DEXA Scan
The gold standard assessment for bone mineral density, body fat percentage, and lean muscle mass
Quick Answer
Dual-energy X-ray absorptiometry (DEXA) is the gold standard for measuring bone mineral density and body composition. It provides precise measurements of bone density (for osteoporosis risk), body fat percentage, lean muscle mass, and visceral fat, all key markers for longevity. The scan takes 7-15 minutes, uses minimal radiation, and gives you actionable data about skeletal and metabolic health. Recommended annually for those over 50 or anyone tracking body composition changes.
High Evidence
Strong clinical trial data in humans
Safety: DEXA uses very low radiation (less than a day of natural background exposure) and is considered extremely safe. No injections or invasive procedures.
What Is This?
DEXA (Dual-Energy X-ray Absorptiometry, also called DXA) is an imaging technique that uses two low-dose X-ray beams to measure:
Bone Mineral Density (BMD):
- T-score compares your bone density to a healthy 30-year-old
- Z-score compares to others your age/sex
- Identifies osteopenia (low bone mass) and osteoporosis
- Predicts fracture risk
- Total body fat percentage
- Regional fat distribution (android/gynoid ratio)
- Visceral adipose tissue (VAT), the dangerous abdominal fat
- Lean mass (muscle + organs + water)
- Appendicular lean mass (arms + legs), key for sarcopenia assessment
- Highly accurate and reproducible
- Distinguishes between fat, lean tissue, and bone
- Regional analysis shows where fat and muscle are distributed
- Tracks changes over time with precision
- Low radiation, quick, non-invasive
- Bone T-score (goal: >-1.0)
- Body fat percentage (optimal varies by age/sex)
- Visceral fat (lower is better)
- Appendicular lean mass index (ALM/height²), for sarcopenia risk
How It Works
DEXA provides insights that scales, BMI, and even calipers cannot:
Bone Health Assessment: Bone loss occurs silently until a fracture happens. DEXA detects osteopenia and osteoporosis early, allowing intervention before fractures occur. Low bone density increases mortality risk, hip fractures in the elderly have 20-30% one-year mortality.
Beyond BMI: BMI cannot distinguish between fat and muscle. A muscular person and an obese person can have identical BMI. DEXA reveals the truth: body fat percentage and, critically, where fat is distributed.
Visceral Fat Matters: Visceral adipose tissue (VAT), fat around organs in the abdomen, is metabolically active and strongly associated with:
- Insulin resistance and diabetes
- Cardiovascular disease
- Inflammation
- Mortality
Sarcopenia Detection: Sarcopenia (age-related muscle loss) predicts frailty, falls, disability, and mortality. DEXA measures appendicular lean mass, allowing calculation of sarcopenia risk indices. Early detection enables intervention through resistance training and nutrition.
Tracking Changes: DEXA's reproducibility makes it ideal for tracking body composition changes. If you're building muscle or losing fat, DEXA confirms whether your interventions are working, far more accurately than scales.
How to Start
Find a DEXA facility
DEXA scans are available at hospitals, radiology centers, universities, and fitness-focused clinics. Body composition scans may require different facilities than medical bone density scans.
Tips:
- •Search "DEXA body composition" + your city
- •BodySpec, DexaFit, and similar services specialize in body composition
- •Hospital/radiology for bone density with physician referral
- •Prices range $50-200 for body composition, often covered by insurance for bone density
Prepare for your scan
Preparation is minimal. Wear comfortable clothes without metal. Stay hydrated consistently in the days before (hydration affects lean mass readings). Avoid exercise and large meals right before scanning.
Tips:
- •No metal zippers, buttons, or underwire
- •Consistent hydration for reliable readings
- •Same time of day for repeat scans
- •Avoid strenuous exercise 24 hours before
Get scanned
You'll lie still on a padded table while the scanner arm passes over you. The whole-body scan takes 7-15 minutes. It's completely painless, you won't feel anything.
Tips:
- •Remove all metal objects
- •Lie still and breathe normally
- •Full body scan for composition; spine/hip for bone density
- •Ask for visceral fat (VAT) quantification
Interpret results and act
Review bone density T-scores, body fat percentage, lean mass, and visceral fat. Compare to optimal ranges and your prior scans. Create an action plan for any concerning findings.
Tips:
- •Bone T-score: normal >-1.0, osteopenia -1.0 to -2.5, osteoporosis <-2.5
- •Body fat: varies by age/sex, generally <25% for men, <35% for women optimal
- •Track appendicular lean mass for sarcopenia risk
- •Visceral fat: lower is better, strongly associated with metabolic disease
What to Expect
Quick, painless procedure
The scan itself takes 7-15 minutes. You'll lie on a table while the scanner passes over you. No injections or discomfort.
Results available
Body composition clinics often provide results immediately. Medical bone density scans may require physician interpretation and take 1-2 days.
Track changes
Annual scans reveal trends in bone density and body composition. More frequent scanning (every 6 months) if actively changing diet or exercise.
Intervention monitoring
Use DEXA to verify that your interventions (strength training, nutrition, medications) are working. Objective data beats subjective assessment.
Practical Details
Timing
Anytime, but be consistent for serial measurements (same time of day, similar hydration). Morning is often preferred.
Duration
Baseline scan, then annual monitoring. Every 6 months if actively optimizing body composition or treating bone loss.
Cost
$50-200 per scan
Body composition scans at fitness-focused facilities cost $50-150. Medical bone density scans through radiology may be covered by insurance for those over 65 or with risk factors. Self-pay bone density scans range $100-250.
Risks & Considerations
Potential Risks
- •Very low radiation exposure (equivalent to a few hours of natural background)
- •Not recommended during pregnancy (precautionary)
- •Metal implants may affect accuracy in that region
- •Over-interpretation of small changes (measurement error exists)
Possible Side Effects
- •None, the scan is completely non-invasive
Who Should Avoid This
- •Pregnancy (precautionary, radiation is minimal)
- •Recent barium or contrast studies (wait 7 days)
- •Inability to lie flat and still
Key Research
DXA as a standard for measuring bone and body composition
Journal of Clinical Densitometry, 2017
Comprehensive review confirming DEXA as the preferred method for measuring bone density and body composition due to accuracy, precision, and low radiation.
View StudySarcopenia and mortality risk in older adults
Journal of Cachexia, Sarcopenia and Muscle, 2022
Meta-analysis showing sarcopenia (low muscle mass measured by DEXA) is associated with significantly increased mortality risk in older adults, independent of other factors.
View StudyVisceral adipose tissue and cardiometabolic risk
Nature Reviews Endocrinology, 2020
Review establishing visceral fat (quantifiable by DEXA) as a key driver of metabolic disease, independent of total body fat.
View StudyFrequently Asked Questions
How accurate is DEXA compared to other methods?
DEXA is the gold standard for body composition with error rates of 1-2% for fat mass. Bioimpedance scales have 5-10% error. Calipers depend heavily on technique. For bone density, DEXA is the clinical standard, no comparison.
How often should I get a DEXA scan?
Annual scans are sufficient for most people. If actively changing body composition (new exercise program, weight loss), every 6 months shows progress. For bone density on treatment, follow your physician's recommendation (often every 2 years).
Is the radiation dangerous?
No. DEXA uses extremely low radiation, about 0.001 mSv for a body composition scan. That's less than a day of natural background radiation and far less than a chest X-ray (0.1 mSv). Annual scans pose negligible risk.
What's a good body fat percentage?
Optimal varies by age and sex. General targets: Men: 10-20% (athletic: 6-13%, fitness: 14-17%, acceptable: 18-24%). Women: 18-28% (athletic: 14-20%, fitness: 21-24%, acceptable: 25-31%). Lower isn't always better, extremely low body fat has health risks.
Can DEXA detect visceral fat?
Yes, modern DEXA with CoreScan or similar software quantifies visceral adipose tissue (VAT) in the trunk. This is one of the most valuable measurements, visceral fat is strongly associated with metabolic disease independent of total body fat.
Sources
- RadiologyInfo: Bone Density Scan (DEXA)(guideline)
- CDC: Facts About Bone Density DEXA Scan(guideline)
- Cleveland Clinic: DXA Scan(guideline)
Related Interventions
Disclaimer: This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider before starting any new health practice or supplement. Evidence levels and recommendations can change, this content was last updated December 2025.