DEXA Scan: What It Measures, Cost, Preparation & How to Read Results
The gold-standard bone density test — procedure, interpretation, and what your T-score means
DEXA measures bone mineral density in minutes with minimal radiation. Understand cost, prep, Medicare, body-composition add-ons, and how T-scores map to osteopenia or osteoporosis.
DEXA (also written as DXA) uses two low-dose X-ray beams at different energy levels to distinguish between bone and soft tissue. By measuring how much each beam is absorbed, the scanner calculates bone mineral density (BMD) in grams per square centimeter (g/cm²) at the lumbar spine (L1-L4), femoral neck, and total hip — the sites most predictive of fracture risk.
The scan takes 10-20 minutes, requires no injection or fasting, involves minimal radiation exposure (about 1/10th of a standard chest X-ray), and is the only test accepted by the WHO for diagnosing osteoporosis. Modern DEXA scanners also measure body composition — lean mass, fat mass, and visceral fat — making them useful for fitness and metabolic assessment beyond bone health.
For what the numbers mean after your scan, read T-score and Z-score explained, then osteopenia vs osteoporosis. For prevention around the menopause transition, start with bone density and menopause. Broader lab context: lab testing and biomarkers.
What a DEXA Scan Measures
- Bone mineral density (BMD): Measured in g/cm² at the lumbar spine, femoral neck, total hip, and sometimes the distal radius. Results are reported as T-scores and Z-scores.
- T-score: Compares your BMD to the average BMD of a healthy 30-year-old. T-score of 0 = average peak bone mass. Each -1.0 increment represents ~10-12% lower bone density and approximately doubles fracture risk.
- Z-score: Compares your BMD to the average for your age and sex. A Z-score below -2.0 suggests bone loss beyond normal aging and warrants investigation for secondary causes.
- Body composition (optional): Total body DEXA measures lean mass, fat mass, bone mineral content, and visceral adipose tissue (VAT) with research-grade accuracy. This is increasingly used for fitness assessments and metabolic risk evaluation.
How to Prepare
- Clothing: Wear loose, comfortable clothing without metal zippers, buttons, or underwire. You may be asked to change into a gown.
- Calcium supplements: Stop calcium supplements 24 hours before the scan — calcium tablets in the GI tract can falsely elevate spine BMD readings.
- Contrast agents: Wait at least 7 days after any barium or gadolinium contrast study before a DEXA scan.
- No fasting required.
- Remove metal: Belt buckles, jewelry near scan sites, and metal clasps should be removed.
- Consistency: For follow-up scans, use the same machine and facility when possible. BMD values vary between manufacturers, so trending requires consistent equipment.
Cost and Insurance Coverage
Average cost: $150-$400 without insurance. Medicare covers a bone density test every 2 years for women 65+ and for certain high-risk individuals. Most private insurance covers DEXA when ordered for appropriate indications (postmenopausal, risk factors, fracture history, long-term corticosteroid use).
Medicare coverage: Covered every 24 months for women 65+, estrogen-deficient women at risk, individuals with vertebral abnormalities, those on long-term glucocorticoid therapy, and patients with primary hyperparathyroidism. A physician order is required.
Body composition DEXA: Typically $75-$200 and is usually self-pay/cash. Insurance generally does not cover DEXA when ordered solely for body composition assessment.
How to Interpret Your Results
| T-Score | Diagnosis | Fracture Risk | Typical Action |
|---|---|---|---|
| Above -1.0 | Normal | Baseline | Rescreen per guidelines (age/risk dependent) |
| -1.0 to -1.5 | Mild osteopenia | 1.5-2x baseline | Lifestyle intervention, recheck 2 years |
| -1.5 to -2.5 | Moderate osteopenia | 2-4x baseline | Aggressive lifestyle intervention + FRAX assessment |
| Below -2.5 | Osteoporosis | 4-8x baseline | Pharmacological treatment usually indicated |
Key points: The spine T-score can be falsely elevated by degenerative changes (arthritis, disc disease) in patients over 65, which is why the hip is often more reliable in older adults. Compare results at the same site over time — spine-to-spine, hip-to-hip. A change of 3-5% between scans is needed to be clinically significant (exceeds the scanner's precision error).
Frequently Asked Questions
Can a DEXA scan show cancer?
A DEXA scan is not designed to detect cancer. It measures bone density, not bone structure or tumors. However, in some cases, significant asymmetry or unexpected density changes may prompt further imaging (CT or MRI). Cancers that affect bone (multiple myeloma, bone metastases) can lower bone density, but DEXA alone cannot diagnose them. If cancer is a concern, dedicated imaging and lab tests are needed.
How much is a DEXA scan?
A standard bone density DEXA scan costs $150-$400 without insurance. Medicare covers one every 2 years for qualifying patients (women 65+, high-risk individuals). Private insurance typically covers it with appropriate medical indication. Body composition DEXA (lean mass, fat mass, visceral fat) is usually $75-$200 and is typically self-pay.
How long does a DEXA scan take?
A standard DEXA scan takes 10-20 minutes total. The actual scanning time is 3-7 minutes per site (spine and hip). A total body composition scan adds another 5-10 minutes. There is no recovery time — you can resume normal activities immediately.
Does Medicare cover DEXA scan?
Yes. Medicare covers a bone density DEXA scan every 24 months for: women age 65 and older, estrogen-deficient women at clinical risk for osteoporosis, individuals with vertebral abnormalities on imaging, patients receiving or planning long-term glucocorticoid therapy, and patients with primary hyperparathyroidism. A physician order is required.
How accurate are DEXA scans?
DEXA is the gold standard for bone density measurement with a precision error of 1-2% at the spine and 1.5-3% at the hip. This means a true change in bone density must exceed 3-5% to be distinguishable from measurement variability. For best accuracy: use the same machine for follow-up scans, ensure proper positioning, and avoid calcium supplements 24 hours before testing.
What to wear for a DEXA scan?
Wear loose, comfortable clothing without metal components — no metal zippers, underwire bras, belt buckles, or metal buttons near the scan area. Athletic wear or scrubs are ideal. You may be asked to change into a hospital gown. Remove jewelry, watches, and any metal objects before the scan.
How to interpret DEXA scan results?
Focus on the T-score: above -1.0 is normal, -1.0 to -2.5 is osteopenia, below -2.5 is osteoporosis. Compare to your previous scan at the same site (spine-to-spine, hip-to-hip). A change of 3-5% between scans is clinically meaningful. Also review your FRAX score (10-year fracture risk calculation). In patients over 65, hip T-scores may be more reliable than spine due to degenerative changes that falsely elevate spine readings.
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