Testosterone, Serum Free (Mass Concentration)
This test measures the amount of free (unbound) testosterone in your blood, which is the form available to your body’s tissues.
["Free testosterone reflects biologically active levels of this hormone, important for health and symptoms."]
Key facts at a glance
- LOINC
- 111384-4
- Short code
- Testost Free Msmt SerPl
- Synonyms
- Testost Free Msmt SerPl
- 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 This Test Matters
Free testosterone is a key measure of your body’s active hormone levels, separate from total testosterone. It’s particularly relevant for conditions affecting hormone balance, such as infertility, hormonal imbalances, or symptoms of low testosterone.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before your blood draw if your doctor specifies it. Wear comfortable clothing and plan to rest after the draw.
How the Test Works
Blood is drawn from a vein, typically in your arm. The sample is processed to isolate free testosterone, which is then measured using a sensitive immunoassay technique to detect its presence.
Possible Reasons for Testing
Your doctor may order this test to evaluate symptoms like low libido, fatigue, or irregular menstrual cycles. It’s also used in fertility assessments, hormone replacement planning, or monitoring conditions like polycystic ovary syndrome (PCOS).
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 activity. Low levels may signal hormonal deficiencies, while elevated levels could point to conditions like Cushing’s syndrome or tumors. Always discuss results with your healthcare provider.
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your doctor will contact you to review findings and next steps.
Standard fasting guidelines apply (e.g., no food for 8–12 hours), but check with your lab or doctor for specific instructions. Water is usually allowed unless otherwise noted.
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