Bone Density T-Score and Z-Score: Charts by Age and What Your Numbers Mean

A T-score compares your bone mineral density to the average for a healthy 30-year-old of the same sex. A T-score of 0 means your bone density equals the young adult average. Each -1.0 increment means your density is one standard deviation below that average — roughly 10-12% lower. T-scores above -1.0 are normal, -1.0 to -2.5 indicate osteopenia, and below -2.5 indicate osteoporosis.

A T-score above -1.0 is considered normal. Ideally, T-scores close to 0 indicate bone density near peak levels. A T-score between 0 and +1.0 is excellent. After menopause, maintaining a T-score above -1.0 is the goal — this requires active intervention (exercise, nutrition, and possibly hormone therapy) since the natural trajectory is downward.

A Z-score compares your bone density to the average for people of your same age and sex, rather than to young adult peak (which is what the T-score does). A Z-score of 0 means your bone density is average for your age. A Z-score below -2.0 means your bone density is significantly lower than expected for your age, suggesting an additional cause of bone loss beyond normal aging that should be investigated.

Average T-scores decline with age in women: age 40 (-0.2 to -0.5), age 50 (-0.5 to -1.0), age 55 (-1.0 to -1.5), age 60 (-1.2 to -1.8), age 65 (-1.5 to -2.2), age 70 (-1.8 to -2.5), age 80 (-2.0 to -3.0). The sharpest decline occurs between ages 50-60 during the menopausal transition, when 2-3% of bone density is lost annually due to estrogen withdrawal.