Osteoporosis is diagnosed primarily through a bone density scan called a DXA, which measures how much mineral your bones contain and compares it to a healthy baseline. A score of -2.5 or lower on this test confirms osteoporosis. But the full diagnostic picture often involves more than a single scan. Your doctor may also use fracture history, blood tests, risk calculators, and imaging to determine both the severity of bone loss and what’s driving it.
The DXA Scan
The standard test for osteoporosis is a dual-energy X-ray absorptiometry scan, known as a DXA (sometimes written DEXA). You lie on your back on a padded table while a machine passes two low-energy X-ray beams through your body. One beam is absorbed by soft tissue, the other by bone. The difference between them lets the machine calculate your bone mineral density, measured in grams per square centimeter.
The scan typically measures two sites: the lumbar spine (lower back) and the hip. These areas are evaluated because they’re common fracture sites and give a reliable picture of overall skeletal health. The entire process takes about 10 minutes, requires no injections or special preparation, and exposes you to very little radiation, far less than a standard chest X-ray.
What Your T-Score Means
Your DXA results come back as a T-score, which compares your bone density to that of a healthy 30-year-old adult at peak bone mass. The World Health Organization uses these cutoffs:
- -1.0 or higher: Normal, healthy bone density.
- -1.0 to -2.5: Osteopenia, meaning bone density is below normal but not yet in the osteoporosis range.
- -2.5 or lower: Osteoporosis.
Each full point on the T-score scale represents a meaningful increase in fracture risk. Someone with a T-score of -3.0 has substantially thinner bones than someone at -2.0, even though both numbers might look similar at a glance. The score that matters most for predicting hip fractures is typically the one taken at the femoral neck, the narrow section connecting the ball of your hip joint to the thighbone.
Who Should Get Screened
The U.S. Preventive Services Task Force recommends routine bone density screening for all women aged 65 and older. Postmenopausal women younger than 65 should also be screened if they have risk factors that raise their fracture probability, such as low body weight, smoking, a parent who fractured a hip, or long-term steroid use. These guidelines apply to adults without a known history of fragility fractures or conditions already linked to bone loss.
For men, there is no universal screening recommendation. The evidence on when and whether to routinely screen men hasn’t been strong enough to establish a clear guideline, so screening decisions for men are typically made case by case based on individual risk factors like chronic steroid therapy, low testosterone, or heavy alcohol use.
Diagnosis Without a DXA Scan
In some cases, osteoporosis can be diagnosed clinically, without waiting for a bone density scan. If you’ve had a fragility fracture (a bone break caused by a fall from standing height or less, or even by something as minor as coughing or bending over), that alone can be enough for a diagnosis. A broken wrist from catching yourself during a fall, a hip fracture from a low-impact stumble, or a vertebral compression fracture discovered incidentally on an X-ray all qualify.
Certain high-risk situations also justify starting treatment without a DXA. People taking glucocorticoid medications (like prednisone at doses equivalent to 5 mg or more per day), men on hormonal therapy for prostate cancer, and women on hormonal therapy for breast cancer face such elevated fracture risk that their doctors may proceed directly to treatment.
The FRAX Risk Calculator
A T-score alone doesn’t capture every factor that contributes to fracture risk. That’s where the FRAX tool comes in. Developed by the World Health Organization, FRAX uses your age, sex, weight, smoking status, alcohol intake, fracture history, family history of hip fracture, and other clinical factors to estimate your 10-year probability of breaking a hip or having another major osteoporotic fracture.
FRAX is especially useful for people with osteopenia, the gray zone between normal bone density and osteoporosis. Current guidelines from the Bone Health and Osteoporosis Foundation recommend considering treatment for people with osteopenia whose FRAX results show a 10-year major fracture probability of 20% or higher, or a hip fracture probability of 3% or higher. Your DXA results can be entered into the FRAX calculator to refine the estimate, but FRAX can also generate a rough prediction without a DXA score.
Blood Tests to Find the Underlying Cause
Once low bone density is identified, your doctor will likely order blood work to check whether something other than aging is causing or accelerating bone loss. This matters because treating the underlying condition can sometimes slow or stop the process more effectively than treating the bone loss alone.
A standard workup includes:
- Calcium and albumin: Abnormal calcium levels can point to parathyroid problems, one of the more common treatable causes of bone loss.
- Vitamin D: Measured as 25-hydroxy vitamin D in your blood, this shows whether your body has the raw materials it needs to absorb calcium and maintain bone.
- Kidney function (creatinine and GFR): Kidney disease directly affects bone health by disrupting how your body processes minerals.
- Thyroid function: An overactive thyroid speeds up bone breakdown.
- Testosterone (in men): Low testosterone is a significant contributor to bone loss in men and is easily screened with a blood draw.
If your doctor suspects a rarer cause, such as celiac disease, Cushing’s syndrome, or other conditions that interfere with nutrient absorption or hormone balance, more specialized tests may follow. But for most people, the initial panel covers the likely culprits.
Bone Turnover Markers
A newer layer of diagnostic information comes from blood tests that measure how actively your bones are being broken down and rebuilt. These are called bone turnover markers. The two reference standards recommended by the International Osteoporosis Foundation are PINP, which reflects bone formation, and beta-CTX, which reflects bone breakdown.
These markers don’t replace a DXA scan, but they add information that density alone can’t provide. Research shows that high levels of bone turnover predict fracture risk independently of bone mineral density, meaning someone with a borderline T-score but very active bone breakdown may be at higher risk than their DXA result alone suggests. These tests are also useful for tracking whether treatment is working, since changes in turnover markers show up in blood work months before changes in bone density appear on a repeat DXA.
Vertebral Fracture Assessment
Many spinal fractures from osteoporosis happen silently, without sudden pain or an obvious injury. You might notice you’ve gotten shorter, or that your upper back has developed more of a curve, but the fracture itself often goes undetected unless someone looks for it. A Vertebral Fracture Assessment (VFA) is a low-dose imaging scan that can be done on the same DXA machine during your bone density appointment.
An international working group on DXA best practices has recommended that VFA ideally be performed in all patients getting a bone density scan. In practice, it’s most commonly ordered for people with a T-score below -1.0 who also have additional risk factors: oral steroid use, a prior vertebral fracture, noticeable height loss, or advanced age. Finding even one previously unknown spinal fracture can change your diagnosis and treatment plan significantly, since a prior vertebral fracture is one of the strongest predictors of future fractures.
Trabecular Bone Score
Standard DXA scans measure how much bone you have, but not how well that bone is structured. The Trabecular Bone Score (TBS) fills that gap. It’s a software analysis applied to the same spine image captured during your DXA, so it requires no additional scanning. TBS evaluates the texture and microarchitecture of your bone, providing information about skeletal quality that’s partially independent of density.
This matters because two people with identical T-scores can have very different fracture risks depending on how their bone tissue is organized. TBS has been validated as a fracture prediction tool and can be incorporated into FRAX calculations to improve their accuracy. Not every DXA facility offers TBS, but it’s becoming more widely available and is particularly helpful for people whose T-scores fall in the borderline range.