DEXA Scan (DXA): Bone Density and Body Composition Testing

A clinician in a white coat explains something to a man in his sixties seated at a small wooden desk by a window — A clinician explains what a scan measures.

A DEXA (DXA) scan is a low-dose X-ray test used two ways: to measure bone density, and to measure body composition (fat and lean mass) across the whole body. A bone-density exam typically takes 10 to 30 minutes [1] and uses approximately 0.001 to 0.013 mSv of radiation, depending on the scanner and body part [2].

Overview

DEXA (also written DXA) stands for dual-energy X-ray absorptiometry, a low-dose X-ray scan used two ways: to measure bone mineral density at the hip and spine, and to measure body composition: the whole-body split between fat mass and lean mass, sometimes called a body composition scan. The same scanner technology performs both tests [3][4].

The bone-density version is what most guidelines mean by a bone density scan or bone density test [5][6]. The two uses have different evidence, different guideline support and different insurance rules. Bone-density DEXA and body-composition DEXA are different clinical tests that happen to use the same scanner type [3].

How a DEXA Scan Works

A DEXA scanner passes two different X-ray energy levels through the body while a person lies still on a table. Bone, fat and lean tissue absorb each energy level differently, and the difference lets the scanner separate bone mineral from soft tissue, and soft tissue into fat and lean components [4]. RadiologyInfo.org describes the bone-density test as "a quick and painless procedure" [1].

Why People Get a DEXA Scan

A bone-density DEXA is typically ordered to screen for osteoporosis or check fracture risk. Some people use body-composition DEXA to track changes in fat and lean mass during weight loss or a medically supervised program [3].

Professional guidance names a few specific clinical uses for body-composition DEXA. ISCD lists checking fat distribution in people with HIV taking antiretroviral drugs linked to fat loss (lipoatrophy), and tracking fat and lean mass in people with obesity who are having bariatric surgery, or who are on medical, diet or weight-loss regimens with anticipated large weight loss, once weight loss exceeds about 10% [3]. ISCD adds that the impact on clinical outcomes is uncertain for the bariatric and diet uses [3]. Other guidance names two more uses: in European sarcopenia guidance, confirming low muscle mass once low strength has been found [7]; and, as one of several accepted options, confirming excess body fat when diagnosing obesity [8].

What a DEXA Scan Measures

A DEXA scan produces different outputs depending on the type performed. A bone-density DEXA reports bone mineral density as a T-score. A body-composition DEXA reports fat mass, lean mass, percent body fat and, on many systems, an optional estimate of visceral fat [3][9].

These are estimates, and a licensed clinician interprets the results [10].

DEXA scanners are regulated by FDA as medical devices (Class II). The Body Composition Software Option for GE Lunar DEXA Bone Densitometers (GE Medical Systems Lunar, K071570) was cleared through FDA's 510(k) process for prescription use. Its cleared indications say the software 'measures the regional and whole body bone mineral density (BMD), lean and fat tissue mass and calculates derivative values' such as body-fat percentage, and that it 'does not diagnose disease, or recommend treatment regimens, or quantify treatment effectiveness. Only the health care professional can make these judgments.'

Output	What it means	Limitation
Bone mineral density (BMD), hip and spine	Reported as a T-score. T-score ≤ −2.5 = osteoporosis; −1.0 to −2.5 = low bone mass (osteopenia); ≥ −1.0 = normal, using WHO criteria applied by BHOF and ISCD	Criteria apply to postmenopausal women and men 50+; younger adults use different (Z-score) criteria, not covered on this page [3][6]
Fat mass	Total and regional fat, by region (for example trunk and legs), estimated from X-ray attenuation	In one study of 51 weight-stable adults on a GE Lunar iDXA, a change smaller than about 2.76 kg across a 3-month study could be measurement noise (95% least significant change); compare scans from the same scanner [9]
Lean (fat-free) soft-tissue mass	Total and regional lean tissue; used in some muscle-loss (sarcopenia) evaluations	In the same study, a change smaller than about 2.37 kg across 3 months could be measurement noise; hydration status can affect the reading [7][9]
Visceral adipose tissue (VAT), estimated	An estimate of fat around internal organs	Correlated closely with CT in validation studies that were manufacturer-funded or had manufacturer-employed authors [11][12]. Repeat-scan reliability is poor; see Accuracy & Limitations [3][9]
Android/gynoid ratio, trunk-to-leg fat ratio, lean mass index, fat mass index	Additional indices some facilities report	ISCD: "The clinical utility of these measures is currently uncertain" [3]

Table sourced to [3][6][7][9][11][12]. Figures current as of the dates in References.

Evidence & Clinical Guidelines

The evidence behind DEXA differs sharply by use. Bone-density DEXA is supported by randomized-trial evidence; USPSTF describes central DXA as the most commonly used screening test, and the Bone Health & Osteoporosis Foundation calls hip and spine DXA the preferred method for diagnosing osteoporosis [5][6].

A 2017 paper on DXA body composition states that "DXA is the preferred method for bone and body composition" [4]. ISCD, though, lists only a few specific clinical uses for it and says the clinical utility of its additional measures, such as visceral fat and fat- and lean-mass indices, "is currently uncertain" [3].

USPSTF's pooled analysis of three randomized trials (42,009 women) found that bone-density screening, followed by treatment where appropriate, reduced hip fractures (relative risk 0.83, 95% CI 0.73 to 0.93) and major osteoporotic fractures (relative risk 0.94, 95% CI 0.88 to 0.99) over roughly 3.7 to 5 years, about 5 fewer hip fractures and 6 fewer major fractures per 1,000 women screened [5]. This trial evidence is in women; USPSTF found current evidence insufficient to judge screening in men [5].

One regional insurer's medical policy classifies whole-body DEXA body-composition studies as "investigational," citing insufficient evidence on health outcomes [13]. Separately, one large US observational study (NHANES, 9,471 adults aged 20 and older without major chronic disease at baseline, about 8.8 years of follow-up) found that adults in the highest quarter of DEXA-measured total body-fat percentage had higher all-cause mortality (hazard ratio 1.48, 95% CI 1.07 to 2.04) than those in the second-lowest quarter [14]. This is an association from observational data, not proof that body fat causes earlier death, and it says nothing about whether getting a scan changes outcomes. In searches of PubMed, Europe PMC and ClinicalTrials.gov on October 1, 2026, we found no randomized trial or systematic review that compared people who had a body-composition DEXA scan with people who did not on any health outcome. ClinicalTrials.gov lists one registered randomized trial of a screening program for osteoporosis and sarcopenia in older adults (NCT05104034), with quality-of-life outcomes. Its status is unknown, no results were posted as of October 1, 2026, and it does not test body-composition scanning on its own [15]. See DEXA Body Composition vs. Bone Density Scan for a full comparison of what each scan reports and how insurance treats them differently.

Who Should Consider a DEXA Scan (and Who Shouldn't)

USPSTF recommends screening for osteoporosis in women 65 and older and in postmenopausal women younger than 65 who are at increased risk for an osteoporotic fracture as estimated by clinical risk assessment (a grade B recommendation), and concluded with moderate certainty that this screening has moderate net benefit [5]. Central DEXA is the most commonly used screening test [5].

Evidence is currently insufficient to recommend for or against screening men, according to the same 2025 guideline [5]. In searches of PubMed and Europe PMC on October 1, 2026, we found no clinical practice guideline that recommends routine body-composition DEXA scans for healthy adults. One 2020 position paper from the Italian College of Academic Nutritionists (ICAN-49), which is not a clinical practice guideline, suggests that adults older than 65 have a handgrip-strength test first, then a DXA scan if grip is weak and a bioimpedance test to confirm low muscle mass [16]. See Why People Get a DEXA Scan for the narrow situations professional guidance does name [3].

Anyone who is or may be pregnant should tell the facility before any DEXA scan [1]. Anyone who has recently had a barium exam, or contrast imaging for CT or a radioisotope scan, may need to wait 10 to 14 days before a DEXA test, per patient-preparation guidance [1].

Accuracy & Limitations

DEXA's precision (repeat-scan consistency on the same machine) and its accuracy (agreement with a reference method) are different questions. In one study on a GE iDXA scanner, changes smaller than about 2.76 kg of fat or 2.37 kg of lean mass across 3 months could be measurement noise, and visceral-fat readings were far less repeatable [9].

In one GE iDXA study of weight-stable adults, visceral-fat readings varied by about 16% between same-day rescans (30 adults) and by about 42% over 3 months (51 adults) [9]. The authors advise that changes in visceral fat below 500 grams be interpreted with caution because of this poor precision [9]. The studies validating DEXA's visceral-fat estimate against CT scans were funded by, or had authors employed by, the scanner manufacturers [11][12].

Results from different scanners are not directly comparable, even between models from the same manufacturer. In one 2026 study of 101 adults scanned the same day on three scanners, converting body-fat percentage between devices left biases ranging from about 1 percentage point (GE iDXA to Hologic Discovery) to about 4.2 points (Hologic Discovery to Hologic Horizon) [17]. ISCD states that no phantom has been identified that removes systematic body-composition differences between manufacturers [3]. Compare your own results only against scans from the same machine and facility [3][9][17].

At the group level, DEXA's body-fat estimates correlate closely with the multi-compartment models used as the research reference, but many studies have found systematic differences, such as underestimating body fat in leaner people [18][19]. In the studies we reviewed, DEXA readings for individuals ranged from about 3 percentage points above to about 7 percentage points below the reference [19][20][21], and varied with body size and leanness.

ISCD's minimum acceptable precision standards translate to a least-significant-change of about 5.0% to 6.9% depending on the site (hip, spine, femoral neck) at the same facility. A smaller change on the same machine may be measurement noise rather than a real change in bone density [3]. These figures are ceilings for minimum acceptable precision, not typical values, and apply to bone mineral density only; each facility calculates its own least-significant-change from its own precision study [3]. Results are not comparable between machines that have not been cross-calibrated [3][6].

Risks: Radiation Exposure

A DEXA scan uses a very small dose of ionizing radiation. For a bone-density scan, a 2010 review gives approximately 0.001 mSv on first-generation pencil-beam scanners and 0.009 to 0.013 mSv on modern fan-beam Hologic scanners (hip to spine) [2]. RadiologyInfo.org lists 0.001 mSv as typical and compares it to about 3 hours of background radiation [22].

A whole-body body-composition scan uses under 10 microsieverts (approximately 0.01 mSv), which one research review compares to about one day of natural background radiation at sea level [4].

Scan type	Typical effective dose	How it compares	Source
Bone-density DEXA, adult, fan-beam (Hologic), hip	approximately 0.009 mSv	n/a	Damilakis 2010 [2]
Bone-density DEXA, adult, fan-beam (Hologic), spine	approximately 0.013 mSv	n/a	Damilakis 2010 [2]
Bone-density DEXA, first-generation pencil-beam scanner	approximately 0.001 mSv	n/a	Damilakis 2010 [2]
Bone densitometry, RadiologyInfo typical value for an average-sized adult	0.001 mSv	about 3 hours of natural background radiation	RadiologyInfo.org, Radiation Dose page [22]
Whole-body body-composition DEXA scan	approximately 0.004 to 0.008 mSv (Hologic models); under 10 microsieverts overall	about one day of natural background radiation at sea level, per Shepherd 2017	Damilakis 2010 [2]; Shepherd 2017 [4]

Effective-dose figures are approximate and vary by scanner model, site and body size. A DEXA scanner's actual dose depends on its generation (older pencil-beam scanners use lower doses than modern fan-beam scanners) and which body part or scan type is performed. Figures dated as cited; accessed 2026-09-27.

A 2010 review of radiation in osteoporosis imaging states that every exam should be clinically justified and that dose matters more for children than for adults [2]. The Bone Health & Osteoporosis Foundation calls DEXA radiation "trivial amounts," and USPSTF describes screening as using "low doses of radiation" [5][6].

If you have a medical emergency, call 911. Problems with medical devices, including imaging equipment, can be reported to FDA through MedWatch.

FDA Clearance and Clinician Orders

DEXA scanners are FDA-regulated medical devices (Class II). Manufacturers market them through FDA's 510(k) clearance process. [23][24] Clearance is not the same as approval: FDA's own rule states that a 510(k) determination "does not in any way denote official approval of the device" [25].

The software option described earlier on this page is one example for one manufacturer's scanners, not a statement about every DEXA scanner or software version on the market.

Some DEXA facilities require a clinician's order (a referral) before a scan; requirements vary by state and facility. Ask the facility what it requires before you schedule.

Regulatory status checked September 27, 2026. Sources: www.govinfo.gov/…/CFR-2025-title21-vol8-sec892-1170.xml; www.accessdata.fda.gov/…/K252718.pdf; www.accessdata.fda.gov/…/K071570.pdf; www.govinfo.gov/…/CFR-2025-title21-vol8-sec807-97.xml; www.fda.gov/…/it-really-fda-approved

How to Prepare for a DEXA Scan

Preparation depends on which DEXA scan you're having. For a bone-density exam, avoid calcium supplements for at least 24 hours beforehand, wear clothing without metal, and tell the technologist if you've recently had a barium exam or contrast imaging, since you may need to wait 10 to 14 days [1].

Body-composition results are more comparable between visits when conditions are standardized: resting, fasting overnight, wearing minimal clothing, and using a consistent scan position, per published DEXA methodology guidance [3][26]. Facility instructions govern what to do before your appointment.

How Often Should You Get a DEXA Scan

No single interval applies to every DEXA scan. It depends on which test you're having and why. Cohort studies reviewed by USPSTF suggest that repeating a bone-density test after 4 to 8 years does not add accuracy in predicting fractures, and evidence on screening intervals is limited [5].

For patients on osteoporosis treatment, the Bone Health & Osteoporosis Foundation suggests re-testing 1 to 2 years after starting or changing therapy, then at intervals based on individual circumstances [6]. In searches of PubMed and Europe PMC on October 1, 2026, we found no clinical practice guideline that sets how often healthy adults should repeat a body-composition DEXA scan. For people having metabolic and bariatric surgery, a 2025 review from the American Society for Metabolic and Bariatric Surgery (ASMBS) suggests a DEXA scan before surgery and another one year after [27]. Because of the measurement variability described in Accuracy & Limitations, scans repeated too close together on the same machine may show a difference that isn't real change rather than genuine progress [9].

Typical Appointment

A bone-density DEXA exam is usually completed within 10 to 30 minutes, according to RadiologyInfo.org [1]. During the exam, you lie on a padded table and hold still while an imaging detector positioned above you records the scan [1]. In a 2024 comparison of two scanners in 926 postmenopausal women (mean age 72.9 years), the total-body scan took 7 minutes 16 seconds to 13 minutes 16 seconds on a GE Lunar iDXA, depending on the patient's body shape, and 2 minutes 54 seconds on a Hologic Horizon A [28]. Ask the facility how long your scan will take.

Cost

DEXA scan prices are not listed on this page because we do not yet have dated, sourced prices for this test. Prices can differ by scan type (bone density or body composition), by the kind of facility and by location.

Find a Provider

Some facilities require a clinician's order. Requirements vary.

Insurance

Insurance coverage differs by which DEXA scan you're having. Medicare covers bone-density testing once every 24 months, or more often if medically necessary, for people who meet at least one of Medicare's listed conditions, for example a woman whose doctor determines she is estrogen-deficient and at risk for osteoporosis, or a person taking prednisone or steroid-type drugs [29].

At least one regional insurer's medical policy currently classifies whole-body body-composition DEXA as investigational [13].

Purpose	Coverage stated by this source	Condition	Source
Bone-density DEXA (Medicare)	Yes, once every 24 months	For people who meet at least one of Medicare's listed conditions; more often if medically necessary	Medicare.gov [29]
Body-composition DEXA (one regional payer example)	No, classified "investigational"	Capital Blue Cross medical policy, effective 2026-03-01; cites insufficient outcome evidence	Capital Blue Cross MP 5.037 [13]

Coverage varies by payer, plan and state. These are two documented examples, not a national rule for every insurer. Confirm with your specific plan before scheduling.

Alternatives: DEXA vs. Other Body-Composition Methods

DEXA is one of several body-composition methods; bioimpedance (BIA), air-displacement plethysmography and anthropometric equations are the main alternatives. In one study of 170 healthy adults, DEXA and air-displacement plethysmography, each assessed separately, had narrower limits of agreement (≤4.8 percentage points for body fat) than bioimpedance (≤6.2), though bioimpedance's average error was smaller at the group level [21].

Method	Compared with	95% limits of agreement (% body fat)	Population / source
Multi-compartment models (same body-volume & total-body-water inputs)	5-component reference model	≤ 0.9 percentage points	170 healthy adults, Tinsley 2021 [21]
DEXA; air-displacement plethysmography (each assessed separately)	5-component reference model	≤ 4.8 percentage points	170 healthy adults, Tinsley 2021 [21]
Bioimpedance technologies (device models not named in the abstract)	5-component reference model	≤ 6.2 percentage points	170 healthy adults, Tinsley 2021 [21]
Anthropometric equations	5-component reference model	≤ 10.6 percentage points	170 healthy adults, Tinsley 2021 [21]

Limits of agreement (LOA) describe the range within which most individual estimates fall compared with the reference method; a narrower LOA means closer individual-level agreement. Figures are from one 2021 study of 170 healthy adults and may not generalize to other groups [21]. A separate 2026 systematic review of 12 studies in healthy adults found that bioimpedance's limits of agreement against a 4-compartment model typically spanned 15 to 20 percentage points for body-fat percentage [30]. The two studies may report limits of agreement differently, so their figures should not be compared directly.

See DEXA vs. InBody for a full, sourced comparison, including which factors may matter for different goals.

Questions to Ask a Provider

Questions worth asking before you schedule:

Is this a bone-density scan, a body-composition scan, or both?
Will my follow-up scan be done on the same machine, at the same facility?
Do I need a doctor's order for this scan at your facility, and in this state?
How is visceral fat estimated on your specific device, and what's its typical measurement variability?
What preparation do you require (fasting, clothing, timing around supplements or recent contrast imaging)?
What is included in the price, and do you accept my insurance for this specific test?

FAQs

How long does a DEXA scan take?

A bone-density DEXA exam usually takes 10 to 30 minutes, according to RadiologyInfo.org [1]. Scan time depends on the scanner. In one 2024 study of 926 postmenopausal women, a total-body scan took 7 minutes 16 seconds to 13 minutes 16 seconds on a GE Lunar iDXA and 2 minutes 54 seconds on a Hologic Horizon A [28]. Ask the facility when you schedule.

How should I prepare for a DEXA body-composition scan?

Published DEXA methodology guidance recommends standardized conditions (rested, fasted overnight, minimal clothing, consistent positioning) so body-composition results are more comparable between visits [3][26]. Bone-density DEXA has its own preparation steps, including avoiding calcium supplements for at least 24 hours beforehand [1]. Follow your facility's instructions.

How often should you get a DEXA scan?

There is no single answer. Cohort studies reviewed by USPSTF suggest that repeating bone-density testing after 4 to 8 years does not add accuracy in predicting fractures [5], and Medicare covers it once every 24 months for people who qualify [29]. In searches of PubMed and Europe PMC on October 1, 2026, we found no clinical practice guideline that sets how often healthy adults should repeat a body-composition DEXA scan.

Does a DEXA scan measure visceral fat?

Yes. A DEXA scan can estimate visceral fat, the fat around internal organs. In validation studies that were manufacturer-funded or had manufacturer-employed authors, the estimate correlated closely with CT scans [11][12]. Repeat measurements vary, though: about 16% between same-day rescans in one GE iDXA study, and the authors advise caution in interpreting changes below 500 grams [9]. ISCD says the clinical utility of DEXA visceral-fat measures is currently uncertain [3].

Nearby Providers

This section will show DEXA-scan providers near you once our directory includes them for your area.