Z-score interpretation

A Z-score compares your bone density to other people your own age, sex, and often ethnicity. It's different from a T-score, which compares you to a healthy young adult. Z-scores are especially useful in younger people, children, and premenopausal women, where T-scores aren't the standard tool for diagnosing osteoporosis.

A Z-score around 0 means your bone density is typical for your age group. A Z-score of -2.0 or lower is generally considered 'below the expected range for age' and may prompt your doctor to look for an underlying cause of bone loss, such as a hormone problem, medication side effect, or digestive condition. A positive Z-score means your bones are denser than average for your age.

On its own, a Z-score doesn't diagnose osteoporosis in older adults, that's based on the T-score. But a low Z-score at any age is a signal worth discussing with your doctor, since it can point toward a secondary cause of bone loss rather than just normal aging. Your doctor can help interpret the number alongside your full health picture.