DEXA Bone Density Test: A Complete Guide
DEXA Bone Density Test: A Complete Guide (2025)
A DEXA bone density test is the clinical standard for measuring bone health and assessing osteoporosis risk. In this guide, we'll walk you through how the test works, who it's for, how to prepare, and what your results mean for your health—including safety and cost basics.
Note: BodySpec offers a full‑body DXA for body composition that also provides a whole‑body bone density snapshot. However, it is not a physician‑ordered diagnostic DXA of the hip/spine used to diagnose osteoporosis. For details on BodySpec's scan, see our overview: BodySpec DEXA body scan: procedure, cost, and booking.
At a glance: answers to the most common questions
- What is it? The standard test that measures bone mineral density (BMD) at the hip and spine to help diagnose osteoporosis and estimate fracture risk, as explained by RadiologyInfo's patient guide and the Mayo Clinic.
- Who needs it? Most women at age 65+ (earlier if risk factors are present). For men, evidence is insufficient for routine screening; clinicians individualize decisions based on risk, per the U.S. Preventive Services Task Force.
- How do I prepare? Wear comfy clothes without metal, skip calcium supplements for 24 hours, and mention if you're pregnant or recently had contrast/barium imaging—standard advice from RadiologyInfo.
- How long does it take? About 10–30 minutes and it's painless, according to the RadiologyInfo overview.
- Is it safe? Yes—the radiation dose is very low (typically <1 to ~15 µSv), similar to a day or two of natural background radiation, per the International Atomic Energy Agency and RadiologyInfo's radiation chart.
- How is it covered? Medicare Part B generally covers a bone density test every 24 months (more often if medically necessary) for those who qualify, per Medicare's coverage page.
- Where to schedule? For a diagnostic DXA of the hip/spine, ask your doctor about local imaging centers. To book a BodySpec full‑body DXA for body composition (not diagnostic), use our guide: Find a BodySpec DEXA scan near you.
What a diagnostic DEXA bone density test measures—and why it matters
A diagnostic DEXA (also called DXA) uses two very low‑dose X‑ray beams to measure how much mineral is packed into your bones at key sites—usually the hip and spine. Denser bones are generally stronger and less likely to break. Clinicians use this scan to diagnose osteopenia/osteoporosis, estimate fracture risk, and monitor treatment progress, as outlined by RadiologyInfo and the Mayo Clinic.
- Typical scan regions: lumbar spine and hip; forearm in select cases (see the official ISCD positions).
- Common reasons to test: screening at appropriate ages, prior low‑trauma fracture, long‑term steroid use, certain endocrine or GI conditions, or significant height loss (per the USPSTF and ISCD guidance).
Who should get screened—and when?
- Women 65+: screen all (per the USPSTF recommendation).
- Postmenopausal women <65 with risk factors (e.g., low body weight, parental hip fracture, smoking, excess alcohol, glucocorticoids): screen earlier (see the USPSTF guidance).
- Men: evidence is currently insufficient to recommend for or against routine screening; clinicians use judgment based on risk (per the USPSTF).
Want a deeper dive on timing? See our plain‑English explainer: When should women get a bone density test?
How to prepare (simple checklist)
- Clothing: Wear comfortable clothes without metal (avoid zippers, buttons, or underwires).
- Supplements: Skip calcium supplements for 24 hours beforehand.
- Recent imaging: Tell your provider if you recently had a barium study or other contrast imaging—you may need to wait.
- Pregnancy: Let your care team know if there's any chance you're pregnant.
These are standard patient prep steps from radiology societies such as RadiologyInfo and the Mayo Clinic.
What happens during the scan
You'll lie on a padded table while the scanner arm glides over your hip and/or spine. It's open (not a tunnel), quiet, and painless. Most exams take 10–30 minutes, and you may be asked to hold your breath briefly for a clear image, per RadiologyInfo and the CDC's fact sheet.
Understanding DEXA results: T‑score, Z‑score, and fracture risk
Your report includes two scores:
- T‑score: compares your bone density to a healthy young adult of the same sex.
- Z‑score: compares you to peers of the same age and sex.
Typical T‑score categories used in diagnosis are summarized by RadiologyInfo and the Mayo Clinic:
| T‑score | Category |
|---|---|
| ≥ −1.0 | Normal bone density |
| Between −1.0 and −2.5 | Osteopenia (low bone mass) |
| ≤ −2.5 | Osteoporosis |
A very low Z‑score (≤ −2.0) can suggest your bone density is below what's expected for your age and may prompt evaluation for secondary causes, per the official ISCD positions.
- Want help reading a DEXA report? Try our walkthrough: Interpreting DEXA scan results: T‑score, Z‑score, and body composition
- What is FRAX? It's an internationally validated calculator that estimates your 10‑year fracture risk based on age, sex, clinical risk factors, and (optionally) femoral neck BMD. Clinicians often use it alongside DEXA results to guide treatment decisions, as noted by the USPSTF. You can try the official FRAX® calculator, and see our step‑by‑step FRAX guide.
Advanced tools you might see on your report
- Vertebral Fracture Assessment (VFA): a very low‑dose lateral spine image on the DXA machine to detect vertebral fractures; indicated in patients with risk factors like height loss or long‑term glucocorticoids when T‑score < −1.0 (see the official ISCD positions).
- Trabecular Bone Score (TBS): analyzes spine image texture to estimate bone micro‑architecture and can adjust FRAX risk; useful near treatment thresholds (per the ISCD's guidance).
Radiation dose and safety: how "low" is low?
DXA uses a tiny dose of ionizing radiation. For a hip/spine exam, effective dose typically ranges from <1 to ~15 µSv—among the lowest in medical imaging, according to the IAEA. That's far below a standard chest X‑ray and similar to one or two days of natural background radiation, per RadiologyInfo's radiation dose chart.
Our guide to DEXA radiation: how much is it, and is it safe? offers a detailed look at the benefits and risks.
Types of DEXA scans vs. other bone tests
- Central (diagnostic) DXA of the hip and spine is the reference standard for diagnosing osteoporosis and monitoring therapy.
- In most cases, central DXA remains the preferred test for treatment decisions (per the official ISCD positions).
- Full‑body DXA measures whole‑body BMD and provides body composition (fat, lean mass, visceral fat). It's excellent for tracking body composition trends, but whole‑body BMD is not used to diagnose osteoporosis; diagnostic classification relies on hip/spine (and in select cases, forearm) sites (see the ISCD guidance and this overview in Quantitative Imaging in Medicine and Surgery).
- Peripheral DXA (pDXA) measures sites like the wrist or heel and can help screen risk, but it's less definitive for diagnosis and not preferred for monitoring treatment. Results from pDXA aren't interchangeable with central DXA (summarized by RadiologyInfo and the ISCD).
- QCT (Quantitative CT) and QUS (Quantitative Ultrasound) are different tests—not types of DXA:
- QCT can estimate bone density and even bone strength in some cases, but it uses a higher radiation dose than DXA and follows different reference standards.
- QUS (often at the heel) has no radiation and can help predict fracture risk, but it's not used to monitor treatment and is not interchangeable with DXA for diagnosis.
Costs and insurance basics (U.S.)
Medicare Part B generally covers bone mass measurement once every 24 months (more often if medically necessary) and you pay $0 when your provider accepts assignment, if you qualify (e.g., estrogen‑deficient and at risk, X‑ray shows possible vertebral fracture, long‑term steroids, primary hyperparathyroidism, or monitoring osteoporosis therapy), per Medicare. Commercial plans often follow similar rules but vary by policy.
- To arrange a diagnostic DXA of the hip/spine, talk with your clinician, who can refer you to a local imaging center.
How often to repeat a diagnostic DEXA
Follow‑up intervals depend on your baseline bone density, age, and whether you're on treatment. The USPSTF notes evidence is insufficient to define a one‑size‑fits‑all interval; many clinicians re‑scan every 1–2 years if you're on therapy, and less often if your bone density is normal and stable (see the USPSTF recommendation and ISCD guidance). Your clinician will personalize the plan.
How to support stronger bones (actionable steps)
- Incorporate a mix of strength training 2–3×/week and weight‑bearing exercises like walking, jogging, or stair climbing.
- Get enough calcium and vitamin D per your clinician's advice.
- Avoid tobacco; limit alcohol.
- Prevent falls: check vision, tidy home hazards, and practice balance exercises (for example, Tai Chi or standing on one leg).
For more on building and protecting bone, see the Bone Health & Osteoporosis Foundation's resources on nutrition for bone health and fracture‑prevention tips.
Our article on Strength training for bone density provides a practical training playbook.
BodySpec's role (and how it differs from a diagnostic DXA)
BodySpec offers full‑body DXA for body composition with a whole‑body bone‑density snapshot. It is effective for tracking fat, lean mass, and visceral fat—and for starting a bone‑health conversation—but it is not a physician‑ordered, diagnostic hip/spine exam used to diagnose osteoporosis.
Learn more in our guide to the BodySpec DEXA body scan, review performance data in our DEXA scan accuracy guide, and compare technologies in BodySpec DEXA vs other body composition tests.
If your BodySpec report suggests low bone density, bring it to your clinician to discuss a diagnostic DXA of the hip/spine and next steps.
Frequently asked questions
Is a DEXA bone density test painful?
No. You'll lie comfortably on a table; the test is quick and painless, per the RadiologyInfo patient overview.
Will I be exposed to a lot of radiation?
No. A hip/spine DXA is typically <1–~15 µSv—among the lowest in medical imaging, according to the IAEA.
Do I need to stop medicines before the test?
Don't change prescribed meds unless your clinician says so. Do avoid calcium supplements for 24 hours, and tell the technologist if you recently had a barium or contrast study (standard guidance from RadiologyInfo).
Can DXA predict fractures?
It can estimate risk—especially when combined with tools like FRAX. No test can guarantee who will fracture, but lower T‑scores generally mean higher risk (per the USPSTF).
How soon will I get results?
A radiologist interprets the images and sends a report to your clinician, who will share results and the plan (per RadiologyInfo).
The bottom line
A diagnostic DEXA bone density test is fast, painless, and highly informative. For most women, screening starts at 65—or earlier with risk factors. Your T‑score and Z‑score help your care team quantify bone strength and tailor treatment.
If you're ready to take action, check insurance coverage and talk with your clinician about a diagnostic DXA. If you want to benchmark body composition and get a whole‑body bone snapshot between clinical visits, a BodySpec DEXA body scan is a valuable complement (not a diagnostic test).
