Total Serum Testosterone (Free)
This test measures the amount of free (unbound) testosterone in your blood, which is the active form of this hormone that your body uses.
["Free testosterone helps regulate energy, mood, and reproductive health in both men and women."]
Key facts at a glance
- LOINC
- 108779-0
- Short code
- Testosterone.free+WB Msmt SerPl
- Synonyms
- Testosterone.free+WB Msmt SerPl
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 300
- Ref high
- 1000
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 84403
- SNOMED
- 33790003
- 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 Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms like low libido, fatigue, irregular periods (in women), or unexplained hair loss. It could also be part of an evaluation for hormonal imbalances, fertility issues, or conditions like polycystic ovary syndrome (PCOS) or hypogonadism.
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 provider specifies it. Wear a loose shirt for easy access to your vein.
What the Test Involves
A healthcare professional will insert a small needle into your arm to draw blood. You may feel a brief pinch, but it usually doesn’t cause discomfort afterward. The blood sample is sent to a lab for analysis.
What the Results Mean
Results are compared to general reference ranges, but your specific range may vary based on age, sex, and health status. Low levels may indicate hormonal deficiencies, while very high levels could signal conditions like Cushing’s syndrome or tumors.
Reference range
Adult males: 300-1000 ng/dLN/A
For females: inform if menstrual cycle status. For certain tests, timing within menstrual cycle may matter.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Free testosterone level
Frequently asked questions
Low free testosterone levels can affect energy, muscle mass, and sexual function. In women, it may contribute to symptoms like hot flashes or infertility. High levels could signal underlying endocrine disorders or medication side effects, requiring further evaluation.
Free testosterone is the portion of testosterone that is unbound to proteins in the blood and thus biologically active. Total testosterone includes both free and protein-bound forms, so free levels give a clearer picture of your hormone’s direct impact on the body.
Yes, lifestyle factors like diet (e.g., high-fat or low-carb diets), exercise, sleep, and stress can influence testosterone levels. Maintaining a balanced diet, regular physical activity, and good sleep hygiene may support healthy hormone function.
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