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Serum or plasma concentration of free (unbound) testosterone

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

This test measures the amount of free (not protein-bound) testosterone in your blood. Free testosterone is the active form that your body uses.

Quick summary

["Understanding your free testosterone levels helps assess hormonal balance, especially in conditions like low testosterone or fertility issues."]

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

Key facts at a glance

LOINC
11929-7
Short code
GA from GSD.Rempen91
Synonyms
GA from GSD.Rempen91
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-estimated-from-gsd-rempen
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 Is Done

Your healthcare provider may order this test if you have symptoms like low energy, low sex drive, or irregular menstrual periods. It’s also used in fertility evaluations, hormone replacement therapy planning, or monitoring conditions like polycystic ovary syndrome (PCOS).

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 uses a specific method. Avoid smoking or drinking alcohol for 24 hours before testing.

During the Test

A small needle will draw blood from a vein in your arm. You may feel a slight pinch, but the process is quick. The blood sample is sent to a lab for analysis.

What the Results Mean

Results are compared to general reference ranges for free testosterone, but individual needs vary. High levels may indicate hormonal imbalances or tumors, while low levels could signal conditions like hypogonadism or Cushing’s syndrome.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free testosterone level

Frequently asked questions

What causes free testosterone levels to be too low?
Low free testosterone can result from conditions like hypogonadism (low testosterone production), pituitary disorders, or chronic illnesses. It may also be affected by medications (e.g., steroids) or genetic factors.
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 if you have questions about your results.
Can lifestyle changes affect free testosterone levels?
Yes, diet, exercise, sleep, and stress levels can influence testosterone. Maintaining a healthy weight, reducing alcohol, and managing chronic stress may support balanced hormone levels.
  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