How to Interpret Your DEXA Bone Density Result

What the DEXA Scan Actually Measures

DEXA, also written DXA, uses two X-ray energy levels to estimate the amount of mineral per unit area of bone. The report gives areal BMD in g/cm², together with standardized scores. It measures density, rather than every property of bone strength. [1,22]

T-Score: What It Compares

The T-score expresses how far BMD lies from the young-adult reference mean in standard deviations. A T-score of -1.0 is one standard deviation below that mean. A standard deviation is not a universal percentage of BMD across all sites and scanners. In Cummings and colleagues' study of 8,134 women aged 65 or older, each standard-deviation decrease in femoral-neck BMD was associated with a 2.6-fold increase in age-adjusted hip-fracture risk. That association describes the studied population, rather than a personal fracture probability. [4]

For postmenopausal women and men aged 50 or older, the densitometric categories are: [1]

A fracture history adds information beyond these categories. A hip or vertebral fracture can support osteoporosis treatment regardless of BMD under the U.S. Bone Health and Osteoporosis Foundation (BHOF) guide. [3]

Z-Score: What It Compares

A Z-score compares BMD with an age- and sex-matched reference, with population-specific reference data where available. ISCD prefers Z-scores in women before menopause and men younger than 50. A result of -2.0 or lower means below the expected range for age; it does not by itself establish a cause or a diagnosis of osteoporosis in a younger person. [1]

Low bone density can lead to assessment for contributing conditions or medicines. The Endocrine Society's guideline for men recommends laboratory assessment for contributing causes in men evaluated for osteoporosis. It does not turn a single Z-score into a universal laboratory panel. [6]

Understanding the WHO Diagnostic Thresholds

The WHO reference standard uses a femoral-neck T-score of -2.5 or lower. ISCD also permits diagnosis at the lumbar spine or total hip in postmenopausal women and men aged 50 or older, with the one-third radius available in specified circumstances. [1]

Low bone mass describes a BMD range. It does not necessarily mean high fracture risk. Age, prior fractures and other clinical factors change the risk at the same T-score. [1,5]

Why Site Selection Matters

The 1993 Study of Osteoporotic Fractures analysis followed 8,134 older women, with 65 hip fractures over a mean 1.8 years. Femoral-neck BMD predicted hip fracture better than spine or radius BMD. [4]

Spinal degeneration, calcification or a damaged vertebra can distort spine measurements. Scan quality and excluded vertebrae therefore matter when comparing the spine with the hip. FRAX uses femoral-neck BMD when BMD is entered; it does not use the lowest value from any scan site. [1,3,5]

Serial Scans and Least Significant Change

A numerical change between scans is meaningful only when measurement quality and precision support it. ISCD requires a facility to calculate its own least significant change (LSC), rather than rely on a manufacturer's precision estimate. A fixed 3-5% rule is not valid for every scanner, site or facility. [1]

The comparison should account for equipment and positioning. Results from different facilities or uncalibrated systems cannot automatically be treated as a true BMD trend. [1]

How to Use the FRAX Score Alongside Your T-Score

FRAX calculates 10-year probabilities for hip fracture and major osteoporotic fracture, incorporating clinical factors with or without femoral-neck BMD. The major-fracture outcome includes hip, clinical spine, forearm and proximal humerus fractures. Use the appropriate country model. [3,5]

Inputs include age, sex, body size, previous fracture, parental hip fracture, smoking, glucocorticoids, rheumatoid arthritis, secondary osteoporosis and alcohol intake of three or more units daily. FRAX probabilities and the diagnostic T-score answer different questions: absolute fracture risk and density classification. [5]

Treatment Thresholds in Major Guidelines

For postmenopausal women and men aged 50 or older, the 2022 BHOF guide recommends considering treatment with a T-score of -2.5 or lower at a diagnostic site, a hip or vertebral fracture regardless of BMD, or low bone mass at the femoral neck or total hip with U.S.-adapted FRAX hip risk of at least 3% or major-fracture risk of at least 20%. These are U.S. treatment thresholds, not a universal screening cutoff. [3]

The 2020 AACE/ACE guideline distinguishes high from very high fracture risk in postmenopausal osteoporosis. Very high-risk features include recent or multiple fractures, fractures during approved therapy, very low T-scores, high fall risk or very high calculated fracture probability. Risk stratification combines fracture history and other clinical factors with BMD. [2]

USPSTF Screening Recommendations

The January 2025 USPSTF recommendation supports screening women aged 65 or older and postmenopausal women younger than 65 who have increased fracture risk after clinical assessment. For younger women, risk factors inform whether to use a risk-assessment tool and proceed to DXA. The example 9.3% FRAX major-fracture probability is not a required screening threshold. Evidence remains insufficient to determine the balance of routine screening benefits and harms in men. [7]

What Raises Bone Density

Medicines and exercise can improve BMD, but a larger BMD increase does not translate directly into the same percentage reduction in fractures. Treatment trials also differ in baseline fracture risk, comparator and duration. [3]

Pharmacologic Options

In the FIT trial, 2,027 postmenopausal women with existing vertebral fractures received daily alendronate or placebo for three years. New radiographic vertebral fractures occurred in 8.0% versus 15.0%, respectively, a relative risk of 0.53. The hip-fracture relative hazard was 0.49 in this trial population; the report describes women with low bone mass and an existing vertebral fracture. [8]

The VERT trial of 1,226 women tested daily risedronate, not a 35 mg weekly schedule. The 5 mg daily group had a 49% relative reduction in new vertebral fractures over three years. In HORIZON, 7,765 women were randomized to annual 5 mg zoledronic acid or placebo; hip fractures occurred in 1.4% versus 2.5% over three years. [10,11]

Neer and colleagues randomized 1,637 women with prior vertebral fractures to daily parathyroid hormone (1-34) or placebo. At the 20 microgram dose, spine and femoral-neck BMD increased by 9 and 3 percentage points more than placebo, respectively, during a study with median observation of 21 months. These are between-group differences, rather than absolute gains at a fixed 18-month visit. [12]

ARCH enrolled 4,093 women with osteoporosis and a fragility fracture. It compared 12 months of monthly romosozumab with weekly alendronate, followed by alendronate in both groups. The sequential romosozumab group had fewer fractures; its findings apply to that treatment sequence and population. [13]

FREEDOM enrolled 7,868 women and compared denosumab every six months with placebo for three years. Radiographic vertebral fractures occurred in 2.3% versus 7.2%; hip fractures occurred in 0.7% versus 1.2%. The corresponding relative reductions were 68% and 40%. [14]

Lifestyle Interventions

Howe and colleagues' review included 43 randomized trials with 4,320 postmenopausal participants. Exercise produced small improvements in BMD, varying by exercise type and scan site. The pooled fracture result was inconclusive, rather than proof of a fixed annual BMD gain or fracture reduction. [15]

Calcium and vitamin D support normal bone metabolism. The National Academies sets calcium intake at 1,000 mg/day for women aged 19-50 and 1,200 mg/day from age 51; vitamin D intake is 600 IU/day through age 70 and 800 IU/day thereafter. These are total population intake targets, not automatic supplement prescriptions or deficiency-treatment doses. [23]

What Lowers Bone Density

The density result should be interpreted alongside medicines, hormone status, weight change and other conditions. [3]

Medications That Reduce BMD

Long-term glucocorticoid exposure is a recognized contributor. The 2022 ACR guideline recommends fracture-risk assessment, including BMD with vertebral assessment or spine imaging, for adults starting or continuing at least 2.5 mg/day of glucocorticoids for more than three months. Assessment includes clinical context, not DXA alone. [24]

In the ATAC bone substudy, anastrozole-treated women had median five-year decreases of 6.08% at the lumbar spine and 7.24% at the total hip. Those cumulative findings are not a constant annual loss rate. Androgen-deprivation therapy can also affect bone health; Shahinian and colleagues' prostate-cancer study measured fracture outcomes, rather than establishing a universal annual hip-BMD decline. [16,25]

Long-term proton-pump inhibitor use has been associated with fractures in observational studies. The BHOF guide lists PPIs among medicines relevant to an osteoporosis assessment. An association does not show that every person taking a PPI will lose bone density or that the medicine caused an individual fracture. [3]

Hormonal and Metabolic Drivers

Estrogen deficiency after menopause contributes to bone loss. In the original WHI estrogen-plus-progestin report, mean follow-up was 5.2 years and the hip-fracture hazard ratio was 0.66. That is a trial result for the studied hormone regimen, not a stand-alone reason to select hormone therapy. [17]

The Testosterone Trials bone substudy enrolled 211 older men with low testosterone. After one year, spine trabecular volumetric BMD rose by 7.5% with testosterone versus 0.8% with placebo. The primary measurement used quantitative CT, rather than the DEXA T-score. The study did not establish a reduction in fractures. [18]

Thyroid or parathyroid disorders, malabsorption and other conditions may contribute to low density. The assessment of secondary causes depends on the history, examination and clinical findings; a single low Z-score does not prescribe the same tests for everyone. [3,6]

Smoking and Alcohol

Law and Hackshaw's 1997 analysis found that smoking-related differences in BMD and hip-fracture risk varied with age and menopause status. It did not report a single 25% fracture-risk increase that applies to all smokers. [19]

Kanis and colleagues' pooled alcohol analysis found increased fracture risk with intake above two units daily. FRAX uses a separate input of three or more units daily. These thresholds describe the study and tool, rather than a universal BMD-loss percentage. [5,20]

Normal DEXA Bone Density Ranges and How to Read Your Report

Read the measured sites, BMD in g/cm², relevant T- or Z-score, and any technical limitations. A report's category is useful only when the correct score and diagnostic population are used. [1,3]

Reading the Spine Section

The spine report usually includes L1-L4. Structural abnormalities or artifacts can require exclusion of a vertebra. ISCD also allows exclusion where a vertebra differs by more than 1.0 in T-score from adjacent vertebrae. The remaining evaluable vertebrae determine the spine result; a single remaining vertebra should not be used for diagnosis. [1]

Reading the Hip Section

The total hip and femoral neck can each support diagnosis; use the lower eligible T-score. FRAX uses femoral-neck BMD. Monitoring may use the spine or hip, with the choice and LSC determined by scan quality and the facility's measurements. [1,3]

Forearm Measurements

The one-third radius can be useful when the hip or spine cannot be measured or interpreted, in hyperparathyroidism, or when body weight exceeds the DXA table limit. ISCD specifies the non-dominant one-third radius for diagnostic forearm measurement. [1]

A practical way to organize your report is:

Step 1. Identify the valid measured sites and whether T-score or Z-score interpretation applies.

Step 2. Check for technical limitations and compare the result with fracture history and contributing conditions.

Step 3. Read the country-specific FRAX probabilities if calculated, noting whether femoral-neck BMD was included.

Step 4. For repeat scans, compare the measured change with the facility's LSC and the treatment or clinical context. [1,3,5]

When to Repeat Your DEXA Scan

ISCD calls for individualized timing based on age, baseline density, treatment and factors that can accelerate bone loss. The BHOF guide recommends a measurement one to two years after starting or changing osteoporosis therapy, followed by intervals appropriate to the clinical circumstances. Untreated low bone mass does not carry a universal two-to-five-year schedule. [1,3]

The FLEX trial randomized 1,099 women after about five years of alendronate treatment. Continuing therapy reduced clinically recognized vertebral fractures compared with stopping, while nonvertebral fracture risk did not differ significantly. A treatment interruption depends on fracture risk and prior treatment, rather than one scan value alone. [9]

Special Populations

Men

The Endocrine Society guideline recommends DXA in men aged 70 or older and men aged 50-69 with risk factors. ISCD applies T-score categories to men aged 50 or older; in younger men, BMD alone cannot establish osteoporosis. [1,6]

Premenopausal Women

Z-scores are generally preferred before menopause. A result below the expected range calls for interpretation with fracture history and contributing conditions. The menopausal-transition exception and younger-adult interpretation are described in the ISCD positions. [1]

Patients on GLP-1 Receptor Agonists

BMD findings depend on population, dose and weight change. A 2024 phase 2 trial randomized 64 adults at increased fracture risk to semaglutide 1 mg weekly or placebo for 52 weeks. The semaglutide group had lower spine and total-hip BMD and greater weight loss; femoral-neck BMD differences were not statistically significant. This small trial is not a tirzepatide study and does not establish a DXA schedule for everyone using weight-loss medicines. [21]

Patients on Testosterone or Estrogen Therapy

Testosterone can improve BMD in selected men with low testosterone, as measured in the trial above. The Menopause Society's 2022 statement recognizes prevention of bone loss and fractures as a benefit of hormone therapy. DXA decisions still depend on the person's bone-health indications rather than hormone use alone. [18,26]