A T-score is a number from a bone density test that tells you how your bone strength compares to that of a healthy 30-year-old adult. A score of -1 or higher is normal, -1 to -2.5 signals mild bone loss (osteopenia), and -2.5 or lower indicates osteoporosis. The World Health Organization established these cutoffs, and they remain the standard doctors use today.
How the T-Score Scale Works
Your T-score is measured in standard deviations, which is a statistical way of expressing how far your result falls from the average. A T-score of 0 means your bone density matches the average healthy young adult exactly. Each whole number below zero represents one standard deviation of bone loss. So a T-score of -2 means your bones are two standard deviations below what’s typical for a young, healthy person at peak bone mass.
The three categories are straightforward:
- Normal: T-score of -1.0 or above
- Osteopenia (low bone mass): T-score between -1.0 and -2.5
- Osteoporosis: T-score of -2.5 or below
A T-score of -2.5 is also a common threshold for starting medication. That said, doctors consider more than just the number. Your age, fracture history, family history, weight, smoking status, alcohol use, and whether you take certain medications like steroids all factor into treatment decisions.
How Bone Density Is Measured
The test that produces your T-score is called a DXA scan (sometimes written DEXA). It uses very low-dose X-rays to measure how dense your bones are at specific sites, typically the lower spine and the hip. These areas are chosen because they’re common fracture sites and give the most clinically useful picture of your skeletal health. The scan itself takes about 10 to 20 minutes, is painless, and requires no preparation.
If multiple sites are measured, your diagnosis is based on the lowest T-score among them. So if your spine comes back at -1.2 but your hip reads -2.6, the -2.6 is the number that determines your category.
Who Should Get Tested
The U.S. Preventive Services Task Force recommends routine bone density screening for all women aged 65 and older. Women younger than 65 who have increased risk factors should also be screened. Those risk factors include low body weight, a parent who fractured a hip, current smoking, heavy alcohol use (three or more drinks per day), rheumatoid arthritis, and long-term use of glucocorticoid medications.
For men, there isn’t enough evidence yet for the task force to make a blanket screening recommendation. In practice, many doctors will order a DXA scan for men over 70 or for younger men with clear risk factors like long-term steroid use or a history of fragility fractures.
T-Score vs. Z-Score
Your bone density report may also include a Z-score. While the T-score compares you to a healthy 30-year-old, the Z-score compares you to the average person of your same age, sex, and body size. For most postmenopausal women and men over 50, the T-score is the number that matters for diagnosis.
Z-scores become more important for premenopausal women, men under 50, and children. In these groups, some degree of bone loss relative to a 30-year-old may be expected, so a T-score could be misleading. A very low Z-score (typically -2.0 or below) in a younger person suggests something beyond normal aging is affecting bone health, such as a hormonal disorder, nutritional deficiency, or medication side effect.
When T-Scores Can Be Misleading
A T-score is useful but not perfect. It doesn’t always predict fracture risk accurately. Some people fracture bones despite having scores in the normal or osteopenia range, while others with low scores never fracture at all.
Certain conditions can also throw off the measurement. Spinal arthritis, for instance, can make a spine DXA reading look falsely normal because the extra bone growth from arthritis inflates the density number. People with naturally small skeletal frames may have lower T-scores that reflect their body type rather than true bone disease. And the scan measures density at only a few sites, so it can miss problems elsewhere in the skeleton.
This is why clinicians often use fracture risk calculators that combine the T-score with other clinical factors. The goal isn’t just to label your bones as normal or not, but to estimate your actual chance of breaking a bone in the next 10 years and decide whether treatment would meaningfully reduce that risk.
What Different Scores Mean in Practice
If your T-score is in the normal range, your bones are in good shape. The focus at that point is maintaining bone health through weight-bearing exercise, adequate calcium and vitamin D intake, and avoiding smoking.
A score in the osteopenia range means you’ve lost some bone mass but haven’t crossed into osteoporosis. Most people with osteopenia won’t need medication right away. Lifestyle changes are typically the first recommendation, along with a follow-up DXA scan in one to two years to see whether bone loss is progressing.
A score of -2.5 or lower generally warrants a conversation about treatment, especially if you have additional risk factors or have already had a fracture from a minor fall or bump (called a fragility fracture). In some cases, a fragility fracture alone is enough to diagnose osteoporosis and start treatment regardless of the T-score number.