Testing your bone density – how strong your bones are – is the only way to know for sure if you have osteoporosis. This condition causes your bone tissue to break down faster than new tissue can be made. As a result, your bones become weak and prone to breaks, especially in your hips, spine, and wrists.
The most widely used type of bone density scan is called dual energy X-ray absorptiometry (DEXA or DXA). This painless test measures the mineral content of your bones. That allows your doctor to assess your bone health and your risk of bone fractures.
DEXA scanning focuses on two main areas – your hip and your spine. If you can’t test those, you can get a DEXA scan on your forearm. These areas can give your doctor a good idea of whether you’re likely to get fractures in other bones in your body.
DEXA scan vs. bone scan
A DEXA scan and a bone scan are different tests.
A bone scan, or scintigraphy, is often used to look for an infection or abnormal cells, like cancer cells, inside your bone tissue. But it can also be used to check your bone density.
First, a safe, very small amount of radioactive material is put into your vein. A special camera traces it through your body, then images of your bones are created on a computer. Any abnormal cells in your bones will appear brighter or darker than normal cells.
A DEXA scan procedure is a more common, faster way to check for osteoporosis. It's more like an X-ray. A special machine sends two invisible X-ray beams into your body. One type is absorbed by your tissue, the other is absorbed by your bones. When these numbers are subtracted from each other, the number left is your bone mineral density.
DEXA Scan Cost
How much you'll pay for a DEXA scan depends on if you have insurance, what kind of insurance you have, the reasons that your doctor wants you to have it, and where you get it done. In other words, there's no easy answer.
For instance:
Under the Affordable Care Act, if you get your test done within your health plan's network, there should be no cost to you if you're assigned female at birth (AFAB) and over the age of 65.
Medicare may cover a DEXA scan if one or more of the following is true:
- You're AFAB, low on estrogen, and at risk for osteoporosis, based on your health history.
- X-rays show possible osteoporosis or other bone issues.
- You're on long-term steroids or steroid-type drugs.
- You have a thyroid condition.
- You've started medication for osteoporosis and your doctor wants to check your progress.
Many other health plans also cover some of the cost of a DEXA scan if your doctor orders the test and shows that it's medically needed.
If you don't have health insurance or your plan won't cover a DEXA scan, you may pay $160-$175 out of your own pocket.
DEXA Scan Preparation
To get ready for your scan:
Stop taking calcium supplements at least 24 hours before your appointment. This includes multivitamins and over-the-counter antacids. If you have questions about whether to stop taking a specific supplement or medication, call your doctor's office.
Dress comfortably. Wear loose clothes without a metal zipper, snaps, or belt.
Leave your jewelry at home. Or be prepared to remove it and put it somewhere safe before the procedure. You'll also be asked to remove any dental appliances.
Let your doctor know ahead of time if you've recently had a:
- Barium exam
- CT scan
- Radioisotope scan
If so, you may need to wait 10 days to 2 weeks before you can safely have a DEXA scan.
It's important to let your doctor and the tech know before you have a DEXA scan if you're pregnant, or think you might be. Although the radiation you're exposed to during this test is low, it could still harm your baby. If your doctor feels you must have this scan, then the tech can take extra steps to keep you safe.
DEXA Scan Procedure
Once you arrive for your appointment, you'll fill out a questionnaire that asks about your family history, daily habits, and any bones you've broken. Then, you'll be asked to take off any eyeglasses, jewelry, and anything metal. You may also need to change into a hospital gown.
Unlike some other tests, like MRIs or CT scans, you won’t have to lie inside a closed tunnel or ring for a DEXA scan. Instead, you’ll lie on an open X-ray table. A tech may use foam blocks to keep your body in a certain position. Then, you'll try to stay still as the DEXA scanner passes over you. You could also be asked to hold your breath for a few seconds.
Images of your bones will show up on the tech's computer screen. Bones will show up as white, while tissue and fat will look like shadows.
When the test is over, you’ll be able to go home. A radiologist will read your results and send your doctor a written report of their findings. They'll then talk to you about any treatment or other tests you might need.
This test is quick and painless, and the amount of radiation you get from the X-rays is low.
How often should you get a DEXA scan?
Once you have this test, current guidelines suggest that you have it again every 2 years. That way, doctors can check to see if your bones are getting stronger or weaker. But many factors can change that time frame, such as your age, other health conditions you have, medications that you take, and how concerned your doctor is that you'll break a bone.
How long does the scan take?
Generally, a DEXA scan takes about 15 minutes.
How accurate is a DEXA scan?
It's considered the "gold standard" for checking bone density. But it does have some limits. For instance:
- It can't say for sure if you'll break a bone, only how at risk you are.
- If you have arthritis, a spinal fracture, or another condition that affects the bones in your back, a CT scan may be more accurate than a DEXA scan.
- Some older types of DEXA machines may be less sensitive than newer ones. So it may be hard to compare results that you received from two different testing centers.
- Sometimes, a DEXA scan measures only your heel or wrist to figure out how likely you are to fracture your spine or hip. This measurement isn't the best way to choose a treatment plan.
Who Should Get a DEXA Scan?
If you're AFAB, you're more likely to get osteoporosis than someone who's assigned male at birth (AMAB.) The U.S. Preventive Services Task Force advises getting a DEXA scan for bone density if you're:
- AFAB and age 65 or older
- AFAB and age 60 or older and have a higher chance of getting a fracture
Talk to your doctor about whether the test is a good idea for you.
Anyone can get osteoporosis, and as you get older, your risk naturally rises. You're also more likely to have issues with your bones if you're Asian American or White. Other things that raise your risk include:
- Hormone changes (like going through menopause)
- Not getting enough calcium and vitamin D
- Tobacco use
- Heavy alcohol use
- Not getting enough exercise
- A low body weight
- Having a parent with osteoporosis or a broken bone
Certain health conditions, like rheumatoid arthritis, celiac disease, and cancer, can increase your chances of having osteoporosis. Some medicines, including steroids and gastric reflux drugs, can also raise your risk.
DEXA Scan Results
For the results of your scan, you’ll get two numbers.
T-score: This number shows how dense your bones are, compared to an adult of the same gender. The lower your score, the weaker your bones are:
- T-score of -1.0 or above = normal bone density
- T-score between -1.0 and -2.5 = low bone density, or osteopenia
- T-score of -2.5 or lower = osteoporosis
Z-score: This number compares your bone density to a normal score for a person of your same gender, age, and body size. If it's very high or low, your doctor may suggest other tests to get more information.
Your test results can vary slightly, based on the position you're in during the DEXA scan.
Does a DEXA scan show cancer?
A DEXA scan only measures how much bone you have. The other type of bone scan called a scintigraphy can show your bones in more detail. The tiny amount of radioactive substance that 's put into your body for that test can reveal "hot spots" that could be cancer that's started in your bones or has spread to your bones from somewhere else in your body. If so, your doctor will order different types of tests to get more information and make a diagnosis.
Takeaways
A DEXA scan measures the density of your bones. It's a good test to have as you get older, especially if you have a family history of osteoporosis or broken bones. If your DEXA results show that your bones are weak, your doctor can suggest lifestyle changes, medication, and ways to lower your risk of falls.
DEXA Scan FAQs
What is the difference between a DXA and DEXA scan?
There's no difference. They're the same imaging test. DEXA stands for "dual-energy X-ray absorptiometry." Doctors tend to use DXA as shorthand for "bone densitometry test."
Is a DEXA scan an MRI scan?
No. While both are imaging tests, they're very different. An MRI uses magnetic fields to make 3D images of your entire body. A DEXA scan uses low-level X-rays to measure how dense your bones are.
