Skip to content

Serum/plasma free testosterone concentration

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of free (unbound) testosterone in your blood, which is the active form of the hormone that helps regulate male and female sex characteristics.

Quick summary

["Free testosterone helps balance hormone levels and supports reproductive health."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
79176-4
Short code
GH 30M p chal SerPl-aCnc
Synonyms
GH 30M p chal SerPl-aCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
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 This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms of hormonal imbalances, such as low libido, fatigue, or changes in body hair. It could also be used to monitor conditions like hypogonadism (low testosterone) or to check for Cushing’s syndrome or other hormonal 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 blood draw if your test involves a fasting sample. Avoid smoking or consuming alcohol for 24 hours before testing.

How the Test Works

Blood is drawn from a vein, usually in your arm. The sample is then processed to separate free testosterone from other proteins in the blood. The test measures the unbound fraction, which is biologically active.

What the Results Mean

Results are compared to reference ranges based on age, sex, and health status. Low levels may indicate hormonal deficiencies, while high levels could suggest conditions like polycystic ovary syndrome (PCOS) or tumors.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Free testosterone levels are critical for diagnosing and managing hormonal disorders. Low levels may require treatment with hormones or further evaluation for underlying causes like pituitary issues or genetic conditions. High levels may prompt investigation into conditions affecting hormone production or metabolism.

Short name

Free testosterone

Frequently asked questions

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.
What causes free testosterone levels to change?
Changes can occur due to age, medications (e.g., steroids), chronic illnesses, or lifestyle factors like obesity or smoking. Hormonal imbalances, thyroid disorders, or genetic factors may also influence results.
Is fasting required for this test?
No fasting is required unless specified by your provider. However, avoid alcohol and smoking for 24 hours before testing to ensure accurate results.
  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 16, 2026. · Read our editorial policy