Osteopenia vs. Osteoporosis
| Osteopenia (low bone mass) | Osteoporosis | |
|---|---|---|
| What it is | A reduction in bone mineral density below normal reference values that does not meet the criteria for osteoporosis (StatPearls, NIH, 2025) | A bone disease in which bone mineral density and mass fall, or bone structure and strength change, increasing fracture risk (NIAMS, NIH) |
| The number | T-score between -1.0 and -2.4 (MedlinePlus, July 8, 2024); the World Health Organization definition is cited as -1.0 to -2.5 (StatPearls, NIH, 2025). A T-score is a standard-deviation score, not a lab value in mg/dL | T-score of -2.5 or less (MedlinePlus, July 8, 2024) |
| What causes it | Bone loss outpacing bone rebuilding after peak bone mass, reached by about the third decade of life (StatPearls, NIH, 2025). Risk rises with age, female sex, thin or small-boned build, and race, with white and Asian women at highest risk (NIAMS, NIH) | The same processes and risk factors, further along; it is the major cause of fractures in postmenopausal women and older men (NIAMS, NIH) |
| How it's diagnosed | Dual-energy x-ray absorptiometry (DXA) — a low-dose scan, usually of hip and spine (NIAMS, NIH) | The same DXA scan; hip and spine DXA is generally considered the most reliable way to diagnose osteoporosis and predict fracture risk (NIAMS, NIH) |
| Which score is used | T-score (your density vs. a healthy young adult of your sex) if you are a postmenopausal woman or a man 50 or older; Z-score (vs. others your age, weight, sex, and ethnic origin) if you are premenopausal, a man under 50, or a child (MedlinePlus, July 8, 2024) | Same rule — the score used depends on your age and sex, not on how low the result is |
| Symptoms | Most people have none until a fracture occurs, often after minimal trauma (StatPearls, NIH, 2025) | Often called a "silent" disease; many people have no symptoms until a bone breaks (NIAMS, NIH) |
| How it's typically treated | Nutrition, exercise, and fall prevention; medication is recommended when the 10-year probability of hip or major osteoporotic fracture estimated by the Fracture Risk Assessment Tool (FRAX) is high, while low-to-moderate risk is approached differently (StatPearls, NIH, 2025) | Same goals — slow or stop bone loss and prevent fractures — through nutrition, lifestyle, exercise, fall prevention, and medication (NIAMS, NIH). FDA-approved options include bisphosphonates such as alendronate (Fosamax) and calcitonin (Miacalcin) |
| Follow-up | Repeat DXA can detect low bone density before osteoporosis develops and help predict fracture risk (NIAMS, NIH) | Repeat DXA can also monitor whether ongoing treatment is working (NIAMS, NIH) |
For either result, get same-day medical contact for sudden severe back pain after a minor fall, lift, or cough, or if you cannot put weight on a hip after a fall. Go to an emergency department for new leg numbness or weakness, or loss of bladder or bowel control, with back pain.
