Understanding Your DEXA Results: T-Scores and Z-Scores Explained
Your DEXA report gives your bone density as a T-score, and often a Z-score as well. The T-score compares your bone density to that of a healthy young adult and is the number used to identify low bone mass and osteoporosis. The Z-score compares you to other people your own age and sex, and it helps flag bone loss that aging alone doesn’t explain.
In this post, we’ll be discussing what a DEXA scan actually measures, how to read your T-score and Z-score, why your spine and hip numbers may not agree, and what said results mean for your spine health. Read on to learn more!
What a DEXA Scan Actually Measures
A DEXA scan, short for dual-energy X-ray absorptiometry, uses a very low dose of X-ray to measure the mineral content packed into your bones. That measurement is your bone mineral density, and it’s the best available predictor of your future fracture risk.
The scan typically measures your lumbar spine and one or both hips, since those are the sites where a fracture changes a person’s life the most. Your report then converts that raw density into scores that can be compared against reference populations. If you’d like the practical details on the scan itself, our DEXA scan page answers the common questions, and our post on the benefits of DEXA scans beyond osteoporosis covers what else the test can reveal.
What Is a T-Score?
Your T-score is the difference between your bone density and the bone density of a healthy young adult at peak bone mass, measured in standard deviations. A score of 0 means your density matches that young adult reference. Each full point below 0 represents a meaningful step down in bone strength, which is why the number is reported with a decimal rather than rounded.
As the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) explains, the lower your T-score, the higher your risk of a bone fracture. T-scores are used for women who are postmenopausal and for men age 50 and older.
Explore the T-Score Ranges
Select a range below, or tap it on the scale, to see what that result generally means.
Choose a range, or tap a band on the scale, to see what it means. Your own result should always be interpreted by your provider.
Normal bone density
T-score of -1.0 or above
Your bone density is within the range expected for a healthy young adult. This is a reassuring result.
What it doesn’t mean
A normal T-score doesn’t make you fracture-proof. Bone density is one piece of the picture, alongside your age, family history, prior fractures, medications, and fall risk.
For your spine: normal density is a good sign, yet new back pain still deserves an evaluation on its own merits.
Low bone mass, also called osteopenia
T-score between -1.0 and -2.5
Your bone density is below the young adult reference, yet not low enough to be classified as osteoporosis. Many people land here, and it is best understood as a signal rather than a diagnosis.
What typically comes next
- A review of risk factors, medications, and fall history
- A fracture risk estimate, which combines your density with your other risk factors
- A conversation about activity, nutrition, and follow-up testing
For your spine: many compression fractures occur in people whose scores sit in this range, which is why risk factors matter as much as the number.
Osteoporosis range
T-score of -2.5 or lower
Bone density at this level meets the standard threshold for osteoporosis. If you have also had a fracture from a minor injury, that combination is often described as severe or established osteoporosis.
What typically comes next
- Lab work to look for treatable contributing causes
- A discussion of treatment options with your provider
- Fall prevention planning and follow-up scans over time
For your spine: this is the range where a minor fall, a hard cough, or lifting something light can cause a vertebral compression fracture.
Z-score
Compared to others your age and sex
The Z-score doesn’t appear on the T-score scale above, because it answers a different question: is your bone density what we would expect for someone your age, rather than for a young adult?
When it’s used
Z-scores are reported for premenopausal women, men under 50, and children. A Z-score of -2.0 or lower is described as below the expected range for age, and it usually prompts a search for another cause of bone loss.
For your spine: unexplained low bone density in a younger patient is worth investigating before any planned spine procedure.
These ranges are general standards, not a diagnosis. Your provider interprets your scores alongside your history, medications, and fracture risk.
What Is a Z-Score, and Who Gets One?
If the T-score asks “how does your bone density compare to a young adult?”, the Z-score asks “how does it compare to other people like you?” It measures your density against the average for your age, sex, and body size.
This distinction matters. A 75-year-old may have a T-score deep in the osteoporosis range while her Z-score sits near average, because bone loss is expected with age. A 35-year-old with the same T-score would have a strikingly low Z-score, and that’s a signal that something beyond normal aging is at work. Certain medications, hormonal conditions, and digestive disorders that limit nutrient absorption can all drive bone loss, so a low Z-score usually leads to further testing rather than straight to treatment.
Why Your Spine Number and Hip Number May Disagree
Patients are often surprised to see a spine T-score that looks better than the hip, or vice versa. Both can be accurate. Here’s what’s often behind it:
Arthritis in the Spine: Bone spurs and degenerative changes add mineral to the area being measured, which can push your spine score artificially higher and mask real bone loss.
Previous Compression Fractures: A collapsed vertebra becomes denser, which can also raise the spine reading.
Scoliosis or Hardware: Curvature and prior surgical hardware change what the scanner sees.
Aortic Calcification: Calcium in the blood vessel in front of the spine can be captured in the measurement.
For these reasons, providers often give more weight to the hip reading in older adults, and may exclude individual vertebrae from the spine calculation. If your report notes that a level was excluded, that’s a sign your results were read carefully rather than a sign of an error.
What Your Results Mean for Your Spine
Bone density is not an abstract number to a spine practice. Weakened vertebrae are the reason a minor fall or even a hard cough can lead to a vertebral compression fracture, which the Merck Manual notes most often results from slight or no force in older adults with osteoporosis.
Your bone density also shapes surgical planning. Screws and other hardware need solid bone to hold securely, so knowing your density in advance helps our surgeons choose the safest approach and may change the recommended technique. This is why we may order a DEXA scan as part of a workup even when osteoporosis screening isn’t the reason you came in.
One important exception is worth knowing: if you have already had a fracture from a minor injury, that fracture carries diagnostic weight on its own, regardless of what your T-score says. If you suspect a recent vertebral fracture, our team offers emergency compression fracture treatment.
Questions Worth Asking About Your Results
Bring your report to your appointment and use these to guide the conversation:
Which Site Is Driving My Diagnosis? Ask whether your spine or hip reading is the one being used, and why.
Was Anything Excluded? Ask whether any vertebrae were left out of the calculation and what that means for your result.
What Is My Overall Fracture Risk? Your density is one input. Ask how your age, history, and medications factor in.
Could Something Else Be Causing This? Particularly relevant if your Z-score is low for your age.
When Should I Be Rescanned? The right interval depends on your result, your risk factors, and whether you have started treatment. Ask your provider what makes sense for you and, if possible, return to the same facility and machine so the comparison is reliable.
Frequently Asked Questions
Is a T-score of -2.0 bad?
A T-score of -2.0 falls in the low bone mass range, often called osteopenia. It means your bone density is below the young adult reference but has not reached the osteoporosis threshold. It is best treated as an early warning that makes risk factors, activity, nutrition, and follow-up testing worth discussing with your provider.
What is the difference between a T-score and a Z-score?
A T-score compares your bone density to a healthy young adult at peak bone mass and is used to identify low bone mass and osteoporosis. A Z-score compares your density to the average for people of your own age and sex, which helps reveal bone loss that normal aging does not explain.
Why is my spine T-score different from my hip T-score?
Arthritis, bone spurs, previous compression fractures, scoliosis, surgical hardware, and calcium in nearby blood vessels can all add apparent density to the spine measurement. That can make a spine score look better than the hip. Providers often weigh the hip reading more heavily in older adults for this reason.
What Z-score is considered low?
A Z-score of -2.0 or lower is generally described as below the expected range for age. Rather than being a diagnosis on its own, it prompts a closer look for contributing causes such as certain medications, hormonal conditions, or digestive disorders that affect how your body absorbs nutrients.
Can my T-score improve?
Bone density changes slowly, and modest improvement or stabilization is possible depending on the cause of your bone loss and the approach you and your provider choose. Because normal scan-to-scan variation exists, repeat testing is usually spaced out and ideally performed on the same machine for a fair comparison.
Does a normal T-score mean I cannot break a bone?
No. Bone density is one part of fracture risk, alongside age, prior fractures, family history, certain medications, and your likelihood of falling. Many fractures happen in people whose scores are not in the osteoporosis range, which is why the full picture matters more than a single number.
Bring Your DEXA Results to Us
Your DEXA report is a valuable piece of information, and it’s most useful when someone reviews it alongside your history and your symptoms. If you have questions about your results, or you’d like to discuss what they mean for your spine, you’ll want to contact us using the form below or call our office at 210-255-8935. We’ll be sure to respond as soon as possible. We look forward to hearing from you soon!
DISCLAIMER: No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.