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©2013 UpToDate ® Print Email Definitions of normal bone density, osteopenia, and osteoporosis T-score Bone density +1 to -1 Normal bone density Bone density that is between 0 and 1 standard deviation below the mean is considered to be normal. This may be reported as a T-score of +1 to -1. Treatment is not usually recommended for people with normal bone density, although preventive measures (eg, calcium supplements, weight-bearing exercise) are recommended to prevent osteopenia and osteoporosis. 1 to -2.4 Osteopenia Bone density that is between 1 and 2.5 standard deviations below the mean is called osteopenia. This may be reported as a T-score of -1 to -2.4. A person with osteopenia does not yet have osteoporosis, but is at risk of developing it if not treated. -2.5 or less Osteoporosis Osteoporosis is defined as BMD more than 2.5 standard deviations (SD) below the mean of normal young women. This is reported as a T-score of -2.5 or less. The lower the bone density, the greater the risk of fracture. The World Health Organization (WHO) has defined normal bone density as a value within one standard deviation (SD) from average peak bone mass. Standard deviation is a statistical measure that defines how much a patient's result varies from the "average" young adult.