You often don't know you have osteoporosis until a bone breaks
Osteoporosis causes bones to become thinner and more fragile, but you cannot feel it happening. There are no symptoms—no pain, no warning signs—until a bone fractures from a minor fall or even a bump. Many people discover they have osteoporosis only after breaking a hip, spine, or wrist, or after a doctor orders a bone density test for another reason.
The only way to know for certain whether you have osteoporosis is through a bone density scan called a DEXA scan (dual-energy X-ray absorptiometry). This test measures how much mineral is packed into your bones and compares the result to a healthy young adult's bones. The scan itself takes about 10 to 30 minutes, uses very little radiation, and is painless.
Key Takeaways
- A DEXA scan is the only test that can diagnose osteoporosis; you cannot know you have it from symptoms alone.
- The scan produces a T-score that tells you how your bone density compares to a healthy young adult's bones.
- A T-score of -2.5 or lower means osteoporosis; between -1 and -2.5 means low bone mass (sometimes called osteopenia).
- Your doctor may recommend screening if you are over 50, have had a fracture, or have risk factors like family history or certain medications.
- Fractures from minor trauma—a fall from standing height or less—are often the first sign that bone density has dropped.
What a DEXA scan measures and how to read the results
The DEXA scan measures bone mineral density at your hip, spine, and sometimes forearm. The machine sends two X-ray beams through the bone; the difference in how much radiation each beam absorbs tells the technician how dense the bone is. The result is reported as a T-score.
The T-score compares your bone density to the average bone density of a healthy 30-year-old woman (the standard reference, regardless of your sex). A T-score of 0 means your bones are exactly as dense as that reference. Negative numbers mean your bones are less dense. The more negative the number, the thinner your bones are.
Here is what the T-score ranges mean:
| T-Score Range | What It Means |
|---|---|
| -1 and above | Normal bone density |
| -1 to -2.5 | Low bone mass (sometimes called osteopenia) |
| -2.5 and below | Osteoporosis |
| -2.5 and below, plus a fracture | Severe osteoporosis |
The score is not a prediction of whether you will break a bone—it is a snapshot of bone density at the moment of the scan. Two people with the same T-score may have different fracture risk depending on age, sex, and other factors.
Who should get a DEXA scan and when
The U.S. Preventive Services Task Force recommends bone density screening for all women age 65 and older, and for postmenopausal women under 65 who have risk factors. For men, the recommendation is less clear; many doctors screen men age 70 and older, or younger men with risk factors.
Risk factors that may prompt earlier screening include a parent or sibling with osteoporosis or a hip fracture, a personal history of fracture after age 50, use of corticosteroid medications for three months or longer, rheumatoid arthritis, or conditions that affect how your body absorbs calcium (such as celiac disease or inflammatory bowel disease). Smoking and heavy alcohol use also increase risk.
If you have already had a fracture from a minor fall or bump, your doctor will likely order a DEXA scan without waiting for age-based screening guidelines. A fracture in someone under 50 is unusual enough that doctors investigate bone density as a possible cause.
What happens between the scan and your results
After the DEXA scan, a radiologist reviews the images and calculates your T-score. The results are usually ready within a few days. Your doctor will receive the report and contact you to discuss what the score means for your health and whether treatment is needed.
If your T-score shows low bone mass or osteoporosis, your doctor may also calculate your 10-year fracture risk using a tool called FRAX (Fracture Risk Assessment Tool). FRAX combines your T-score with other factors—age, sex, weight, smoking status, alcohol use, and whether you have had a fracture—to estimate your risk of breaking a hip or another major bone in the next decade. This helps your doctor decide whether medication is necessary or whether lifestyle changes alone are enough.
Fractures that suggest osteoporosis even without a scan
Certain fractures are red flags for osteoporosis, even in people who have not had a bone density test. A fracture of the hip, spine, or wrist from a fall from standing height or less—or from a cough, sneeze, or minor bump—suggests that bone density is lower than normal. These are called fragility fractures.
If you have had a fragility fracture, your doctor will order a DEXA scan to confirm osteoporosis and assess your fracture risk. Even if the scan shows only low bone mass rather than osteoporosis, a history of fragility fracture changes the treatment recommendation, because the fracture itself proves your bones are weaker than expected.
Spine fractures are sometimes discovered by accident on X-rays or CT scans done for other reasons. A compressed or collapsed vertebra visible on imaging is often a sign of osteoporosis, even if you did not remember having a fall or injury that caused it. Some spine fractures cause no pain or symptoms.
Why you might have osteoporosis and not know it
Bone is living tissue that is constantly being broken down and rebuilt. In younger years, new bone is added faster than old bone is removed, so bone mass increases. Most people reach peak bone mass around age 30. After that, bone remodeling continues, but more bone is lost than gained.
In women, bone loss accelerates sharply after menopause, when estrogen levels drop. Estrogen helps bones retain calcium. Men lose bone more slowly and usually later in life, but the process is the same. By the time you feel weak or notice a change in your posture, significant bone loss has already occurred.
Certain medications and conditions speed up bone loss. Corticosteroids (used for asthma, rheumatoid arthritis, and other inflammatory conditions) are among the strongest risk factors. Thyroid hormone replacement, some cancer treatments, and certain seizure medications also increase bone loss. Conditions that affect calcium absorption—celiac disease, Crohn's disease, cystic fibrosis—raise risk even in younger people.
What to do if your DEXA scan shows low bone density
A low T-score does not automatically mean you need medication. Your doctor will consider your age, sex, fracture history, and 10-year fracture risk before recommending treatment. If your risk is low, your doctor may suggest lifestyle changes: weight-bearing exercise (walking, jogging, dancing), strength training, adequate calcium and vitamin D intake, and avoiding smoking and excess alcohol.
If your fracture risk is moderate to high, or if you have already had a fragility fracture, your doctor may prescribe medication. The most common first-line drugs are bisphosphonates (such as alendronate or risedronate), which slow bone loss. Other options include denosumab, hormone-related therapy, or newer medications depending on your situation.
Even if you start medication, lifestyle changes remain important. Exercise and adequate nutrition support bone health and reduce fall risk, which is just as important as bone density in preventing fractures.
Frequently Asked Questions
Can osteoporosis run in families?
Yes. If a parent or sibling has osteoporosis or has had a hip fracture, your risk is higher. Genetics influence how much peak bone mass you reach and how quickly you lose bone. Family history alone does not mean you will develop osteoporosis, but it is a reason to talk to your doctor about screening.
Does a DEXA scan hurt or expose you to dangerous radiation?
No to both. The scan is painless—you lie on a table while the machine passes over you. The radiation dose is very low, about one-tenth of a standard chest X-ray. The benefit of knowing your bone density far outweighs the small radiation risk.
What if my T-score is between -1 and -2.5?
This range is called low bone mass or osteopenia. It means your bones are thinner than normal but not yet in the osteoporosis range. Your doctor will assess your fracture risk and may recommend exercise, calcium and vitamin D, and monitoring with another scan in one to two years. Medication is not always necessary at this stage unless your risk is high.
How often should I get a DEXA scan?
If your bone density is normal, screening every 10 years is usually sufficient for women over 65 and men over 70. If you have low bone mass or osteoporosis, your doctor may recommend repeat scans every one to two years to monitor whether treatment is working or bone loss is continuing.
Can you reverse osteoporosis?
Medication and lifestyle changes can slow bone loss and sometimes increase bone density slightly, but osteoporosis cannot be completely reversed. The goal is to stop further bone loss, maintain the bone you have, and reduce fracture risk through exercise, nutrition, and medication if needed.