What a DEXA Scan Measures and Why Your Doctor Might Order One

A DEXA scan stands for "dual-energy X-ray absorptiometry," but you don't need to remember that name. What matters is understanding what the test actually does: it measures how dense your bones are by using two different types of X-rays at low doses. Think of bone density like the tightness of a sponge—dense bones have material packed closely together, while less dense bones are more porous and fragile.

Free Guide to Scheduling Your Ochsner Health Appointment →

Your doctor might order a DEXA scan for several reasons. If you're a woman over 65 or a man over 70, screening is often recommended even without symptoms. The scan catches bone loss before a fracture happens. People taking certain medications—particularly steroids like prednisone—often get scans because these drugs can weaken bones over time. If you've had a fracture from a minor fall, or if you have risk factors like rheumatoid arthritis, early menopause, or a family history of osteoporosis, your doctor may want to see how your bones are holding up.

The scan itself is quick and painless. You lie on a table fully clothed while a scanner moves over your body. There's no needle, no injection, and no enclosed space. The radiation dose is lower than a regular chest X-ray. Most scans focus on two areas: your hip and your lower spine. Some people also get a scan of the forearm.

Practical takeaway: A DEXA scan is a snapshot of your bone density at one moment in time. It's not painful or invasive, and it gives your doctor real information to work with when thinking about your bone health.

Reading Your T-Score: What the Numbers Actually Mean

Your DEXA results will include something called a "T-score." This is the main number your doctor will focus on, and it can seem confusing at first. The T-score compares your bone density to that of a healthy 30-year-old adult of your same sex. This comparison uses something called a "standard deviation"—essentially a statistical measure of how different you are from that healthy reference point.

Free Guide to Contacting Healthfirst Customer Service →

Here's how the T-score categories break down: A T-score of -1.0 or higher is considered normal bone density. A score between -1.0 and -2.5 falls into a category called "osteopenia," which means your bones are somewhat less dense than they should be, but you don't yet have osteoporosis. A T-score of -2.5 or lower indicates osteoporosis, meaning your bones have lost significant density and fracture risk is higher.

Let's use a real example. Sarah, age 68, gets her DEXA results and sees a T-score of -1.8 at her hip. This osteopenia result tells her that her bones are weaker than ideal, but she hasn't crossed into osteoporosis territory yet. This information helps her doctor decide whether medication is needed or whether lifestyle changes might be enough. Meanwhile, her neighbor Tom, also 68, has a T-score of -3.1 at his spine—clearly osteoporosis. Tom and his doctor would likely discuss medication options more urgently.

One important note: your T-score can vary between different bones. You might have normal density in your hip but osteopenia in your spine. Doctors consider all of these measurements together, not just one number. They also think about your individual risk factors. A woman who hasn't broken a bone and has no family history of fractures might approach a -2.3 score differently than a woman who fell last year.

Practical takeaway: Your T-score is a comparison to a healthy young adult. Negative numbers don't mean something is wrong with you—they're just the measurement system. The closer to zero (or above), the denser your bones.

Understanding Your Z-Score and Why It Matters Differently Than T-Score

While the T-score compares you to a healthy young adult, the Z-score compares you to people your own age and sex. This matters more than many people realize, because bone density naturally decreases as we age. A Z-score tells a different story than a T-score.

Free Guide to CareFirst Health Insurance Premium Payment →

A Z-score of around -1.0 or higher is considered normal for your age group. If your Z-score is lower than -2.0, it means your bones are considerably weaker than expected for someone your age and sex—and this might suggest something specific is causing bone loss, rather than just normal aging. This distinction can be medically important.

Here's why this matters in practice: Imagine Marcus is 45 years old and gets a DEXA scan because he's been taking prednisone for his autoimmune condition. His T-score is -2.3, which would normally indicate osteoporosis in an older person. But his Z-score is -1.5, which is closer to normal for his age. His doctor learns something valuable: Marcus hasn't lost bone density in a way that's unusual for his age, but the prednisone might still be affecting him more than someone not on the medication. The doctor would watch Marcus carefully and might adjust his treatment.

Younger people getting DEXA scans should pay attention to their Z-score more than their T-score. If you're 50 or younger and your Z-score is notably low, that's worth investigating with your doctor. It might point to conditions like celiac disease, inflammatory bowel disease, or hormonal problems that are affecting bone formation.

Practical takeaway: The Z-score is your comparison to people your age. If it's significantly lower than normal, it may signal that something specific is affecting your bones, not just typical aging.

Your 10-Year Fracture Risk and What It Predicts

Many DEXA reports now include something called your FRAX score, which stands for "fracture risk assessment tool." This number tells you the probability that you'll experience a major bone fracture—specifically at your hip, spine, forearm, or shoulder—in the next 10 years. It's not a prediction about what will happen to you specifically, but rather a statistical estimate based on population research.

Understanding CareCredit Pre-Approval and Medical Costs →

FRAX scores are expressed as percentages. Your report might say something like "10-year probability of hip fracture: 5%" or "major osteoporotic fracture: 12%." These percentages sound small, but they carry weight when a doctor is deciding about treatment. Generally, doctors consider a 10-year major fracture probability of 20% or higher (or 3% or higher for hip fracture alone) as worth treating with medication.

The FRAX tool considers not just your bone density but also your age, sex, weight, height, and personal or family history of fractures. A 72-year-old woman who weighs 110 pounds with a history of a wrist fracture and a T-score of -2.2 might have a projected 10-year hip fracture risk of 18%. That same T-score in a 65-year-old woman who weighs 160 pounds with no fracture history might show only 8% risk. The numbers look similar, but the overall picture is different.

It's worth asking your doctor specifically about your FRAX score if it's not in your report or if you don't understand it. Some practices calculate it automatically; others do it only on request. Knowing this number helps you have a concrete conversation about whether bone-protective medications make sense for your situation. If your risk is low, lifestyle changes might be all you need. If your risk is higher, medication becomes a more reasonable consideration.

Practical takeaway: Your 10-year fracture risk is a number that helps guide treatment decisions—it's not a certainty, but a statistical tool based on research about people similar to you.

How to Interpret Results Across Different Bones and Time

Your DEXA scan may measure bone density at multiple locations: the lumbar spine (lower back), the femoral neck (upper thighbone), the total hip, and sometimes the forearm. You might see different T-scores at each location. This is normal. Bone loss doesn't happen uniformly throughout your skeleton.

Free Guide to Reaching Ochsner Health for Appointments →

For example, Elena receives her DEXA report showing: lumbar spine T-score of -1.2, femoral neck T-score of -2.1,