A DXA scan (bone density test) is a quick, painless way to check your
bone health. It’s similar to a regular X-ray, but measures the strength
and mineral content of your bones instead of just taking pictures of
them. Providers use DXA scans to screen you for osteoporosis, osteopenia
and other conditions that can silently weaken your bones.
Key Takeaways
A bone density test measures how much calcium and
minerals are in your bones to see if you are at risk for
fractures.
The test is quick and painless, taking 10 to 30 minutes,
and results are ready in a few days.
The results include a T-score that helps doctors see if
you have normal bone density, low bone density (osteopenia),
or osteoporosis.
Overview
What is a DXA scan?
A DXA scan is an imaging test that measures the strength of your bones.
It uses X-rays to measure your bone density. DXA is an abbreviation for
dual-energy X-ray absorptiometry.
Healthcare providers sometimes refer to DXA scans as bone density scans,
DXA scans or bone density tests. All of these are different names that
refer to the same test. They used to be known as DEXA scans or DEXA
tests, but healthcare providers don’t use that term anymore.
What is a DXA scan used to diagnose?
A healthcare provider might use a DXA scan to check your bones in a few
situations, including to:
Diagnose osteoporosis.
Diagnose osteopenia.
Check your bone
fracture risk.
Your provider might use a bone density test to see how your bones have
changed over time, including:
Measuring the natural amount of bone loss that happens as you age
and tracking your bone loss over time.
Evaluating your bone density before you start a treatment or
medication that can weaken your bones as a side effect.
Checking if your bones are responding to treatment
for osteoporosis or osteopenia.
When will I need a DXA scan?
Anyone might need their bone density checked with a DXA scan. Your
healthcare provider will suggest one if they want to check your bone
density and fracture risk.
Some people have a naturally higher risk of developing osteoporosis and
other conditions that affect their bone density. Groups who need regular
DXA scans include:
Females older than 65.
Males older than 70.
People older than 50 who’ve broken a bone in the past.
People whose biological parents or grandparents have osteoporosis.
People who’ve lost an inch and a half or more of height from their
tallest height (usually when you’re in your 20s).
Lack of physical activity
Early menopause
People younger than the ages above who have an increased risk of bone
loss may need regular DXA scans, too. Your provider will tell you when
(and how often) you should get your bone density checked.
Some health conditions or certain medications can increase your risk for
bone density issues, including:
Proton pump inhibitors (PPIs) that treat acid
reflux and GERD.
Heparin (a blood thinner).
Benefits
Detects weak or brittle bones to help predict the odds of a future
fracture.
Determines if bone density is improving, worsening, or staying the
same.
Can help you and your healthcare provider come up with plans to
improve your bone strength and prevent worsening conditions.
Risks
Limitations of bone density testing include:
Differences in testing methods. Devices that measure
density of the bones in the spine and hip are more accurate but cost
more than do devices that measure density of the peripheral bones of
the forearm, finger or heel.
Previous spinal problems. Test results may not be accurate
in people who have structural abnormalities in their spines, such as
severe arthritis, previous spinal surgeries or scoliosis.
Radiation exposure. Bone density testing uses X-rays, but
the amount of radiation exposure is usually very small. Even so,
pregnant women should avoid these tests.
Lack of information about the cause. A bone density test
can confirm that you have low bone density, but it can't tell you
why. To answer that question, you need a more complete medical
evaluation.
Limited insurance coverage. Not all health insurance plans
pay for bone density tests, so ask your insurance provider
beforehand if this test is covered.
Test Details
How is a bone density test done?
A bone density scan uses low levels of X-rays to measure the density and
mineral content of your bones. It’s similar to a typical X-ray.
That’s what the X in DXA stands for.
DXA scans are outpatient procedures, which means you won’t have to stay
in the hospital. There are no needles or injections in this test, and
you won’t feel any pain.
You might be able to wear your regular clothes during the test, or you
may have to change into a hospital gown.
Here’s how a bone density scan works:
You’ll lie on a special X-ray table.
A technician (a radiologic
technologist) will help you position your body. They might put
foam blocks under or around you to hold your legs in the proper
position.
The technician will pass a scanning arm over your body that takes
pictures of your bones. Technicians usually scan your hips and
spine, but they may take scans of other bones throughout your body,
too, like your forearms.
A bone density scanner uses two types of low-level radiation to
translate your bone density into pictures and graphs on a computer. Your
bones will show up as white. Fat, muscles and
other soft tissue will look like dark shadows in the background of the
test images.
What should you not do before a DXA scan?
You probably won’t have to change your usual routine before having a
bone density test. In general, you can:
Eat and drink before your test.
Take all your usual medications, unless your provider asks you not
to.
Wear comfortable, loose-fitting clothing to your test. Try to wear
items that don’t have metal (zippers, buttons or buckles). You’ll
have to remove clothing and jewelry that contains metal before the
test.
If you take a calcium supplement or other over-the-counter (OTC)
vitamins, don’t take them 24 hours before your test. Tell your provider
which vitamins and supplements you take. They’ll let you know which ones
you can or can’t take before a DXA scan.
You won’t be able to have a DXA scan within 24 hours of certain other
kinds of imaging tests. Tell your scheduler when you’re having other
tests before you make your DXA scan appointment.
How long does a bone density test take?
A bone density test usually lasts around 30 minutes. Your test might be
slightly shorter or longer depending on how many of your bones need
scanning.
What are the disadvantages of a DXA scan?
There are very few risks to having a bone density test. You won’t feel
any pain or have any side effects after the scan.
You shouldn’t have a bone density test if you're pregnant. Tell your
provider if you’re pregnant or think you might be pregnant. DXA scans
use such a low level of radiation that they’re harmless for almost
everyone, but if you're pregnant you should avoid all forms of radiation
if possible.
Some studies have found that results and readings from DXA scans can
vary between manufacturers of the scanning machines, but that’s not
usually something you need to worry about. Your provider will monitor
changes in your bone density over time and will suggest repeated or
different tests if needed.
Results and Follow-Up
What type of results do you get from a DXA scan and what do they mean?
The results of a DXA scan will show how dense your bones are.
The results of your bone density test will have two scores: a
T-score and a Z-score.
T-score
Your T-score is your bone density compared with what is normally
expected in a healthy young adult of your sex. Your T-score is
the number of units — called standard deviations — that your
bone density is above or below the average.
T-score
What your score means
-1 and above
Your bone density is considered normal.
Between -1 and -2.5
Your score is a sign of osteopenia, a condition in which
bone density is below normal and may lead to osteoporosis.
-2.5 and below
Your bone density indicates you likely have osteoporosis.
Z-score
Your Z-score is the number of standard deviations above or below
what's normally expected for someone of your age, sex, weight,
and ethnic or racial origin. If your Z-score is significantly
higher or lower than the average, you may need additional tests
to determine the cause of the problem.
Your provider will discuss the results with you and explain what they
mean. If you have a lower-than-usual bone density, your provider will
suggest treatments to help keep your bones strong, including:
Exercising more often: Regular physical activity
strengthens your bones. Walking, yoga and strength training are
great ways to stay active and prevent bone loss.
Supplements or eating specific foods: Your provider might
suggest that you take a vitamin D or calcium supplement to support
your bone health. You might need to eat more foods high in certain
vitamins and minerals.
Medication: Your provider might prescribe medications that
help slow down bone loss and prevent fractures. Some medications for
osteoporosis may help build your bone density.
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.
Additional Common Questions
What is the difference between a DXA scan and a whole-body bone scan?
DXA scans and whole-body bone scans are similar tests. Both tests
involve scanning your bones, but providers use them to check different
aspects of your bone health.
DXA scans are special X-rays that measure your bone density to screen
you for osteoporosis and other conditions that weaken your bones.
A whole-body bone scan lets providers check to see if
a cancer you might have has spread (metastasized) to your bones.
You might also need a whole-body bone scan to see which cancer
stage you have. They can also detect infections, lesions and
other issues.
One Final Note..
A DXA, DEXA or bone density scan. No matter what your provider calls it,
this is a quick, easy (and painless) test. It’ll help your provider
catch conditions that affect your bone density as soon as possible. You
may need regular bone density screenings based on your age, family
history or other risk factors you might have.
Everyone should have their bone density checked as they age. Ask your
provider how often you need a DXA scan. Anyone with a family history of
osteoporosis will need bone density screenings more often. Your provider
will help you maintain your bone health to make sure your bones are
strong enough to support you throughout your life.
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