- 01A blood test cannot diagnose osteoporosis
Osteoporosis is diagnosed by bone density on a DEXA scan (a T-score of -2.5 or lower) or by a fragility fracture, not by any lab value. The calcium, vitamin D, and PTH on your report are there to find a treatable cause of bone loss and rule out conditions that mimic it, not to confirm or exclude the disease.
- 02It is silent until a bone breaks
There are no symptoms while bone is thinning. The first sign of osteoporosis is often a fracture of the hip, spine, or wrist, which is why screening by age and risk matters more than waiting for something to feel wrong.
Osteoporosis is a disease of low bone density: the bone becomes porous and fragile enough to break from a minor bump or fall. It is diagnosed by a bone density scan or by a fragility fracture, never by a blood test. The calcium, vitamin D, and parathyroid hormone on your report are there to find why bone is being lost, not to confirm the disease itself.
What to do next: if you are a woman 65 or older, or younger with risk factors, ask your clinician about a DEXA scan. If your report flags calcium, vitamin D, or PTH, ask whether it points to a cause of bone loss worth treating. And if you have broken a bone from a minor fall, get assessed promptly, because that fracture can diagnose osteoporosis on its own.
What is osteoporosis?
Bone is living tissue, constantly broken down and rebuilt. Osteoporosis, which means porous bone, is what happens when breakdown outpaces rebuilding for years and the bone loses both mineral density and internal structure. The result is a skeleton that looks normal from the outside but fractures under loads it used to handle. It is common: up to 1 in 2 women and up to 1 in 4 men aged 50 and older will break a bone because of osteoporosis in their remaining lifetime. 1
What are the symptoms of osteoporosis?
Osteoporosis has no symptoms. You cannot feel your bones thinning, and there is no ache, stiffness, or warning that tracks with bone loss. That is why it is called a silent disease: the first sign is frequently a broken bone. 1
Fractures from osteoporosis usually hit the hip, spine, or wrist, and spine (vertebral) fractures often pass unnoticed at the time, showing up later as lost height or a stooped posture. 1
Bone density is not fixed. Most people reach peak bone mass in their late twenties to early thirties, hold roughly steady, then lose bone slowly with age. In women, the drop in estrogen at menopause speeds up bone loss for several years, which is why postmenopausal women are the highest-risk group. 1
How is osteoporosis diagnosed?
Osteoporosis is diagnosed with a DEXA scan (dual-energy X-ray absorptiometry), the reference test for bone mineral density. 2 It is a short, painless scan, usually of the hip and lower spine, using a very low dose of X-rays, far less than a chest X-ray. It reports a T-score.
A T-score compares your bone density with the average peak density of a healthy 30-year-old, counted in standard deviations, a fixed statistical step size where each step below zero is a meaningful drop in bone density. A Z-score, by contrast, compares you with people your own age and sex, and clinicians prefer the Z-score in premenopausal women, men under 50, and children. 2
A DEXA scan tells you how much bone you have; blood bone markers tell you how fast it is changing. They answer different questions.
For how a DEXA scan works in detail, and how the T-score and Z-score are calculated, see bone markers explained.
Where a T-score falls (example)T-score (SD below young-adult peak)
What to do at each level depends on where you land. A normal score means routine screening on the usual schedule for your age and risk. Low bone mass (osteopenia) is a cue for a fracture-risk assessment such as FRAX and attention to modifiable causes. A score in the osteoporosis range calls for a clinician evaluation to find the cause and set a plan, and a fragility fracture makes the diagnosis at any score.
What causes osteoporosis, and who is at risk?
Osteoporosis develops when the normal balance between bone removal and bone rebuilding tips toward loss. Some of that is unavoidable aging; much of it is driven by specific, identifiable factors. 1
- Older age, and being postmenopausal (the loss of estrogen speeds bone loss)
- Female sex, low body weight, and a small frame
- A parent who broke a hip
- Long-term glucocorticoid (steroid) medicines such as prednisone
- Smoking and heavy alcohol use
- Low calcium or vitamin D intake, and low physical activity
- Medical conditions that speed bone loss: an overactive thyroid or overactive parathyroid glands 5, celiac disease and other causes of poor absorption, chronic kidney disease, and early menopause
Where the blood work fits
The blood tests on a bone-health panel do not diagnose osteoporosis. They answer a different question: is a specific, treatable problem speeding up bone loss, such as an overactive parathyroid, an overactive thyroid, low vitamin D, or kidney disease? Ordered as part of a broader bone health workup, they look for that secondary cause and flag conditions that can mimic osteoporosis. 1
| Blood test | What it checks | What an abnormal result can point to |
|---|---|---|
| Calcium (total) | Calcium in blood, corrected for albumin (a blood protein that carries calcium) | High calcium can signal an overactive parathyroid or another cause; read it with PTH |
| 25-OH vitamin D | Vitamin D status | Low vitamin D is a common, treatable driver of bone loss and of a high PTH |
| PTH (parathyroid hormone) | The hormone that controls blood calcium | High PTH with high calcium suggests primary hyperparathyroidism; high PTH with low or normal calcium often reflects vitamin D deficiency or kidney disease |
| TSH (thyroid) | Thyroid activity | An overactive thyroid speeds bone loss |
| Kidney and liver function | Organ function that shapes bone metabolism | Chronic kidney disease disturbs calcium, phosphate, and PTH |
In someone who feels well, a genuinely high calcium is an overactive parathyroid until proven otherwise.
Two of these tests only make sense as a pair. As the PTH page puts it, PTH means nothing on its own: read it next to a total calcium drawn at the same time, and the pair is the diagnosis. And when a high PTH shows up with normal calcium, the usual driver is low vitamin D, so 25-OH vitamin D is the next number to read. If your clinician treats a driver like low vitamin D, they will usually recheck the level after a few months to confirm it has corrected. 5
Who should be screened, and how often?
The US Preventive Services Task Force recommends bone density screening for all women 65 and older, and for postmenopausal women under 65 who are at increased fracture risk on a formal risk tool. 3
The USPSTF recommends screening for osteoporosis with bone measurement testing to prevent osteoporotic fractures in women 65 years and older.US Preventive Services Task Force, 2018
To decide whether a younger postmenopausal woman needs a scan, clinicians use a fracture-risk calculator. The most common is FRAX, which estimates your 10-year probability of a major osteoporotic fracture and of a hip fracture from risk factors such as age, weight, prior fracture, smoking, and steroid use, with or without a bone density result. 4
Link · University of SheffieldFRAX Fracture Risk Assessment ToolEstimate your 10-year risk of a major osteoporotic fracture and of a hip fracture from clinical risk factors.frax.shef.ac.ukA DEXA scan is a separate imaging order, not part of a blood draw. Coverage varies by plan; Medicare covers a screening bone density scan for eligible people at set intervals, and many insurers do the same when you meet screening criteria. How often a scan is repeated depends on your starting score and your risk, and your clinician sets the interval. There is no genetic test to screen your family for osteoporosis; a parent's hip fracture is itself the risk factor that should prompt your own assessment.
Link · BHOFBone Health & Osteoporosis FoundationPatient guides on prevention, screening, fracture risk, and living with osteoporosis.bonehealthandosteoporosis.org
Citations
- LeBoff MS, et al. The clinician's guide to prevention and treatment of osteoporosis (Bone Health & Osteoporosis Foundation). Osteoporos Int. 2022.
- International Society for Clinical Densitometry (ISCD), 2019 Official Positions (Adult).
- US Preventive Services Task Force. Screening for Osteoporosis to Prevent Fractures. JAMA. 2018;319(24):2521-2531.
- FRAX Fracture Risk Assessment Tool, University of Sheffield / WHO Collaborating Centre.
- Bilezikian JP, et al. Evaluation and Management of Primary Hyperparathyroidism: Guidelines from the Fifth International Workshop. J Bone Miner Res. 2022;37(11):2293-2314.
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.