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Serum or Plasma Free Testosterone (Concentration)

Published: August 9, 2026Updated: August 17, 2026

This test measures the amount of free (unbound) testosterone in your blood, which is the form that actively contributes to hormone function.

Quick summary

["Free testosterone reflects your biologically available hormone level for reproductive and metabolic health."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
90123-1
Short code
RESPONSETEAMLEADERNAME
Synonyms
—
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
17
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 Is This Test Done?

Your healthcare provider may order this test to evaluate hormone balance, especially if you have symptoms like low libido, irregular periods, or infertility. It’s also used in conditions like polycystic ovary syndrome (PCOS) or hormone-related cancers.

Who Might Need This Test?

Men and women with suspected hormone imbalances, such as those experiencing unexplained fatigue, mood changes, or reproductive issues, may undergo this test. It’s sometimes included in comprehensive hormone panels.

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 for blood collection.

What Happens During the Test?

A healthcare professional will draw blood from a vein in your arm. The sample is sent to a lab for analysis of free testosterone levels.

Reference range

NCBI: NSE 0-17 ng/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Free testosterone is critical for muscle mass, bone density, and sexual health. Low levels may indicate conditions like hypogonadism, while high levels could signal tumors or Cushing’s syndrome.

Short name

Free Testosterone

Frequently asked questions

What does a ‘normal’ result mean?
Results are compared to your individual baseline and clinical context rather than a single reference range. Your provider will interpret the result in relation to your symptoms and medical history.
Does fasting affect this test?
Yes, fasting may influence hormone levels, so follow your provider’s instructions for optimal accuracy. Non-fasting results may require additional testing.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Follow-up with your provider to discuss findings.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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 17, 2026. · Read our editorial policy