Frequently Asked Questions about Bone Density Testing
What is a bone density test?
A bone density test is called a DXA or DEXA scan. This is not the same test as a bone scan. A bone density test uses a small amount of x-ray to measure the amount of mineral in the bones of your lower back, hip or the forearm. This test helps identify those at risk of having osteoporosis.
Why is a bone density test done?
Bone density tests are used to identify persons at risk for breaking bones. The test scores can be used by your provider to help you maintain healthy bones and recommend medication when appropriate.
How is a bone density test done?
The exam is performed by a radiographer who specializes in X-ray. You will lie on your back on a padded table. You may be able to remain fully clothed or change into a patient gown. The machine will move slowly over the areas to be scanned. You will not need to go into a tunnel, the machine is very open. You will not be given any medications or injections.
How long does a bone density test take?
Usually, the test takes 15-20 minutes.
What information does a bone density test provide?
For postmenopausal women and men above age 50 a T-score is reported. A T-score is a measure of bone mineral density as compared to a young adult. Your T-score has a diagnostic range.
- T-scores of -1.0 and above are considered normal.
- T-scores of -1.1 to -2.4 are considered to be low bone mass or osteopenia.
- T-scores of -2.5 and lower are considered to be osteoporosis.
For children, premenopausal women and men below age 50, a Z-score is reported. Z-scores compare your scores with others of your gender, ethnicity and age. A Z-score of -2.0 is considered below the normal range for age group.
When should I have my first bone density test?
The timing of your first bone density test (baseline) should be determined by talking to your health care provider. Certain conditions and medications can influence when you have your first bone density test. If you are a woman age 65 or older or if you are a man age 70 or older you should have a bone density test. Testing should be considered in menopausal and postmenopausal women below age 65 with risk factors, men age 50-69 with risk factors and anyone with a fragility fracture. A fragility fracture is a low impact fracture that occurs when falling from sitting or standing height and typically involves the hip, spine or forearm.
When should I have my follow up bone density test?
A follow up bone density test is often done after 2 years. However, if you have certain medical conditions or take certain medications, your health care provider may recommend more frequent testing. The follow up test needs to be done at the same facility and on the same machine as the baseline. The follow up test will compare to the previous to see what change has occurred.
You should check with your insurance company for how often this test will be covered.
What are some risk factors for bone mineral loss (osteoporosis)?
- Being female
- Asian or Caucasian ethnicity
- Long term oral glucocorticoid medication use (prednisone)
- Menopausal or postmenopausal
- Small body build
- Alcohol use of more than 2 drinks per day
- Family history of osteoporosis
- Fragility fracture
- Excessive exercise resulting in loss of menstrual periods
- Men with low testosterone levels
- People with a diet low in calcium and vitamin D
- Bowel diseases
How much radiation exposure do I get?
The amount of x-ray exposure you get is about the same as one to two days of background radiation from normal life. This is less than the radiation you get from flying from the east coast to the west coast and about 1/10th of the exposure from a chest x-ray. This test should be avoided if you are pregnant.