Diagnostic category	Criterion
Normal bone mass	BMD within 1 standard deviation of the reference mean for young adults (T-score ≥ −1.0)
Low bone mass (osteopenia)	BMD of > 1.0 to < 2.5 standard deviations below the mean for young adults (T-score < −1.0 and > −2.5)
Osteoporosis	BMD ≥ 2.5 standard deviations below the mean for young adults (T-score ≤ −2.5)
Severe or established osteoporosis	BMD ≥ 2.5 standard deviations below the mean for young adults in the presence of one or more fractures