A bone density test, also known as a DEXA (or DXA) scan, stands for Dual Energy X-Ray Absorptiometry and is the most widely used test to measure bone mineral density. The measurement reflects the fact that the denser the bone, the less X-rays pass through. Usually the more dense your bone, the stronger it is, and the less likely it is to fracture.
If you’ve ever had an X-ray, the process is very similar.
A DXA machine uses low-energy X-rays and sends two different sources (thus the ‘D’ for “dual” in the name) through the bone in question. The two different X-ray sources are used to double the accuracy in measuring your bone density. So, your bone blocks some of the X-rays. And the more dense your bone is, the less X-rays pass through to the detector.
The amount of X-rays coming through the bone from each of the two X-rays is sent to a computer, which calculates an average score of the density of your bone.
A DXA scan is more accurate than regular x-rays or CAT scans and requires less radiation exposure. See more about radiation and DXA scans below.
Types of Bone Density Tests
There are two DEXA scan variations:
- Central DXA looks at your whole skeleton, paying special attention to your spine and hips. These machines are usually found in hospitals and medical centers, but there are some in doctors’ offices.
- Peripheral DXA are smaller, and focus on your extremities, like your fingers, ankles and wrists. You often find peripheral DEXA machines in a doctor’s office or smaller medical exam facility, though sometimes you see them at health fairs or even at bigger shopping malls!
Both the Central and the Peripheral tests are done on an “outpatient” basis – that means no long stay in the hospital.
The Central DXA takes less than 30 minutes, and the Peripheral DXA lasts about 10 minutes.
In the Central DXA, you lie comfortably on a padded table. No need to remove your clothes – just make sure there are no zippers that might block the x-rays of your hips and spine.
Below the bed is the x-ray generator, and above you is the imaging device.
The person who performs the test will usually place a small pillow to support your legs. This helps your spine lie flat on the table – the better to get a great image. Also, you may find your foot placed in a brace – this helps keep your hip nice and still during the procedure.
The technician will help you prepare, then walks behind a protective wall. (Remember, the x-ray dose is minimal, but this person takes dozens of these x-rays every day, so they need extra protection.)
The imaging detector will pass slowly over your body. During this time you need to hold your breath, but only for a few seconds. Don’t worry, your tech will guide you through it.
The peripheral bone density tests are simpler.
You place your finger, hand, forearm or foot in a small device that obtains a bone density reading within a few minutes.
There is an additional procedure called Lateral Vertebral Assessment (LVA). An LVA is done at many centers. LVA is a low-dose x-ray examination of the spine, to screen for vertebral fractures and is also performed on the DXA machine.The LVA test adds only a few minutes to the Central DXA procedure.
The DXA bone density test usually takes less than 30 minutes, depending on the equipment used and the parts of your body being examined.The technician may ask you to complete a quick questionnaire. This helps the doctor determine if you have osteopenia, osteoporosis or some other medical condition.Your DXA results will reveal your BMD (Bone Mineral Density)– simply, how healthy your bones are. The report also lists your T-score and Z-score (more on each below).
Who Should Get a DXA Scan?
DXA scans are now the best method of diagnosing and monitoring osteopenia and osteoporosis. The National Osteoporosis Foundation’s guidelines state the following people should be tested with DXA scans: women over 65; younger postmenopausal women who have any osteoporosis risk factors; and aging men with any osteoporosis risk factors.
There are numerous risk factors that can increase your risk of osteoporosis. Below are a few for you to watch out for. If you say, “That’s me” to two or more on this list, it might be a good idea to ask your doctor about a DXA scan.
- Gender: Women are 2x more likely to develop osteoporosis than men. Due to menopause, estrogen decreases sharply, which accelerates bone loss. For example, in the five to seven years following menopause, a woman can lose up to 20% of her bone density.
- Age: In our lifetime, we increase bone mass from childhood to about our mid-thirties, when we reach our peak bone mass. From then on, we lose about 1% of our bone every year.
- Lack of Exercise: “If you don’t use them, you lose them.” Weight-bearing exercise is one of the best things you can do to increase your bone strength because of the concentrated pressure it puts on your bones.
- Diet: A diet lacking in calcium plays a major role in the development of osteoporosis. Eating calcium-rich foods and supplementing with a quality calcium supplement will ensure you are getting the adequate amounts needed.
- Family History: Having a family member with osteoporosis puts you at greater risk, as osteoporosis is genetic.
- Body Size: Women and men who have small body frames tend to have a higher risk for osteoporosis.
How Does a Bone Density Scan Work?
The following video will show you what getting a DXA scan is like. It will also tell you what you should wear to your scan to make it more comfortable for you, and easier for the technician.
A DXA scan involves lying down- generally fully clothed- on a scanning table. A scanning arm painlessly and non-invasively scans over your spine, and then over your hips, to help determine the quantity of bone that you have.
The results are calculated in a computer, and you’re told your T-score; that’s the result of the bone density test.
If your score is between 0 and -1, you are considered normal. If it’s between -1 and -2.49, it’s called low bone mass, or osteopenia. If it’s below -2.5, that’s called osteoporosis.
AlgaeCal encourages all current and future customers to measure their bone density with a DXA scan, and will guarantee an increase in bone mineral density in as little as 180 days by using AlgaeCal Plus and Strontium Boost.
The AlgaeCal Bone Health Program is using DEXA scans to monitor the bone density of patients participating in a significant clinical study being conducted by an independent team of investigators.
AlgaeCal encourages all current and future customers to measure their bone density with a DEXA scan, and will guarantee an increase in bone mineral density through the use of AlgaeCal Plus and Strontium Boost in as little as 180 days.
Should I Be Concerned About Radiation Exposure?
In short, no.
Thankfully, as you can see from the chart below, there is very little exposure when compared to numerous other types of medical imaging procedures.
|Procedure||Average Effective Dose (mSv)||Range Reported in the Literature (mSv)|
|Bone density DEXA||0.001||0.00 – 0.035|
|X-ray, arm or leg||0.001||0.0002 – 0.1|
|X-ray, panoramic dental||0.01||0.007 – 0.09|
|X-ray, chest||0.1||0.05 – 0.24|
|X-ray, abdominal||0.7||0.04 – 1.1|
|Mammogram||0.4||0.10 – 0.6|
|X-ray, lumbar spine||1.5||0.5 – 1.8|
|CT, head||2||0.9 – 4|
|CT, cardiac for calcium scoring||3||1.0 – 12|
|Nuclear imaging, bone scan||6.3||?|
|CT, spine||6||1.5 – 10|
|CT, pelvis||6||3.3 – 10|
|CT, chest||7||4.0 – 18|
|CT, abdomen||8||3.5 – 25|
|CT, colonoscopy||10||4.0 – 13.2|
|CT, angiogram||16||5.0 – 32|
|CT, whole body||variable||20 or more|
If you go back a few decades, the only place to measure the health of your bones was at a hospital using a Central full body DXA machine. But to meet the demand for the ever-increasing cases of osteoporosis, more affordable, portable machines were invented to test bone density.
DXA machines allow us to safely, quickly and painlessly spot a bone density issue well in advance, so something can be done about it– before a bone fracture alerts you to the problem.
How to Read Your DXA Scan Results
Even after you’ve sat down with your Doctor, who likely explained in great detail what it all meant, you may have gone home and had a follow-up question or forgotten which numbers meant what!
That’s totally normal.
And that’s why we’re going to discuss your T- and Z-scores (the main numbers shown after your DXA scan) so they’re easily understandable.
Here’s the basic understanding:
- Above -1 = 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
- Below -2.5 = Your bone density indicates you have osteoporosis
But let’s dig in a little more…
What’s My Z-Score and Why Is It Useful?
In technical speak, the Z-score is a measure of the number of standard deviations your bone mineral density is from the average person of your age and gender.
An easy way to think about it is that your Z-score helps you see how you’re doing compared to other people in your age range.
As you may know, one in two women over age 50 will break a bone because of osteoporosis. So if you’re over 50, the Z-score is a good way to understand how your bone health measures up to people your own age.
But when it comes to your overall bone health there is a better indication of how you’re doing. Enter the T-Score.
What is a T-Score and What Does it Tell Me?
The T-score is a measure of the number of standard deviations your bone density is from a “Young Adult’s” bone density. It gives you an idea of how you compare to someone considered to be at peak bone health.
Once you reach your peak bone mass around age 40, you begin to lose 1% of your bone mineral density each year on average. That is why comparing your bone density to a young adult’s is more practical because they are at a lower risk for fractures. The pictures below will give you a visual representation of your scores.
For both rows pictured below, the number on the top of each figure is the T-score for the Bone Mineral Density (BMD) that will be reported for any bone density test you’ve taken (Left Femur, Right Femur, Spine, or Total Body).
At the bottom of each figure is a “%” score associated with the T-score value. Using a scale of 1 to 100, the “%” score is how your BMD compares to people of your gender in the standard comparison group of “Young Adults” that is used to diagnose osteopenia and osteoporosis.
For example, if your T-score was 0.6, your “%” score would be “73%” suggesting that your BMD was better than 73 out of 100 people of your gender in the comparison group and worse than only 26 out of 100.
- The green figures above indicate above average BMD; the darker the green, the better your BMD.
- The yellow figures indicate that you are in low bone density territory.
- The orange figures indicate Osteopenia (-1.0 to -2.4) , where bone density is below normal and may lead to osteoporosis.
- The red figures indicate Osteoporosis (-2.5 and below) which is severe bone loss.
What’s the Best Way to Measure my Progress?
Your doctor may have told you your BMD has increased by X percent. While this is a good indicator of how much you improved yourself, the more telling figure is the “%” associated with your T-score, which is at the bottom of each figure shown above.
For example, let’s say your T-score increased from 0.6 to 0.8. Instead of saying it improved 0.2 points, just look up the “%” score for 0.6 (“73%”) and 0.8 (“79%”).
As you can see, your BMD went from better than 73% of “Young Adults” to better than 79% of “Young Adults” – a more accurate measure of change. Ultimately, that’s what you want to pay attention to!
Care and Treatment for Osteoporosis
Understanding osteoporosis treatments is vital for you, your family and friends and your caregivers. Osteoporosis treatments include a multifaceted regimen of diet, lifestyle habits, and osteoporosis supplements to help prevent (and hopefully reverse) further bone loss and fractures.
If your DXA test reveals you have osteoporosis, the following are care and treatment options:
- Fracture Healing: Understand bone fracture healing, the process and more to prevent and treat current fractures.
- Medications: Doctors often suggest treating osteoporosis with prescription drugs. You must be careful of some of these prescription drugs, due to their serious, negative side-effects.
- Exercise: Exercise is a crucial aspect for care and treatment of osteoporosis. You should focus on two types of exercise for optimal results.
- Lifestyle Changes: Treatments can include improved diet, exercise and increased supplementation. The best dietary supplement you can feed your bones will have a combination of calcium with the 13 trace minerals your bones need to grow denser, along with vitamins D3 and K2. As of this writing, the only calcium supplement on the planet with all these ingredients is AlgaeCal Plus.
- Bone-Building Minerals: If you are concerned about the bone-thinning disease osteoporosis, one treatment you may have heard of and considered is a combination of calcium and strontium.
For the most effective treatment – actual increases in bone density – take the plant-based calcium source AlgaeCal Plus. It not only contains natural calcium – from a plant, not a rock – it also includes all the vitamins and minerals your bones need to promote healthy density.
Clinical studies prove that it stops bone loss– but even better, increases bone density!
Now, what about strontium? Strontium is one of the basic building blocks of bones. And new studies prove it helps amplify plant calcium’s work in your bones– even tripling the amount of new bone density in far less time than taking a natural calcium supplement alone. (In fact, AlgaeCal funded a study to prove this surprising truth and had the results published in the Nutrition Journal. )
So be sure to get Strontium Boost to ensure you get the optimal levels of this vital element every day. (You can click here to discover a unique combination of these two supplements – AlgaeCal Plus and Strontium Boost – at great savings. Do your bones some good and take a look…)
Hopefully, you now have a clearer understanding of DXA scans and why they’re so important. It’s a good idea to ask your doctor about getting a DXA scan if you fall into any of the categories listed in the “Who Should Get a DXA Scan?” section above.
If you find you do have low bone density (any T-score -0.1 and below) or have been diagnosed osteopenic or osteoporotic, you should take the appropriate steps to combat that.
That includes a healthy diet, consistent exercise, and proper vitamin and mineral supplementation. Your bones require 13 trace minerals to stay strong and healthy, along with vitamins C, D, and K2. You can get all these- and an organic, plant-based calcium- inside the only bone health supplement guaranteed to increase bone density. (Even if you’re 80 or older!)
Plus, when you take AlgaeCal Plus and Strontium Boost together, you’ll consistently see increasing T-scores on your DXA scans, year after year.
Here’s to healthier bones!
Bone Density Testing FAQs
How do you check bone density?
The only truly accurate way to check your bone density is with a DXA scan. Regular x-rays will not give you the details (T-score and Z-score) your doctor needs to make an accurate diagnosis.
What is the actual name of the bone density test?
DXA stands for Dual Energy X-Ray Absorptiometry. There are two types: Central and Peripheral. The first covers your entire skeleton; the second focuses on your extremities, such as your hands or feet.
How much does it cost for a bone density test?
In the US, Medicare covers the cost of your DXA scan every two years. If you need more scans, please check with your insurance provider for complete coverage details.
In Canada, the Federal Government says that if you’re 65 and never had a DXA, Canadian Medicare will cover it. They’ll also let you do follow-up DXAs if you need them, every 2 years and cover them. Sometimes, if your treatments are annual, Medicare will cover the cost.
What if you’re under 65? Most commercial providers will cover your initial DXA if you’re post-menopausal and you have risk factors (such as smoking, genetics, or being under- or overweight.)
If your health insurance does not cover the cost of your DXA scan, you will have to pay out of pocket.
Where can I get a Bone Density Test?
Below is a directory of clinics that offer DXA scans in some of the major cities in Canada:
|Bodycomp Imaging||Vancouver||British Columbia|
|Body Composition Clinic Inc.||Edmonton||Alberta|
|The Bone Wellness Center||Toronto||Ontario|
|Medisys Montreal + (Medisys has other locations in Canada)
Below is a directory of clinics that offer DXA scans in the United States:
|Park Avenue Radiologists, P.C.
|New York||New York|
If you would like to see your DXA scan clinic listed here please contact us.
How often should I have a bone density test?
Once you reach one of the milestones listed below, you should have a DXA scan every 2 years:
- You are a woman 65 or older
- You are a postmenopausal woman under 65
- You are a man 70 or older
- You are 50 or older and recently suffered a bone fracture, especially from a minor fall
I have a metal plate/object in my body (head, arm, leg etc.), is it still safe/effective to have a body composition scan?
Yes. Since the metal object will be present in both initial and future scans, the readings will still be helpful since there is no change in the object. The metal will not greatly affect readings. A DXA scan’s beams can’t interact with the metal object like an MRI machine’s will, so while the surrounding tissue will be classified incorrectly as bone, readings will still be consistent from scan to scan.