DEXA, T-Score, Z-Score
DEXA tells you what your skeleton actually weighs
DEXA (Dual-Energy X-ray Absorptiometry) measures bone mineral density — the gold-standard test for osteoporosis screening. Same scan can also report body composition (muscle mass, visceral fat). Roughly $50–250 in most regions, ~5 minutes, minimal radiation (<1/10 a chest X-ray).
T-score vs Z-score — which to read
T-score compares your bone density to a HEALTHY YOUNG ADULT (the peak). Z-score compares you to your AGE PEERS. Diagnostic thresholds use T-score: above −1.0 normal, −1.0 to −2.5 osteopenia, below −2.5 osteoporosis. Z-score matters mainly for younger adults or to flag unusual age-relative loss.
When to start scanning
USPSTF recommends DEXA at 65+ for women (or earlier with risk factors). Men under-screened in standard practice — the European Endocrine Society recommends 70+ or earlier with risk factors. Longevity-practice norm: baseline DEXA at 50–55, repeat every 2–5 years if normal, sooner if abnormal.
TBS — when T-score lies
Trabecular Bone Score (TBS) is a texture analysis layered onto a standard DEXA scan that reads the microarchitecture of the lumbar spine. Two people can have identical T-scores but very different fracture risk if their underlying bone is dense-but-fragile vs less-dense-but-resilient. TBS catches that mismatch — particularly useful in diabetics and chronic-glucocorticoid users whose bone density looks fine but architecture has degraded. Ask your provider for TBS on follow-up DEXAs.
Order T-score bands by severity
From healthiest to most severe.
Key Takeaway
DEXA is one of the highest-leverage low-cost tests in longevity medicine. Get a baseline at 50–55 — earlier with risk factors. The T-score is your personal trajectory marker and tells you whether to lean harder on resistance training, vitamin D + calcium + K2, and HRT discussions. Add TBS on follow-ups to catch the mismatch between bone density and architecture.