What this marker measures
Free PSA is typically only ordered when total PSA sits in a borderline range. It is interpreted as a percentage of total PSA (the "% free PSA"), not as a standalone number.
High or low: what it can mean
High Free PSA
A higher free PSA fraction (i.e. a high free-to-total ratio) is generally more reassuring in the context of an elevated total PSA. The absolute number on its own is less informative than the ratio.
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Low Free PSA
A lower free PSA fraction may prompt a clinician to look more closely at prostate findings, especially when total PSA is also elevated. As with every PSA value, this is a starting point for a conversation, not a diagnosis.
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Frequently asked questions
What is Free PSA?
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Free PSA is the fraction of PSA in blood that is NOT bound to other proteins. It is ordered alongside total PSA to refine interpretation — the ratio of free to total PSA is what clinicians typically discuss.
What does Free PSA measure?
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Free PSA is typically only ordered when total PSA sits in a borderline range. It is interpreted as a percentage of total PSA (the "% free PSA"), not as a standalone number.
What does high Free PSA mean?
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A higher free PSA fraction (i.e. a high free-to-total ratio) is generally more reassuring in the context of an elevated total PSA. The absolute number on its own is less informative than the ratio.
What does low Free PSA mean?
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A lower free PSA fraction may prompt a clinician to look more closely at prostate findings, especially when total PSA is also elevated. As with every PSA value, this is a starting point for a conversation, not a diagnosis.
Related biomarkers
Editorial note
LabTestly explains lab markers using plain-English educational content. Reference ranges may vary by laboratory and should be interpreted with a clinician.
Educational content · Editorially reviewed for clarity · Last updated
Common sources used for lab-test education
Not medical advice
This page is for general understanding only and does not replace medical advice from your clinician. Reference ranges can vary by laboratory, age, sex, pregnancy status, medications, and clinical context.