Everything you need to know about a DEXA scan
A bone density test, also known as a DEXA scan or DXA, stands for Dual Energy X-Ray Absorptiometry. DEXA scans are the most widely used test to measure bone mineral density.
This measurement reflects the fact that the denser the bone, the less x-rays pass through it.
Usually, the denser your bone, the stronger it is, and the less likely it is to fracture. (Although this isn’t always the case, as we’ll cover a little further down the page!)
If you’ve ever had an x-ray, the process is very similar.
A DEXA 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 x-ray sources 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.
Then, the amount of x-rays passing through the bone is sent to a computer that calculates an average score for the density of your bone.
A DEXA scan is more accurate than a regular x-ray or CAT scan and requires less radiation exposure. More on this in a moment.
But first, let’s go over the different types of DEXA scans!
Who Should Get a DEXA Scan?
DEXA scans are the best method to diagnose and monitor osteopenia and osteoporosis. The National Osteoporosis Foundation’s guidelines state you should get a DEXA scan if:
- you are a woman age 65 or older
- you are a man age 70 or older
- you break a bone after age 50
- you are a woman of menopausal age with risk factors
- you are a postmenopausal woman under age 65 with risk factors
- you are a man age 50-69 with risk factors
There are numerous factors that can increase your risk of osteoporosis. Below are a few to watch out for. If you say, “That’s me” to two or more items on this list, it may be a good idea to ask your doctor about a DEXA scan!
- Gender: Women are at higher risk of developing osteoporosis. This is because estrogen decreases sharply during menopause which accelerates bone loss. In fact, in the five to seven years following menopause, a woman can lose up to 20% of her bone density.²
- Age: In your lifetime, you increase bone mass from childhood to about your mid-thirties, when you reach your peak bone mass. Then, after age 40, you lose about 1% bone density every year.³
- Lack of Exercise: Weight-bearing exercise is one of the best things you can do to strengthen your bones. This type of exercise places stress on your bones, which helps them become stronger. On the other hand, if you don’t exercise, your bones will become weaker over time.
- Diet: A diet lacking in essential nutrients plays a major role in the development of osteoporosis. As you’re no doubt aware, calcium is crucial for healthy bones. But you also need 12 other minerals and three vitamins to support your bone health! Learn more about diet and nutrition here.
- Family History: Having a family member with osteoporosis puts you at greater risk because osteoporosis has a strong genetic component.⁴
- Body Size: Women and men who have small body frames tend to have a higher risk for osteoporosis.⁵
How to Read Your DEXA Scan Results
Even after sitting down with your doctor, you may have follow-up questions or forgotten which numbers meant what! That’s totally normal. And that’s why we’re going to go over your T- and Z-scores (the main numbers shown after your DEXA scan), so you understand exactly what they mean.
Broadly, here’s what your T-scores mean:
- 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 a little deeper…