Testosterone, Free (Serum)
This test measures the amount of free (unbound) testosterone in your blood. Free testosterone is the active form of the hormone that can easily enter cells to influence growth, development, and reproductive functions.
["Free testosterone helps regulate energy, mood, and sex drive."]
Key facts at a glance
- LOINC
- 17688-3
- Short code
- Testost 1.5h p chal SerPl-mCnc
- Synonyms
- Testost 1.5h p chal SerPl-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why Is This Test Done?
Your healthcare provider may order a free testosterone test to evaluate hormonal imbalances, diagnose conditions like hypogonadism (low testosterone), or assess symptoms such as low libido, fatigue, or irregular menstrual cycles. It can also help monitor treatment effectiveness for hormone-related disorders.
Who Might Need This Test?
Men and women with suspected hormonal issues—such as unexplained low energy, changes in libido, or reproductive problems—may undergo this test. It’s also sometimes checked in people with conditions like polycystic ovary syndrome (PCOS) or those undergoing hormone therapy.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the blood draw if your test involves fasting-related measurements. Wear comfortable clothing and plan to rest afterward, as drawing blood can cause lightheadedness.
What Happens During the Test?
A healthcare professional will insert a needle into a vein in your arm to collect a small amount of blood. The process usually takes a few minutes, and you’ll feel a brief pinch. The blood sample is then sent to a lab for analysis.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Free Testosterone
Frequently asked questions
Free testosterone levels can indicate whether your body is producing adequate hormone levels. Low free testosterone may signal conditions like pituitary disorders, adrenal insufficiency, or aging-related changes. High levels could suggest hormonal imbalances, tumors, or certain medications affecting hormone metabolism.
How long will results take?
What do my results mean?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy