free testosterone (ria)
Reproductive EndocrinologyBlood sampleResults 3-5 daysNo fasting
Free Testosterone (RIA)
Free testosterone is the active portion of testosterone not bound to proteins. This test measures that free fraction in your blood.
Sample
Blood
Results
3-5 days
Fasting
Not required
Follow-up
Optional add-on
What this test detects
Free Testosterone
RIA · serum
Quantitative · pg/mL
When to get this test
Low testosterone symptoms
Helps assess low libido, fatigue, or reduced muscle mass when total testosterone is borderline.
PCOS and excess androgens
In women, helps evaluate acne, excess hair growth, or irregular periods.
Detailed hormone picture
Adds information when binding proteins may be affecting total testosterone results.
How to prepare
01
Morning sample is preferred.
Common questions
How is free testosterone different from total testosterone?
Total measures all testosterone, while free measures only the active portion not bound to proteins. The free fraction can give extra insight when results are borderline.
Why a morning sample?
Testosterone is usually highest in the morning, so a morning sample gives a more consistent reading.