Prostate-Specific Antigen, Free (fPSA)
Free PSA measures the fraction of prostate-specific antigen that circulates unbound to other proteins in your blood. It is usually reported together with total PSA to give a more detailed picture of prostate health.
When total PSA sits in a borderline range, free PSA can add helpful context and is often used to refine the picture rather than stand alone. It matters mainly as one piece of information your clinician weighs when deciding whether closer evaluation is needed. On its own it is not a diagnostic test.
Free PSA is generally interpreted as a ratio to total PSA rather than in isolation, so a single free-PSA number in one direction or another is hard to read by itself. The same benign factors that affect total PSA, such as an enlarged prostate, inflammation, or recent activity, also influence this value. This is not a diagnosis, and your clinician will consider the full panel and your history.
Because free PSA is meaningful mostly in relation to total PSA, a given value is best understood through that ratio and your overall clinical picture rather than as a standalone reassuring or concerning result.
There is no single free-PSA target that applies to everyone; its value comes from the free/total ratio and your individual context. A clinician should interpret it alongside your total PSA and personal risk factors.
Sources
- Prostate-Specific Antigen (PSA) Test - National Cancer Institute
- PSA (Prostate-Specific Antigen) Test - MedlinePlus
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.