteoporosis?
- Does my fracture history change the interpretation?
- Do I need assessment for a contributing medical condition?
- Would treatment reduce my fracture risk?
- When should I be tested again?
Your next steps may include nutrition changes, an appropriate exercise program, and a discussion of osteoporosis treatment options.
A better score is encouraging, but it should be interpreted alongside your treatment history. Our guide to whether osteoporosis can be reversed explains this distinction.
Before buying additional guidance: You can check this osteoporosis program’s details. Compare its recommendations with your clinician’s plan and avoid promises of guaranteed scan improvements.
References and Further Reading
- NIAMS: Bone Mineral Density Tests—What the Numbers Mean
- BHOF: Bone Density Testing
- USPSTF: Osteoporosis Screening Recommendations
- ISCD: Official Adult Positions
- RadiologyInfo: Bone Density Scan
Medical disclaimer: This article provides general education and does not replace individualized medical advice, diagnosis, or treatment.
Affiliate notice: Commercial links do not establish that a program diagnoses or treats osteoporosis.