Skip to content

Testosterone, Free (Serum)

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

This test measures the amount of free (unbound) testosterone in your blood. Free testosterone is the active form of the hormone that your body uses.

Quick summary

["Free testosterone helps regulate sex hormones and supports overall health, including energy and mood."]

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

Key facts at a glance

LOINC
100793-9
Short code
Testost Fld-mCnc
Synonyms
Testost Fld-mCnc
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 Is This Test Done?

Your healthcare provider may order this test to evaluate hormone balance, especially if you have symptoms like low libido, irregular menstrual cycles, or signs of hormonal imbalances. It can also help diagnose conditions like polycystic ovary syndrome (PCOS), infertility, or hormonal disorders.

What Does a Low or High Result Mean?

Results can vary based on age, sex, and health status. Low free testosterone may indicate hormonal deficiencies or conditions affecting hormone production, while high levels could signal tumors or other metabolic issues. Your provider will interpret results in the context of your symptoms and medical history.

How Is This Test Performed?

A blood sample is drawn from a vein in your arm. The sample is sent to a lab where it is processed to measure free testosterone levels using a sensitive immunoassay method.

What Should You Do Before the Test?

Avoid smoking, alcohol, or strenuous exercise 24 hours before the test. Some medications (like steroids or birth control) may affect results, so discuss them with your provider.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance: Free testosterone is crucial for sexual development, reproductive function, and bone/muscle health. Abnormal levels may signal underlying conditions requiring further evaluation, such as thyroid disorders, adrenal issues, or genetic syndromes.

Short name

Free Testosterone

Frequently asked questions

How often should I get this test?
The frequency depends on your symptoms, medical history, and reasons for testing. Your provider will determine the best schedule for you, often every 6–12 months for monitoring.
Does diet or supplements affect free testosterone levels?
Certain foods (like zinc-rich or healthy fats) and supplements (e.g., vitamin D, magnesium) may support hormone balance, but they don’t directly alter free testosterone levels. Always check with your provider before starting new supplements.
Can stress or sleep affect my test results?
Yes, chronic stress or poor sleep can temporarily lower testosterone levels. Avoiding extreme stress or ensuring good sleep hygiene before testing may help provide more 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