 [ Symptoms ] at what age or point is the t score in bone density scans used instead of a z score [ Disease ] a z score compares your bone density to what is normal for someone your age while a z score alone is not used to diagnose osteoporosis in premenopausal women it can provide important information here are some tips to help you understand your z score *if your z score is above  2 0 your bone density is considered within the ranges expected for your age or normal according to the international society for clinical densitometry iscd for example a z score of 0 5  0 5 and  1 5 is considered normal for most premenopausal women *if your z score is  2 0 or lower your bone density is considered below the expected range examples are  2 1  2 3 and  2 5 if your z score is in this range your health care provider will consider your health history and possible causes of bone loss including secondary osteoporosis before making a diagnosis of osteoporosis *if your z score is normal but you have broken one or more bones from a minor injury your health care provider may diagnose you with osteoporosis because some people with normal bone density break bones easily as mentioned above a bone density test will also show a t score a t score compares bone density to what is normal in a healthy 30 year old adult