Free Testosterone Test
A free testosterone test measures the unbound portion of testosterone in the blood — the fraction generally described as available to the body's tissues. Clinicians use it to help evaluate the available portion of the hormone, often alongside total testosterone.
About this test
Most testosterone in the blood is bound to proteins — a large share to sex hormone-binding globulin, or SHBG, and some to albumin — while only a small fraction moves freely. A free testosterone test looks specifically at that unbound fraction, the portion typically considered available to interact with tissues.
The test is done with a routine blood draw at a patient service center. A phlebotomist collects a sample from a vein, usually in the arm, and sends it to the laboratory.
Test details
| Quest code | 18944 |
|---|---|
| Methodology | Chromatography/Mass Spectrometry • Calculation • Immunochemiluminescence Assay |
| Sample type | 2.8 mL serum |
| Collection | Quest patient service center |
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Additional details
What this test looks at
The free testosterone test focuses on the unbound fraction of the hormone rather than the total amount. Because carrier proteins like SHBG hold most testosterone, the freely circulating portion is small, but it is the part some clinicians want to see directly when the bound and unbound portions may not be tracking together.
It also helps to know what the test does not show: it does not describe the entire pool of testosterone, which is what total testosterone captures. That distinction is exactly why free testosterone is often read together with the total rather than on its own.
How it's often used with other tests
Free testosterone is frequently paired with total testosterone, and sometimes with SHBG, so a clinician can see how the available fraction relates to the whole pool and to the carrier protein that shapes it. Read together, these markers offer a fuller sense of testosterone status than any single one on its own.
Depending on the situation, a clinician may consider additional hormone markers to build a broader picture. The value of the free fraction lies in the context it adds, which is why it is usually interpreted as part of a set rather than in isolation.
Order online and a physician order is included — no doctor's visit and no insurance needed. Your sample is collected at a Quest Diagnostics patient service center.
Laboratory results should always be interpreted by a licensed clinician who knows your health history. This page is information about a test, not medical advice.
Frequently asked questions
What does a free testosterone test measure?
It measures the unbound portion of testosterone in the blood — the fraction generally described as available to the body's tissues. This is a smaller, more specific slice than total testosterone, which counts the whole pool.
How is it different from a total testosterone test?
Total testosterone counts all the hormone in the blood, including the portion bound to proteins. A free testosterone test measures only the unbound, available fraction. Clinicians often review both together for a fuller picture.
How is the sample collected?
Through a routine blood draw at a patient service center. A phlebotomist takes a small sample from a vein in the arm and sends it to the laboratory. Morning collection is common because testosterone varies through the day.
Is free testosterone measured directly?
It depends on the laboratory. Some measure it directly, while others estimate it from total testosterone and SHBG. The method can affect interpretation, which is one reason a clinician reads the result in context.
Does this test diagnose low testosterone?
No single test diagnoses a condition. A free testosterone result is one piece of information a clinician weighs together with symptoms, age, history, and other markers before drawing any conclusions.
How much is a Testosterone, Free test?
$149, paid once at checkout. The price includes the physician's order this test requires and sample collection at a Quest patient service center.