A DEXA scan (dual-energy X-ray absorptiometry) measures bone mineral density (BMD) in specific areas — usually the lumbar spine and hip. The result is expressed as a T-score, a Z-score, or both. Understanding these numbers is the key to understanding your fracture risk.
What T-scores mean
The T-score compares your bone density to that of a healthy young adult of the same sex at peak bone density. A score of 0 is average; each unit below 0 represents one standard deviation below the reference.
- T-score of 0 to −1.0 — normal bone density
- T-score of −1.0 to −2.5 — osteopaenia (low bone density); increased fracture risk but not yet osteoporosis
- T-score below −2.5 — osteoporosis; significantly elevated fracture risk
- T-score below −2.5 with a fragility fracture — severe osteoporosis
Z-scores and what they add
The Z-score compares your density to others of your age and sex. A very low Z-score in a young person suggests something beyond normal age-related bone loss — perhaps a secondary cause such as coeliac disease, malabsorption or steroid use. This is why Z-scores are used rather than T-scores in premenopausal women, men under 50 and children.
What happens next
Osteopaenia doesn't automatically require medication. Your doctor will calculate your FRAX score — a 10-year fracture probability tool — and take into account risk factors including age, smoking, alcohol, steroid use, fall risk and family history of fracture. Treatment might range from calcium and vitamin D supplementation to bisphosphonate therapy depending on overall risk.