Table 5.

Defining osteoporosis by BMD

WHO definition of osteoporosis based on BMD
Classification	BMD	T-score
Normal	Within 1 SD of the mean level for a young-adult reference population	T-score at −1.0 and above
Low bone mass (osteopenia)	Between 1.0 and 2.5 SD below that of the mean level for a young-adult reference population	T-score between −1.0 and −2.5
Osteoporosis	2.5 SD or more below that of the mean level for a young-adult reference population	T-score at or below −2.5
Severe or established osteoporosis	2.5 SD or more below that of the mean level for a young-adult reference population with fractures	T-score at or below −2.5 with one or more fractures

Although these definitions are necessary to establish the presence of osteoporosis, they should not be used as the sole determinant of treatment decisions