Free testosterone (serum/plasma)
This test measures the amount of free (unbound) testosterone in your blood, which is the active form of the hormone responsible for male and female sex characteristics, muscle development, and overall health.
["Free testosterone helps assess hormone balance and potential issues with testosterone levels, especially in conditions like hypogonadism or hormonal imbalances."]
Key facts at a glance
- LOINC
- 49043-3
- Short code
- Testost Free MFr SerPl DL<=1.0 ng/dL
- Synonyms
- Testost Free MFr SerPl DL<=1.0 ng/dL
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0
- Ref high
- 100
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- detection-limit-ng-dl
- CPT
- 83721
- SNOMED
- 113079007
- 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 diagnose or monitor conditions affecting hormone levels, such as low testosterone (hypogonadism), polycystic ovary syndrome (PCOS), or other endocrine disorders. It can also help evaluate symptoms like low libido, fatigue, or irregular menstrual cycles in adults of both genders.
What to Expect Before the Test
No special preparation is needed for this blood test. You may have it drawn at any time of day, but some conditions (like certain medications) might affect results. Always inform your provider about all medications, supplements, or recent illnesses.
What Happens During the Test?
A healthcare professional will collect a blood sample from a vein in your arm using a small needle. You may feel a slight pinch, but the procedure is quick and typically painless. The sample is then sent to a lab for analysis.
What Are the Results Meaning?
Results are compared to general reference ranges for free testosterone, which can vary slightly by lab and age. Low levels may indicate hormonal imbalances, while very high levels could suggest conditions like Cushing’s syndrome or tumors. Your provider will interpret results in the context of your overall health and symptoms.
Reference range
Optimal: <100 mg/dLN/A
Fasting for 12-14 hours preferred. Water is permitted. Avoid alcohol for 24 hours before the test.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Free testosterone is crucial for maintaining energy, muscle mass, and reproductive health. Abnormal levels can signal underlying conditions that require medical attention, such as hormonal deficiencies, tumors, or metabolic disorders. Regular monitoring may be needed if you have conditions like PCOS, adrenal disorders, or are taking medications that affect hormone levels.
Short name
Free testosterone
Frequently asked questions
What does a free testosterone test measure?
Why is free testosterone important?
Can lifestyle factors affect free testosterone results?
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