Bone density scan results explain the strength of your bones and assess your risk of breaking a bone. Z-scores are used as the measure for adults under 50 and children.

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A bone density scan can give you information about the health and strength of your bones. It’s one noninvasive way to check your levels of calcium and other important minerals.

The most common bone density scan is the dual-energy X-ray absorptiometry (DEXA). This test only takes about 5 minutes, but it can take a few days for a radiologist to interpret the results and report them back to you.

If you’re premenopausal or younger than 50 years, it’s unlikely that you’ll need a bone density scan. But if you do have one, the most meaningful score will be the Z-score.

Read on to understand what a bone density scan is and what a Z-score means.

A bone density scan can give your healthcare professional valuable information about the composition of your bones, such as how much calcium and other minerals are present in your bones.

This information helps them know your bone strength, shows early signs of osteoporosis and is used, along with other tools like your FRAX score, to help develop a treatment plan.

A bone mineral density scan is another name for the DEXA or DXA scan. It tests the amounts of minerals in your bones, particularly calcium. DEXA scan results are reported in T-scores and Z-scores.

If you’re premenopausal or younger, the more reliable score for you will be the Z-score.

The measurements used to assign you a Z-score for a DEXA scan are usually taken from scans of your lumbar or lower spine and the neck of your femur (the area just below your hip joint). These are considered vulnerable areas, and they’re more likely to indicate whether you’re losing bone density.

In children, a DEXA scan will almost always be performed on the spine. However, DEXA scans may not be reliable in young children and may underestimate their bone mass density. Also, to be more accurate, the Z-score would need to take into account other children of similar skeletal maturity as well as age, sex, and size.

A Z-score is a mathematical term representing how much your bone density measurement compares to peopleof your same age, sex, and body size. Z-scores range from +2 to -2, with 0 being the score that is average for people of your age, sex, and body size.

If your Z-score is low (below -2.0), it may mean that you have lower bone density than other people of your age, sex, and body size. It may also mean that you’re losing bone density. Your healthcare professional may order additional tests, and you may be referred to an orthopedic specialist.

For people who are postmenopausal or over the age of 50, the results will be reported in T-scores.

Interpreting the significance of the DEXA scan Z-score in children may be difficult. Other measures such as height, weight, and body mass index (BMI) are often used to help establish an accurate assessment of a child’s bone mineral density. Scores from these assessments may be compared to the Z-score to help determine its accuracy.

This table shows the meanings of different Z-scores:

Z-scoreWhat your score means
+1–2Your bone density is higher than in others of your age, sex, and body size.
0Your bone density average for your age, sex, and body size.
-1Your bone density is lower than in others of your age, sex, and body size.
-2This score is the cut-off between possible low bone density and the range of typical bone density.
-2.5If your score is this or lower, it likely means that you have secondary osteoporosis (or if the score is for a child, they likely have low bone mineral density for their age).

Your doctor or healthcare professional will use your Z-score — along with other data — to make a diagnosis and to create a treatment plan for you.

If your Z-score is in the range that suggests you’re at a higher risk for fractures, your treatment plan might include recommendations to protect or improve your bone health.

Here’s more information about treatment for osteoporosis.

If secondary osteoporosis is suspected or diagnosed, you may need additional DEXA scans to monitor your bone density and help track the effectiveness of your treatment plan.

The following guidelines can help you manage and strengthen your bone density:

What is the FRAX?

The Fracture Risk Assessment Tool (FRAX) is a brief questionnaire that calculates your individual risk of breaking a bone in a percentage.

Questions include:

  • age
  • date of birth
  • sex (assigned at birth)
  • weight
  • height
  • previous fracture history
  • if either parent fractured a hip
  • if you currently smoke
  • glucocorticoid use
  • if you have rheumatoid arthritis
  • if you have secondary osteoporosis
  • if you consume three or more units of alcohol per day
  • results of the measurements of a DEXA scan for your femoral neck BMD (g/cm2), if you’ve had one
Was this helpful?

A bone density scan can give you valuable information about the quality and strength of your bones. It can take measurements of minerals that contribute to your bone health and help your doctor or other healthcare professional guide you on possible lifestyle changes or treatments that can help.

Your doctor may recommend you have a bone density scan if they suspect you have secondary osteoporosis or if you have one of the following risk factors for developing it:

  • take medications, including:
    • seizure medications
    • corticosteroids
    • chemotherapy
  • have gastrointestinal (GI) conditions, such as:
    • irritable bowel syndrome (IBS)
    • lupus
    • celiac disease
    • rheumatoid arthritis
  • have a metabolic condition, like:
    • diabetes
    • hyperthyroidism adrenal insufficiency
    • cystic fibrosis
  • have another health condition, such as:
    • HIV or AIDS
    • anorexia
    • a health condition that limits your mobility

Is a bone density scan painful?

A bone density scan should not be painful. It’s a noninvasive test that uses a scanner like an X-ray to take measurements that help your doctor evaluate the overall health of your bones.

How long does it take to get bone density scan results?

Although the test itself only takes about 5 minutes to complete, interpreting the results of the test takes specialized training. A radiologist skilled in reading DEXA scans will interpret your results and should present your doctor with a report.

Does everyone need a bone density test?

It’s generally recommended that all women ages 65 and older have a bone density test, but it may be recommended at a younger age if you were assigned male at birth or if you were assigned female and have certain risk factors.

Your doctor or healthcare professional may also order a bone scan even if you have no known risk factors but do have symptoms related to bone loss, such as frequent fractures or breaks.

Are a DEXA scan and a bone density scan different?

A DEXA scan is the name of the test used to perform your bone mineral density scan. These names may be used interchangeably.

A bone density scan, also known as a DEXA scan, is a test that can help your doctor or healthcare professional detect bone loss before you have severe symptoms like frequent fractures or broken bones.

Lifestyle changes and medications may be suggested to you based on your bone scan results. Talk with your doctor or healthcare professional if you think you or your child may need a bone density scan.