Serum/plasma free testosterone concentration
This test measures the amount of free (unbound) testosterone in your blood, which is the biologically active form of the hormone.
["Free testosterone helps regulate energy, mood, and sexual health in both men and women."]
Key facts at a glance
- LOINC
- 25946-5
- Short code
- LH sp4 p chal SerPl IRP1-aCnc
- Synonyms
- LH sp4 p chal SerPl IRP1-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 1.5
- Ref high
- 9
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- st-irp
- CPT
- 83002
- 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 this test to evaluate hormonal balance, diagnose conditions like low testosterone (hypogonadism), or assess symptoms such as fatigue, low libido, or irregular menstrual cycles. It can also help monitor treatment for hormone-related disorders.
What to Expect Before the Test
No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your lab requires it. Wear comfortable clothing and plan to rest during the blood draw.
What Happens During the Test?
A healthcare professional will draw blood from a vein in your arm. You may feel a slight pinch, but the process usually takes only a few minutes. The blood sample is sent to a lab for analysis.
What to Expect After the Test
You can resume normal activities immediately. There may be mild bruising or soreness at the injection site, but this usually fades within a day or two. Follow-up instructions from your provider will guide next steps.
Reference range
Follicular: 1.5-9.0 mIU/mLN/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.
Free testosterone levels can indicate hormonal imbalances affecting energy, muscle mass, or reproductive health. Low levels may suggest conditions like hypogonadism, while high levels could signal tumors or other endocrine disorders. Results are interpreted in context with symptoms and other tests.
Short name
Free testosterone
Frequently asked questions
How long does it take to get results?
What does a low or high free testosterone level mean?
Can lifestyle changes affect free testosterone levels?
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