A T-score within 1 SD (+1 or -1) of the young adult mean indicates normal bone density. A T-score of 1 to 2.5 SD below the young adult mean (-1 to -2.5 SD) indicates low bone mass. A T-score of 2.5 SD or more below the young adult mean (more than -2.5 SD) indicates the presence of osteoporosis.