Normal bone density is reported with a T-score of -1.0 or above and a Z-score greater than -2, according to MedlinePlus. T-scores less than -1.0 and Z-scores less than -2.0 may indicate abnormal bone loss and the potential for subsequent fractures.
These standards of measurement compare the results of an individual's bone density scan with what is considered average for their particular age, race and gender. T-scores and Z-scores are most commonly measured through the use of a dual-energy x-ray absorptiometry, or DEXA, scan, explains MedlinePlus. The central DEXA scan measures bone density in the hips and lower spine and provides the most thorough indicator of bone loss. The peripheral DEXA scan measures density in smaller, more localized regions, including a finger, wrist or heel, and can be performed in doctor's offices or pharmacies.