As someone living with osteoporosis, you may have had a bone density scan taken to help your doctor diagnose the condition. However, your doctor may recommend follow-up scans to test the density of your bones over time.
While the scans aren’t themselves a treatment for osteoporosis, some doctors use them to monitor how medications and other osteoporosis treatments are working.
What is a bone density scan?
A bone density scan is a painless, noninvasive test that uses X-rays to detect how dense bones are in key areas. These may include your spine, hips, wrists, fingers, kneecaps, and heels. However, sometimes doctors only scan certain areas, such as your hips.
A bone density scan may also be completed using a CT scan, which provides more detailed and three-dimensional images.
Different types of bone density scanners exist:
- Central devices can measure the density of bones in your hips, spine, and total body.
- Peripheral devices measure bone density in your fingers, wrists, kneecaps, heels, or shinbones. Sometimes pharmacies and health stores offer peripheral scanning devices.
Hospitals typically have the larger, central scanners. Bone density scans with central devices may cost more than their peripheral counterparts. Either test can take anywhere from 10 to 30 minutes.
The scan measures how many grams of calcium and other key bone minerals are in portions of your bone. Bone density scans aren’t the same thing as bone scans, which doctors use to detect bone fractures, infections, and cancers.
According to the U.S. Preventive Services Task Force, all woman older than age 65 should have a bone density test. Women younger than age 65 who have risk factors for osteoporosis (like a family history of osteoporosis) should have a bone density test.
Understanding the results of a bone density scan
A doctor will review your bone density test results with you. Usually, there are two major numbers for bone density: a T-score and a Z-score.
A T-score is a measurement of your personal bone density compared with a normal number for a healthy person that’s age 30. The T-score is a standard deviation, meaning how many units a person’s bone density is above or below average. While your T-score results may vary, the following are standard values for T-scores:
- –1 and higher: Bone density is normal for age and gender.
- Between –1 and –2.5: Bone density calculations indicate osteopenia, meaning bone density is less than normal.
- –2.5 and less: Bone density indicates osteoporosis.
A Z-score is a measurement of the number of standard deviations compared with a person of your age, sex, weight, and ethnic or racial background. Z-scores that are less than 2 can indicate a person is experiencing bone loss that isn’t expected with aging.
Risks for a bone density scan
Because bone density scans involve X-rays, you’re exposed to some degree of radiation. However, the amount of radiation is considered small. If you’ve had many X-rays or other exposures to radiation over the course of your life, you may wish to talk with your doctor about potential concerns for repeated bone density scans.
Another risk factor: Bone density scans may not correctly predict fracture risk. No test is always 100 percent accurate.
If a doctor tells you that you have a high fracture risk, you may experience stress or anxiety as a result. This is why it’s important to know what you and your doctor will do with the information a bone density scan provides.
Also, a bone density scan doesn’t necessarily determine why you have osteoporosis. Aging can be one of many causes. A doctor should work with you to determine if you have other contributing factors that you could change to improve bone density.
Benefits to getting a bone density scan
While bone density scans are used to diagnose osteoporosis and also predict a person’s risk for experiencing bone fractures, they also have value for those already diagnosed with the condition.
A doctor may recommend bone density scanning as a means to gauge if osteoporosis treatments are working. Your doctor can compare your results to any initial bone density scans to determine if your bone density is getting better or worse. According to the National Osteoporosis Foundation, healthcare providers will often recommend repeating a bone density scan one year after treatments start and every one to two years after that.
However, expert opinions are mixed as to the helpfulness of regular bone density scans after a diagnosis has been made and treatment started. One study examined almost 1,800 females being treated for low bone mineral density. The researchers’ findings uncovered that doctors rarely made changes to a bone density treatment plan, even for those whose bone density decreased after treatment.
Questions to ask your doctor about bone density scans
If you’re taking osteoporosis medications or have made lifestyle changes to strengthen your bones, your doctor may recommend repeat bone density scans. Before undergoing repeated scans, you can ask your doctor the following questions to see if repeated scans are the best choice for you:
- Does my history of radiation exposure put me at risk for further side effects?
- How do you use the information you get from the bone density scan?
- How often do you recommend follow-up scans?
- Are there other tests or measures I can take that you would recommend?
After discussing potential follow-up scans, you and your doctor can determine if further bone density scans may improve your treatment measures.