Bone Density T-Score and Z-Score: Charts by Age and What Your Numbers Mean
Medically reviewed by Medical Advisory Board Last reviewed 2026-07-29
How to read your DEXA scan results — reference ranges, clinical thresholds, and when to worry
Your DEXA T-score classifies bone as normal, osteopenia, or osteoporosis. See reference ranges, female age norms, when Z-score matters, and what to do next.
When you receive DEXA scan results, the most important numbers are your T-scores at the lumbar spine and hip. The T-score compares your bone mineral density to the average peak bone mass of a healthy 30-year-old of the same sex. The World Health Organization uses the T-score to classify bone health into three categories: normal (above -1.0), osteopenia (-1.0 to -2.5), and osteoporosis (below -2.5).
The Z-score provides a different comparison — your bone density relative to people of the same age and sex. While the T-score drives diagnosis and treatment decisions, a low Z-score (below -2.0) is a red flag that your bone loss is worse than expected for your age, prompting investigation for secondary causes.
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| T-Score | WHO Classification | What It Means | Approximate Fracture Risk Increase |
|---|---|---|---|
| +1.0 to -1.0 | Normal | Bone density within 1 SD of young adult average | Baseline |
| -1.0 to -1.5 | Mild osteopenia | Modestly reduced bone mass | 1.5-2x |
| -1.5 to -2.0 | Moderate osteopenia | Moderately reduced bone mass | 2-3x |
| -2.0 to -2.5 | Severe osteopenia | Approaching osteoporosis threshold | 3-4x |
| Below -2.5 | Osteoporosis | Significantly reduced bone mass | 4-8x |
| Below -2.5 + fracture | Severe osteoporosis | Osteoporosis with fragility fracture | 8-12x |
Key principle: Each 1-SD decrease in T-score approximately doubles the age-adjusted fracture risk. A T-score of -2.0 carries roughly 4x the fracture risk of a T-score of 0.
Average Bone Density by Age (Women)
| Age | Avg Lumbar Spine T-Score | Avg Femoral Neck T-Score | Notes |
|---|---|---|---|
| 30 (peak) | 0.0 | 0.0 | Reference standard (peak bone mass) |
| 40 | -0.2 to -0.5 | -0.1 to -0.3 | Minimal age-related decline |
| 50 | -0.5 to -1.0 | -0.5 to -0.8 | Perimenopause begins; decline accelerates |
| 55 | -1.0 to -1.5 | -0.8 to -1.2 | Early postmenopause; rapid loss phase |
| 60 | -1.2 to -1.8 | -1.0 to -1.5 | Many women cross into osteopenia |
| 65 | -1.5 to -2.2 | -1.2 to -1.8 | Screening recommended for all women |
| 70 | -1.8 to -2.5 | -1.5 to -2.2 | Osteoporosis prevalence ~25% |
| 80 | -2.0 to -3.0 | -2.0 to -2.8 | Osteoporosis prevalence ~40% |
Values are population averages. Individual variation is significant — genetics, exercise history, hormone status, and nutrition create wide ranges at every age.
T-Score vs. Z-Score: When Each Matters
T-score (used for diagnosis in postmenopausal women and men over 50):
- Compares to young adult peak bone mass (age 30 reference)
- Used to diagnose osteopenia and osteoporosis per WHO criteria
- Drives treatment decisions and FRAX risk calculation
Z-score (preferred for premenopausal women, men under 50, and children):
- Compares to age- and sex-matched reference population
- A Z-score below -2.0 is classified as 'below the expected range for age'
- Triggers investigation for secondary causes: vitamin D deficiency, hyperparathyroidism, celiac disease, medications, eating disorders, chronic inflammatory conditions
The Z-score answers: 'Is this bone loss worse than expected for my age?' A 65-year-old woman with a T-score of -2.0 but a Z-score of 0 has age-appropriate bone density. The same T-score with a Z-score of -2.5 suggests an additional pathological process beyond normal aging.
How Often Should Menopausal Women Get a DEXA Scan?
Screening frequency around menopause depends more on age and individual risk factors than on menopausal status by itself. As a general pattern drawn from Bone Health & Osteoporosis Foundation and USPSTF-aligned guidance: routine screening for average-risk women generally starts at age 65, women with risk factors (early or surgical menopause, family history of hip fracture, low body weight, long-term corticosteroid use, prior fragility fracture) are often screened earlier, and a normal baseline is typically rechecked roughly every 2 years — sooner and more consistently if the baseline already shows osteopenia. For the full breakdown by age and risk factor, see our DEXA scan guide.
T-Score & Z-Score Interpreter
Enter the T-score from your DEXA report (and the Z-score, if you have it) to see what it means using the WHO classification above. Use the "T-score" line specifically — not the BMD value in g/cm². This tool is educational only and does not replace a review with your doctor.
What Makes a Good Bone-Support Supplement
Get calcium from food first; if you supplement, calcium citrate absorbs better than carbonate and is gentler without a meal. Keep total calcium (food + pills) around 1,000–1,200 mg/day — more doesn't help bone. Pair it with vitamin D3 and K2, which help calcium reach bone, and split doses to ~500 mg for better absorption.
Frequently Asked Questions
What is a T score in bone density?
A T-score compares your bone mineral density to the average for a healthy 30-year-old of the same sex. A T-score of 0 means your bone density equals the young adult average. Each -1.0 increment means your density is one standard deviation below that average — roughly 10-12% lower. T-scores above -1.0 are normal, -1.0 to -2.5 indicate osteopenia, and below -2.5 indicate osteoporosis.
What is a good T score for bone density?
A T-score above -1.0 is considered normal. Ideally, T-scores close to 0 indicate bone density near peak levels. A T-score between 0 and +1.0 is excellent. After menopause, maintaining a T-score above -1.0 is the goal — this requires active intervention (exercise, nutrition, and possibly hormone therapy) since the natural trajectory is downward.
What is a Z score in bone density?
A Z-score compares your bone density to the average for people of your same age and sex, rather than to young adult peak (which is what the T-score does). A Z-score of 0 means your bone density is average for your age. A Z-score below -2.0 means your bone density is significantly lower than expected for your age, suggesting an additional cause of bone loss beyond normal aging that should be investigated.
What is the bone density chart by age for females?
Average T-scores decline with age in women: age 40 (-0.2 to -0.5), age 50 (-0.5 to -1.0), age 55 (-1.0 to -1.5), age 60 (-1.2 to -1.8), age 65 (-1.5 to -2.2), age 70 (-1.8 to -2.5), age 80 (-2.0 to -3.0). The sharpest decline occurs between ages 50-60 during the menopausal transition, when 2-3% of bone density is lost annually due to estrogen withdrawal.
How is a bone density T-score calculated?
A T-score is calculated by comparing your bone mineral density (BMD, measured in g/cm²) to the average BMD of a healthy 30-year-old adult of the same sex — the "young-adult reference" — then expressing the difference in standard deviations from that average: T-score = (your BMD − young-adult mean BMD) ÷ young-adult standard deviation. A T-score of 0 means your BMD equals the young-adult average; each -1.0 represents one standard deviation below it, roughly a 10-12% lower BMD. The DEXA scanner's software calculates this automatically — you don't need to do the math yourself — but it explains why the same raw BMD reading can produce a different T-score on different machines, since each manufacturer uses its own reference database.
How often should I get a DEXA scan after menopause?
It depends mainly on your age and risk factors rather than menopause alone. Average-risk women are generally screened starting at 65, per USPSTF guidance, with rescreening about every 2 years after a normal result. Women with risk factors — early or surgical menopause, a family history of hip fracture, long-term corticosteroid use, or a prior fragility fracture — are often screened earlier, and rechecked on a similarly consistent schedule if the baseline already shows osteopenia.
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