What is the range for normal bone density levels in people over 50?

Normal bone density for people 50 years old and older is within 1 standard deviation, or SD, of the peak bone density of a 30-year-old adult, a measurement called the young adult mean, notes the National Institutes of Health. Greater readings indicate bone loss or osteoporosis.

Bone density between 1 and 2.5 SD below the young adult mean indicates low bone mass, which increases the risk of developing osteoporosis, reports the National Institutes of Health. Bone density of 2.5 SD or more below the young adult mean indicates the presence of osteoporosis. Bone density of 2.5 SD or more below the young adult mean with a history of one or more osteoporosis-related fractures indicates severe osteoporosis.