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Serum/plasma mass concentration of free (unbound) testosterone

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

This test measures the amount of free testosterone in your blood, which is the form of testosterone that actively affects hormones and health.

Quick summary

["Free testosterone helps balance hormone levels and supports overall health, especially in men and women."]

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

Key facts at a glance

LOINC
2857-1
Short code
PSA SerPl-mCnc
Synonyms
PSA SerPl-mCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
4
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
84153
SNOMED
39392002
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 hormone imbalances, such as low libido, fatigue, or changes in body hair. It could also be part of evaluations for conditions like hypogonadism, infertility, or 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 draw if your lab uses a specific method. Wear a comfortable shirt for easy access to your arm.

What Happens During the Test

A healthcare professional will draw blood from a vein in your arm. The blood will be sent to a lab to separate serum or plasma, where the free testosterone level is measured using a sensitive analytical method.

What the Results Mean

Results are compared to general reference ranges for free testosterone, but individual needs vary. Low levels may indicate hormone deficiencies, while very high levels could signal conditions like Cushing’s syndrome or tumors.

Reference range

Normal: <4.0 ng/mLN/A

Specimen: serum

No special preparation required. For PSA, avoid sexual activity for 24-48 hours before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free testosterone level

Frequently asked questions

How does free testosterone differ from total testosterone?
Free testosterone is the biologically active form of testosterone that circulates unbound in your blood. Total testosterone includes both free and protein-bound forms, so free levels provide a clearer picture of hormone activity. If your provider mentions total testosterone, ask how free levels might differ in your case.
What if my results are outside the normal range?
If your free testosterone is low, your doctor may recommend further testing (like LH/FSH levels) or treatments like hormone therapy. If high, they could investigate causes like tumors or medication side effects. Always discuss results with your provider—they’ll interpret them in the context of your health.
Can lifestyle changes affect free testosterone?
Yes! Exercise, a balanced diet, and avoiding smoking or excessive alcohol can support healthy hormone levels. Stress management and maintaining a healthy weight also play a role, though this test alone doesn’t show direct lifestyle impacts—it’s part of a broader evaluation.
  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