A T-score indicates the number of standard deviations (SD) a patient's bone mineral density (BMD) is above or below the mean BMD of a healthy young-adult reference population of the same sex.

Who should be evaluated using T-scores?

Per ISCD and NIAMS guidance, WHO T-score diagnostic criteria apply specifically to postmenopausal women and men aged 50 and older. For premenopausal women, men under 50, and children, Z-scores (comparison to age-matched peers) are recommended.

What are the WHO T-score thresholds?

Normal bone mass is a T-score of -1.0 or higher. Low bone mass (osteopenia) is between -1.0 and -2.5. Osteoporosis range is -2.5 or lower.

Which anatomical scan sites are valid for WHO diagnosis?

ISCD identifies the lumbar spine (L1-L4), total hip, and femoral neck as standard diagnostic sites. The 33% (one-third) radius is used when hip or spine cannot be scanned or interpreted, or in primary hyperparathyroidism. Total-body and other forearm regions are not validated diagnostic sites.

Does a low T-score automatically equal high fracture risk?

No. While BMD correlates with bone strength, absolute fracture risk depends on age, prior fracture history, glucocorticoid use, parental hip fracture, and other clinical factors integrated via assessment tools like FRAX. T-score alone is not a complete diagnosis.

Bone Density T-Score Calculator

Enter a DXA scan T-score (-5.0 to +5.0) to evaluate WHO diagnostic category ranges for adult populations with clinical limitations.

Enter DXA T-Score Parameters

Educational reference for dual-energy X-ray absorptiometry (DXA) reports.

Population group *

DXA scan site *

Per ISCD, lumbar spine, total hip, and femoral neck are primary diagnostic regions.

T-Score value (SD) *

WHO Classification Boundaries

Classification Range	T-Score Threshold
Normal bone mass	≥ −1.0 SD
Low bone mass (Osteopenia)	−2.5 < T < −1.0 SD
Osteoporosis range	≤ −2.5 SD

Definitions & Diagnostic Scope

SD: Standard deviation from the young-adult reference mean; it is not a fixed percentage of BMD.
Reference: T-scores compare BMD against peak young-adult reference databases; Z-scores compare against age/sex-matched peers.
Privacy: The entered score is interpreted locally and is masked from session-replay capture.

Ready for Interpretation

Select population, DXA site, and enter a T-score to view classification.

Summary

Enter a DXA scan T-score (-5.0 to +5.0) to evaluate WHO diagnostic category ranges for adult populations with clinical limitations.

How it works

Select the evaluated population group (WHO T-score criteria apply to postmenopausal women and men age 50+).
Select the validated DXA anatomical site (lumbar spine, total hip, femoral neck, or 33% radius).
Enter the reported T-score between -5.0 and +5.0.
View the classification range: Normal (>= -1.0), Low bone mass / Osteopenia (-2.5 < T < -1.0), or Osteoporosis range (<= -2.5).
Review diagnostic boundaries, unit definitions, and clinical limitations.

Use cases

Review DXA report T-scores before clinician follow-up consultations.
Verify WHO diagnostic boundary thresholds (-1.0 and -2.5 standard deviations).
Check population applicability (T-score vs. Z-score indications per ISCD/NIAMS).
Educational reference for healthcare students evaluating bone densitometry reports.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu