How a DEXA Scan Works: A Simple, Accurate Guide

Want the quick answer? A DEXA (DXA) scan uses two very low‑dose X‑ray beams to separately measure your bone, fat, and lean tissue while you lie still for about 6–10 minutes.

In the guide below, we’ll show you how the technology works, what a BodySpec scan measures, how to prepare, radiation safety basics, and how to use your numbers to make smarter training and health decisions.

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How DEXA technology works (simple version)

Here’s the “how” in everyday terms:

1. Two beams, two energies. The scanner arm emits a low‑energy beam and a slightly higher‑energy beam.
2. Different tissues = different dimmers. Bone blocks (attenuates) the beams the most, lean tissue less, and fat the least.
3. Sensitive detectors measure the leftovers. The system captures how much of each beam makes it through each tiny spot (pixel).
4. Smart software labels the pixels. By comparing the two signals, the software classifies each pixel as bone mineral, fat mass, or lean mass and then totals them by body region.

For a more technical explanation, see professional overviews from RadiologyInfo and NCBI/StatPearls.

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Full‑body DEXA vs. central (diagnostic) DEXA

• Full‑body DEXA (BodySpec): A wellness scan that maps fat, lean, and overall bone metrics across the entire body. Great for tracking body composition, VAT, and muscle balance over time. Your report provides comprehensive data you can review and share with your doctor.
• Central (diagnostic) DEXA: A medical test focused on the hip and spine—and in some cases the forearm (radius)—to diagnose osteoporosis using T‑scores and Z‑scores, and sometimes to screen for vertebral fractures with Vertebral Fracture Assessment (VFA), as described by RadiologyInfo and Johns Hopkins Medicine.

BodySpec specializes in full‑body wellness scans rather than physician‑ordered diagnostic tests. If you need osteoporosis testing, talk to your clinician about a central DEXA of the hip and spine (and occasionally the forearm).

If you’re reviewing a clinical bone density report, our guide to interpreting DEXA T‑scores and Z‑scores can help.

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What a BodySpec DEXA scan measures

A single 6–10 minute scan produces a detailed report:

• Body fat percentage: Total and by region (arms, legs, trunk) to track real fat‑loss progress.
• Lean mass: How much muscle you carry in each region, which helps spot left/right or upper/lower asymmetries.
  • Note: “Lean mass” includes more than muscle (it also includes organs and body water). Keeping hydration and routine consistent before each scan improves apples‑to‑apples comparisons (UC Davis Health; Will drinking water affect my scan?).
• Visceral adipose tissue (VAT): Deep belly fat around organs—higher VAT is linked to elevated cardiovascular and metabolic risk, as summarized in a 2023 review on visceral fat and residual cardiovascular risk.
• Android vs. gynoid fat pattern: Where you store fat (waist vs. hips/thighs), adding context for goals and health risk.
• Whole‑body bone metrics (non‑diagnostic): BodySpec reports a whole‑body bone mineral metric for trends. This is not the same as a clinical, site‑specific BMD from a central DEXA of the hip/spine and shouldn’t be compared directly. If you notice a concerning downward trend in your whole‑body bone number, share it with your doctor to decide whether a central DEXA is appropriate, per guidance from RadiologyInfo and UC Davis Health.

Step‑by‑step: What happens during your scan

1. Prep smart. Wear light, metal‑free clothing; remove jewelry and belts. For best consistency, follow this checklist: Prepare for your BodySpec scan. If you take calcium supplements, skip them for 24 hours before your scan, as noted by RadiologyInfo.
   • Note on recent imaging: After iodinated CT contrast, many centers wait at least 72 hours; after a barium study, 10–14 days is often recommended to avoid artifacts, according to Johns Hopkins Medicine and RadiologyInfo.
2. Get positioned. You’ll lie on a padded table in an open room (no tunnel). Our technologist positions your arms/legs for clear images.
3. Scan time. The overhead arm glides from head to toe while you breathe normally and stay still. The scan itself takes about 6–10 minutes.
4. Results arrive fast. You’ll receive your digital report shortly after.

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Is a DEXA scan safe? A quick radiation reality check

DEXA uses a very small amount of ionizing radiation. For context, a BodySpec whole‑body scan is typically about 4–5 µSv (microsieverts) —as detailed in our BodySpec radiation guide—and it’s in the same ballpark as a dental X‑ray and well below many everyday exposures. Reference dose ranges are also summarized by RadiologyInfo.

Special notes:

• Pregnancy: Elective DEXA is generally deferred during pregnancy; inform your technologist if you could be pregnant, per the CDC.
• Recent contrast studies: Follow your provider’s timing guidance, especially after barium or nuclear medicine exams, as outlined by RadiologyInfo.

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Why choose DEXA over other methods?

• DEXA vs. BMI: BMI can misclassify muscular people and miss high‑fat, normal‑weight cases. DEXA directly separates fat, lean, and bone. Learn more: Body composition vs. weight: what matters for your health.
• DEXA vs. BIA (smart scales/InBody): BIA infers body fat from electrical conductivity and is sensitive to hydration and meal timing. Research comparing methods confirms DEXA’s stronger agreement for fat and fat‑free mass at the individual level.
• It provides valuable bone‑health trend data. While not diagnostic, you can share your whole‑body bone number with your clinician to decide if further testing, such as a central DEXA, is needed, per RadiologyInfo.

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Why choose BodySpec for your DEXA scan?

• Affordable, no referral required. See our Pricing & Packages for current rates and memberships.
• Accuracy you can trust. BodySpec uses modern GE iDXA systems, which demonstrate about 1% test–retest variation for total‑body fat mass—meaning repeated measurements are highly consistent. We add twice‑daily phantom checks, fleet harmonization, and in‑house maintenance to keep scanners tightly calibrated—practices that help you reliably detect even small changes in your results (details in our BodySpec DEXA Scan Accuracy Guide).
• Instant insights, anytime. Receive your results the same day, and explore them at your own pace with our 24/7 AI agent in your dashboard, ready to explain your numbers and next steps in plain English.

How to use your results

• Track meaningful change every 8–12 weeks. You’ll see shifts in total body fat %, VAT, and segmental lean mass. Timing guide: When to get a DEXA scan (and how often).
• Watch VAT and android fat. These relate closely to metabolic risk. Learn more about what visceral fat is and explore practical strategies for how to lose it.
• Train with intent. Use segmental lean data to correct asymmetries. New to lifting? See strength training for beginners.

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FAQs

How long does a DEXA scan take?
About 6–10 minutes for the scan; plan ~15 minutes end‑to‑end.

What should I wear?
Light, metal‑free clothing. Remove jewelry, belts, and wearables.

Can I get a DEXA scan if I’m pregnant?
Elective scans are generally deferred during pregnancy. Inform your technologist if you could be pregnant, as the CDC advises.

Is BodySpec’s scan diagnostic for osteoporosis?
No. BodySpec offers non‑diagnostic, full‑body wellness scans. Diagnostic hip/spine DEXA (sometimes forearm) with T‑ and Z‑scores is ordered and interpreted by a clinician—resources like RadiologyInfo and Johns Hopkins Medicine outline the standard approach. If your whole‑body bone number trends down, bring it to your doctor to discuss whether a central DEXA is warranted.

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The takeaway

DEXA separates bone, fat, and lean tissue using dual‑energy X‑rays to deliver precise, low‑dose insights in minutes. With BodySpec’s rigorous quality controls and practical guidance, you can track what matters and adjust your plan with confidence.

Ready to see your numbers? Book your BodySpec DEXA scan.