Serum or plasma mass concentration of free (unbound) testosterone
This test measures the amount of free testosterone in your blood, which is the form that actively contributes to hormone function. Free testosterone is not bound to proteins and is available to your body’s tissues.
["Understanding your free testosterone levels helps assess hormone balance, especially in conditions affecting sex hormones."]
Key facts at a glance
- LOINC
- 53222-6
- Short code
- Fact XI PPP-aCnc
- Synonyms
- Fact XI PPP-aCnc
- Category
- chemistry
- Sample
- plasma
- Container
- Lavender-top (EDTA) or Green-top (Heparin)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- coag
- 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 for Your Health
Free testosterone is a critical measure because it reflects the biologically active portion of testosterone in your blood. While total testosterone includes both free and bound forms, free testosterone is directly linked to reproductive health, muscle mass, and energy levels. Abnormal levels may signal conditions like hypogonadism (low testosterone) or Cushing’s syndrome (high cortisol-related suppression).
How the Test Works
This test uses a blood sample drawn from a vein. The lab separates the serum or plasma and applies a specialized method (likely immunoassay or mass spectrometry) to quantify free testosterone without interference from protein-bound forms. Results are expressed in mass concentration units.
Common Reasons for Testing
Doctors may order this test to evaluate symptoms like low libido, fatigue, or infertility in men and women. It’s also used in fertility assessments, hormone replacement therapy monitoring, and diagnosing conditions affecting sex hormone metabolism.
Preparation Tips
No special preparation is needed, but avoid smoking or alcohol for 24 hours before the test. Fasted or non-fasted samples are typically acceptable, but check with your provider for any specific instructions related to your condition.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free testosterone levels help diagnose or monitor conditions like: - Hypogonadism (low testosterone), - Polycystic ovary syndrome (PCOS) in women, - Cushing’s syndrome (high cortisol-related suppression), - Androgen insensitivity syndromes. Abnormal results may prompt further testing for underlying causes, such as pituitary disorders or adrenal gland issues.
Short name
Free testosterone level
Frequently asked questions
What Does a Low Free Testosterone Level Mean?
What Does a High Free Testosterone Level Mean?
How Often Should I Get This Test?
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