National Osteoporosis Foundation recommends treatment for patients over age 50 based on the following:
Presence of a hip or vertebral (symptomatic or mophometric) fracture
T score <-2.5 at the spine of femoral neck
T score -2.5 to -1.5 (osteopenia) with a 10 year probability of hip fracture >= 3% or major osteoporotic fracture >= 20% based on the US adapted FRAX algorithym.
Clinician or patient judgement.