What is % Free PSA?
The % free PSA is the proportion of total PSA that is not bound to other proteins. It is calculated as (free PSA ÷ total PSA) × 100 and is the clinically useful number when free PSA is ordered.
Cutoffs for % free PSA vary by lab, guideline body, and clinical context — there is no single universally-accepted threshold. The printed lab range and a conversation with a clinician are the right place to interpret this number.
Why might % Free PSA be high?
A higher % free PSA (e.g. >25%) is generally considered reassuring when total PSA is borderline. It does not rule anything out — it is one of several inputs a clinician weighs.
This information is educational. A single out-of-range result is rarely the whole picture — a healthcare professional can interpret your numbers alongside your overall health and history.
Context questions that matter
- →Was this result slightly or clearly outside the reference range?
- →Were related markers also high or low?
- →Is this new compared with previous tests?
- →Could recent illness, exercise, fasting, alcohol, supplements, or medication affect it?
- →Do you have symptoms that should be discussed with a clinician?
Questions to ask your doctor
- →Could time of day, cycle phase, stress, sleep, medication or supplements affect this result?
- →How does this compare with related hormones such as LH, FSH, testosterone, estradiol, prolactin, cortisol or DHEA-S?
- →Is this a one-time result, or part of a pattern that needs repeat testing?
Don't guess from one flagged result.
Start with the most relevant panel and see how your markers fit together in plain English.
Frequently asked questions
What does high % Free PSA mean?
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A higher % free PSA (e.g. >25%) is generally considered reassuring when total PSA is borderline. It does not rule anything out — it is one of several inputs a clinician weighs.
What is % Free PSA?
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The % free PSA is the proportion of total PSA that is not bound to other proteins. It is calculated as (free PSA ÷ total PSA) × 100 and is the clinically useful number when free PSA is ordered.
Does timing matter for hormone tests?
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Often yes. Time of day, menstrual cycle phase, sleep, acute stress, medications and supplements can all affect hormone results. Morning samples and same-time-of-day repeat testing are typically preferred for hormones with a daily rhythm.
Should hormone results be compared with related hormones?
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Yes — hormones are usually interpreted as patterns. TSH is read with Free T4 and Free T3; testosterone is read with LH, FSH and SHBG; cortisol is read with ACTH and the time of day. Single values out of context can be misleading.