How Osteoporosis Is Diagnosed

DEXA Imaging is Key

Female doctor showing an x-ray on the tablet

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Osteoporosis is a common health condition, particularly in older women. Fractures related to osteoporosis cause significant pain, disability, and sometimes even death. But unless your osteoporosis is severe, you won’t have any major signs of it on a clinical exam. Because of this, it’s important that people at risk of osteoporosis undergo regular screenings for the condition, via dual-energy X-ray absorptiometry (DEXA) assessment. Unfortunately, many people currently at risk of osteoporosis and fracture aren’t regularly screened for osteoporosis and don’t receive the treatments that they need.

Osteoporosis Screening

Osteoporosis is diagnosed with a combination of factors, which include your medical history, exam, and lab and imaging tests. Many people have osteoporosis without having any signs or symptoms at all. However, a person might have symptoms like height loss or stooped posture.

People with osteoporosis are also more likely to get fractures from what would be only minor injuries in someone without it. That’s sometimes why a person is first evaluated for osteoporosis.

Because osteoporosis can only be diagnosed with a bone density test, it’s important that people at risk of osteoporosis get regular screenings for the disease.

You can get an idea of your potential risk with the quiz provided by the International Osteoporosis Foundation.

In addition to diagnosing osteoporosis, your clinician will need to diagnose its underlying cause. Most commonly, the cause is “primary osteoporosis,” thought to be caused by aging and changes in sex hormones.

Sometimes osteoporosis is caused by another medical condition, or even by a medication used to treat another condition. That’s called “secondary osteoporosis." That’s one reason your clinician needs to know about your other medical conditions for proper diagnosis.

Imaging

The preferred mode for assessing osteoporosis is a dual-energy X-ray absorptiometry (DEXA or DXA) assessment of the hip and lumbar (lower) spine. This is sometimes also called “central” DEXA to distinguish it from DEXA performed on other areas of the body.

This test is the best and most reliable one, if it is available. It is a painless and noninvasive test.

DEXA is a type of bone density scan, which can show if osteoporosis has made your bones less dense and more likely to fracture. DEXA can also be used to track how your osteoporosis responds to treatment over time and can be helpful in assessing your risk of fracture.

A DEXA uses a specialized type of X-ray to get images of your bones, though it gives much more detailed information about your bones than a standard X-ray. DEXA uses a low dose of ionizing radiation, much lower than that used in a CT scan for example.

The test requires very little to no preparation. You’ll need to lie very still for a moment while the technician gets the DEXA images. A radiologist will interpret the scans.

The U.S. Preventive Services Task Force recommends that all women over the age of 65 be screened for osteoporosis via DEXA.

You also might need a DEXA if you have certain risk factors for osteoporosis or signs that you might have it. Some of these include:

  • Having a fracture from slight trauma at age 50 or older
  • Height loss
  • History of smoking
  • Long-term use of glucocorticoid therapy
  • History of alcohol abuse
  • Diet deficient in calcium or vitamin D

Even if your DEXA shows that you don’t have osteoporosis now, you might need another scan in the future.

T-Scores and Z-Scores

Usually, your DEXA test results will provide two scores.

The T-score gives an idea of the amount of bone mass you have compared to a young adult of the same gender. A score of -1 or higher is considered normal. A score between -1.1 and -2.4 is classified as osteopenia (low bone mass that isn’t yet osteoporosis). A person with a T score of -2.5 or lower has even less bone mass. They are diagnosed with osteoporosis.

A Z-score is also usually provided. This number gives information about how your bone mass compares to people of the same age, size, and gender. Z-scores of -2.0 or less is considered below the expected range. Z-scores are particularly important in evaluating children and younger adults.

Other Screening Tests

A DEXA of the lower spine and hips provides the definitive diagnosis of osteoporosis, but there are other tests that can sometimes be used to screen for the disease. They assess bone density in an area away from the central spine, like the forearm, wrist, or heel. These imaging tests use X-rays (like in CTs) or ultrasound.

These tests aren’t as accurate as a DEXA of the lower back. They are sometimes available at health fairs or at some medical offices. These include:

  • Peripheral DEXA (pDXA)
  • Quantitative ultrasound (QUS)
  • Certain kinds of CT scans (Peripheral quantitative computed tomography, or pQCT) 

These tests can be helpful if DEXA testing of the spine and hips is not available. If you get one of these other tests done, be sure to follow-up with your health care provider. You might need a DEXA of the spine and hips for a definitive diagnosis.

These other imaging tests can also be helpful in people of larger size since some DEXA machines cannot evaluate people over 300 pounds.

Other Imaging Tests to Evaluate Bone Fracture

If there is a concern that you might have a bone fracture due to your osteoporosis, you might need additional imaging tests. These might include:

  • Bone X-ray of the spine
  • CT scan of the spine
  • MRI of the spine

These tests can give an idea if you have any fractures caused by your osteoporosis.

X-rays or additional imaging can also be helpful if your doctor is concerned that underlying cancer or other condition might have contributed to a bone break.

Labs and Tests

Imaging tests play the leading role in diagnosis, but laboratory tests are sometimes important as well. These are used primarily to detect or rule out causes of osteoporosis that are not related to aging and instead caused by another health condition.

You are likely to need some labs if your doctor has diagnosed you with osteoporosis based on DEXA imaging or another type of imaging. These tests can also give your physician an idea about whether certain medications for osteoporosis would not be safe for you. Some of these tests might include:

  • Vitamin D (for vitamin D deficiency)
  • Calcium (for calcium deficiency)
  • Creatinine (or other tests for kidney disease)
  • Thyroid-stimulating hormone (for thyroid disease)
  • Tests of liver function
  • Complete blood count (CBC) (for conditions like anemia or multiple myeloma)

These can give an idea of whether you might have another medical condition that is causing your osteoporosis, like thyroid disease.

It’s estimated that up to up to 30% of cases of osteoporosis in women post-menopause are caused by another medical condition and not just from osteoporosis due to age. This percentage is higher in men and pre-menopausal women.

Differential Diagnosis

For a person coming to the doctor for a bone break for minor trauma, it’s especially important to evaluate for potential causes that are not directly related to osteoporosis. For example, someone might have such a bone break from underlying bone cancer or from cancer that has spread from somewhere else in the body. Multiple myeloma (a blood cancer) also might result in such a break.

It’s important that healthcare providers seek out these potential underlying causes. That’s why it’s so important that they get a total picture of your health, including your medication history and symptoms that might appear unrelated.

The specific diagnosis of secondary osteoporosis can be quite complicated since it has many potential diverse and rare causes originating in different systems of the body. Depending on the additional clues present, you might need other tests to help figure out what is going on.

For example, this might include tests for celiac disease, for certain hormones (like parathyroid hormone or cortisol), for HIV antibodies, or even genetic testing for certain rare diseases. Sometimes a person might have one of these secondary causes that are serving to worsen osteoporosis that is already present.

You are more likely to need additional lab tests if your medical picture isn’t consistent with primary osteoporosis.

For example, pre-menopausal women and men of any age might be more likely to need additional tests, as would any children with osteoporosis. You are also more likely to need such tests if your imaging shows exceptionally low bone density, or if you haven’t responded to previous treatment for osteoporosis.

Don’t hesitate to ask your doctor about whether your osteoporosis might be caused by another medical condition. It doesn’t hurt to do a little investigation just in case.

Evaluating Fracture Risk

The potential for bone breaks is such a key consideration in osteoporosis. Because of this, before you plan your treatment, it may be helpful for you and your doctor to get a sense of your risk.

The Fracture Risk Assessment Tool (FRAX) is an online algorithm used to give the probability of a person’s risk of a major fracture from osteoporosis in the next ten years. It uses information from your health history, risk factors, and bone density scans to calculate your risk. Together, you and your health care provider can use the tool to guide your treatment decisions.

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Article Sources

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