The diagnostic criteria of osteoporosis are based on the T-value in the dual energy X-ray bone density test, which indicates how many standard deviations (SD) the measured bone density value differs from the average bone density of normal young people of the same sex. When your T value is less than or equal to -2.5, it means you have osteoporosis; when your T value is less than or equal to -2.5 and accompanied by more than one fracture, it means you already have severe osteoporosis. Bone densitometry can be used to find out whether the bone mass has decreased? Is it severe in degree? It can be used as a basis for early prevention and treatment of osteoporosis. Regular bone density check can understand the rate of bone loss and determine the effectiveness of prevention and treatment. It can also be used as a basis for determining the risk of osteoporotic fracture. 12% or less bone loss, low risk of fracture; 12%-30% bone loss, low to medium risk of fracture;; greater than 30% bone loss, medium to high risk of fracture. Treatment should be sought to prevent fracture; bone loss greater than 30% with one or more fractures is considered severe osteoporosis and the risk of fracture is extremely high (or suffering from fracture) and should be actively treated to prevent further fractures.