Free Prostate-Specific Antigen
Hormones marker
Free PSA
Free Prostate-Specific Antigen
The unbound (free) fraction of prostate-specific antigen circulating in serum. Total PSA exists in two main forms: complexed PSA (bound to plasma proteins, mostly alpha-1-antichymotrypsin) and free PSA (unbound). Free PSA is most useful when interpreted alongside total PSA as the percent free PSA ratio (see `psa-free-percent`). Reflexed by many labs when total PSA is in the 4 to 10 ug/L grey zone.
PED Notes
Free PSA on its own has limited interpretation; what matters clinically is the ratio of free to total PSA (percent free PSA). The reflex Free PSA test is typically ordered when total PSA falls in the 4 to 10 ug/L diagnostic grey zone, where the free / total ratio helps distinguish benign prostatic hyperplasia (BPH) from prostate cancer. Bodybuilders on DHT-derivative AAS (Masteron, Primobolan, Anavar, Winstrol, Proviron) and high-dose testosterone often see total PSA elevation; in this context a Free PSA reflex test plus the percent free ratio can help separate PED-driven prostatic stimulation from cancer-suspicious patterns. Free PSA itself is not a screening test.
Free PSA is interpreted only in conjunction with Total PSA. The clinically useful number is the ratio (percent free PSA), not the absolute Free PSA value.
When and why it is ordered:
- Reflex test when Total PSA is in the 4 to 10 ug/L grey zone (some labs use 2.5 to 10)
- The ratio of Free PSA to Total PSA (percent free PSA) helps distinguish prostate cancer from BPH
- Lower percent free PSA (typically <25%) carries higher cancer risk
- Higher percent free PSA (>25%) suggests BPH is more likely than cancer
Interpretation framework (use percent free PSA):
- See
psa-free-percentfor the actionable ratio and its cutoffs - Free PSA alone, in absolute terms, has no direct decision value
For PED users:
- DHT derivatives stimulate prostate tissue and can elevate Total PSA without being malignant
- A Free PSA reflex with high percent free (>25%) reassures that the elevation pattern looks more BPH-like
- A Free PSA reflex with low percent free (<10%) is concerning regardless of PED context and warrants urology referral
History Chart
Reading History
Frequently Asked Questions
Reference Ranges
Standard Range
VitalMetrics Range