Because bone loss and osteoporosis can progress without any obvious symptoms, you must have a bone mineral density test to find out whether you have low bone density, or osteoporosis. Bone mineral density tests use X-rays to determine the amount of bone minerals in a certain segment of bone, usually in the hip, forearm or spine. The test results indicate the degree to which your bone density falls below or above a healthy and normal bone density.
T-Score
The T-score indicates the degree to which your bone density falls below or above the bone density of a healthy 30-year-old adult, according to the National Osteoporosis Foundation. Lower numbers indicate lower bone density. Doctors use this score to determine whether or not you have osteoporosis. T-scores between +1 and -1 indicate normal bone density. T-scores between -1 and -2.5 indicate low bone density and a risk for osteoporosis. Doctors diagnose patients with T-scores of -2.5 and lower with osteoporosis. In most bone density tests, a difference of 1 point in the T-score indicates a 10 to 15 percent difference in bone density. Thus, a person with a T-score of -3.5 has a bone mineral density 10 to 15 percent lower than a person with a T-score of -2.5. Health care providers typically diagnose osteoporosis medication for people with T-scores of -2.5 and below.
Z-Score
The Z-score indicates the degree to which your bone density falls below or above the normal bone density in a person of your age and body type. This score can indicate a form of osteoporosis not associated with the natural process of aging. Because many postmenopausal women and men over the age of 50 experience bone loss, Z-scores may indicate normal bone density for people in these categories even when they have osteoporosis. Doctors use Z-scores to evaluate bone density in children, premenopausal women and young men. For people in these categories, Z-scores above -2.0 indicate normal bone density, according to the National Osteoporosis Foundation.
