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Hormone health

Free Testosterone

Also known as: Free T test, Unbound testosterone test, Bioactive testosterone test (free fraction)

Testosterone is vital for women’s health — the hormone supports muscle strength, bone density, cognitive function, and sexual desire. The free testosterone test measures the fraction of testosterone in your blood that’s not bound to proteins like sex-hormone binding globulin (SHBG) or albumin. In other words, it measures the hormone that’s actually active and available for your body to use.

Doctors examine free testosterone levels to get a clearer picture of your hormonal health, especially in the presence of symptoms like fatigue, low sex drive, hair loss, or irregular cycles. Because free testosterone reflects the hormone’s active role in the body, it’s one of the best ways to understand how well your androgen system is working.

There are a couple of ways you can measure your free testosterone levels:

  • Direct measurement. Specialized assays, such as equilibrium dialysis, directly measure free testosterone.

  • Calculated free testosterone. Providers can estimate free testosterone levels by using formulas that incorporate total testosterone and SHBG levels.

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Key takeaways

  • Sample required: Blood

  • Tests for: The biologically active fraction of testosterone in blood that is not bound to proteins like SHBG or albumin

  • Healthy range: 0.0–4.2 picograms per milliliter (pg/mL)

What can a free testosterone test tell you?

Free testosterone testing helps to clarify androgen activity. Providers may order it to:

What is being tested?

In women, the adrenal glands and ovaries are the primary producers of testosterone. Most testosterone travels through the blood attached to proteins like SHBG and albumin, but a small fraction — about 2-3 percent — circulates freely. This free testosterone is the portion that can enter cells and activate androgen receptors, influencing everything from muscle tone and bone strength to energy, mood, and sexual health.

Balanced levels of free testosterone can contribute to your general vitality and help to keep your metabolism and reproductive system running smoothly. Excess testosterone can disrupt ovulation and cause acne or unwanted hair growth, while low levels can lead to low libido, fatigue, and reduced muscle mass.

Because free testosterone reflects the hormone’s biologically active form, the test offers one of the clearest views into how your androgen system is functioning.

Where is the free testosterone test typically included?

Free testosterone is not part of general health panels like the basic metabolic panel (BMP) or comprehensive metabolic panel (CMP). It is commonly included in the following workups:

  • Expanded hormone panels. Along with total testosterone, SHBG, estradiol, follicle-stimulating hormone (FSH), and prolactin.

  • PCOS investigations. Often with estradiol, progesterone, FSH, DHEA, and SHBG to evaluate androgen excess.

Who should get a free testosterone test?

A provider may order free testosterone testing if you have symptoms of androgen excess, such as acne, excess facial or body hair, scalp hair thinning, irregular or absent menstrual cycles, or fertility issues.

A provider may also order free testosterone as part of an expanded hormone panel to investigate low androgen levels, especially during perimenopause or after menopause.

Results of a free testosterone test can shed light on conditions linked to abnormal androgens, such as PCOS, congenital adrenal hyperplasia, rare ovarian or adrenal tumors, or Cushing’s syndrome.

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Not available in all 50 states. Eligibility and provider order required. Lab results alone are not intended to diagnose, treat, or cure any condition. A provider will reach out about critical results and plans include access to 24/7 provider messaging.

Images for illustrative purposes only.

Frequently asked questions

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What causes changes in free testosterone levels?

Free testosterone can shift due to aging, certain medications, and lifestyle factors.  

High free testosterone may be associated with PCOS, congenital adrenal hyperplasia, Cushing’s syndrome, androgen-secreting ovarian or adrenal tumors (rare), and low SHBG (related to obesity or insulin resistance). Factors that can increase free testosterone include certain forms of hormone replacement therapy, stress and anxiety, and resistance exercise.

Low free testosterone in women may be associated with menopause or surgical removal of the ovaries, pituitary or hypothalamic dysfunction, and primary ovarian insufficiency. Factors that can lower free testosterone include aging, oral contraceptives or hormone therapies that increase SHBG, certain medications, like statins and opioids, and caloric restriction.

What’s the typical reference range for free testosterone in women?

The typical range for free testosterone in women is 0.0–4.2 pg/mL.

What’s the difference between total and free testosterone?

Total testosterone measures your body’s complete supply of testosterone (bound and unbound). Free testosterone measures only the biologically active unbound fraction of the hormone.

Do I need to fast before a free testosterone test?

You don’t typically need to fast before a free testosterone test, but always check in with your provider for special instructions.

When is the best time to test free testosterone?

Testing in the morning may yield more accurate results because testosterone levels can fluctuate throughout the day. However, if you are on testosterone replacement therapy, your desired test time may vary.

Can I test free testosterone at home?

Some at-home kits measure or calculate free testosterone, but providers may recommend confirmatory testing in a clinical lab.

Does a high level of free testosterone always mean PCOS?

Not always. While common in cases of PCOS, high free T can also occur with a number of other conditions or due to taking certain medications.

Does insurance cover free testosterone testing?

Usually, insurance will cover free testosterone testing if a provider orders it for symptoms such as infertility, hirsutism, or irregular cycles. Hers doesn’t require insurance for hormone testing.

What tests are related to this biomarker?

• Total testosterone

• Sex hormone-binding globulin

• DHEAS (dehydroepiandrosterone sulfate)

• Estradiol (E2)

• Luteinizing hormone 

• Follicle-stimulating hormone 

• Progesterone

The information provided here is for informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always talk to a qualified healthcare provider about your specific health concerns.

Related biomarkers

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Insulin-like Growth Factor 1 ( IGF-1)

Insulin-like growth factor 1 (IGF-1) reflects your body's growth hormone activity. A healthy level means your body has what it needs to support your muscle, bone, and tissue health.

Learn more about Insulin-like Growth Factor 1 ( IGF-1)

IGF-1 Z-score

Insulin-like growth factor 1 (IGF-1) reflects your body's growth hormone activity. Because IGF-1 levels vary significantly with age, sex, and pubertal stage, this Z-score is important in indicating how your IGF-1 level compares to other women in your age group, measured in standard deviations. 

Learn more about IGF-1 Z-score

Estradiol

Estradiol is a form of estrogen that men make from testosterone. At a healthy level, it supports bone strength, libido, brain function, and heart health.

Learn more about Estradiol

Follicle Stimulating Hormone (FSH)

Follicle-stimulating hormone (FSH) is a hormone produced by part of your brain called the pituitary. It is essential for sperm production and reproductive function.

Learn more about Follicle Stimulating Hormone (FSH)

Luteinizing Hormone (LH)

Luteinizing hormone (LH) is produced by part of your brain called the pituitary. It is a crucial hormone that stimulates testosterone production in the testicles.

Learn more about Luteinizing Hormone (LH)

Progesterone

Progesterone supports the menstrual cycle, preparing the uterus for pregnancy and balancing estrogen effects.

Learn more about Progesterone

Sex Hormone Binding Globulin (SHBG)

Sex hormone-binding globulin (SHBG) is a protein that carries testosterone and estrogen in the bloodstream. Unlike some other carrier proteins, it holds on to testosterone and estrogen very tightly, making them less available for your body to use.

Learn more about Sex Hormone Binding Globulin (SHBG)

Total Testosterone

Total testosterone is a measurement of all of the testosterone in your bloodstream. It counts all forms of the hormone in your blood, including free molecules and those attached to proteins like albumin and SHBG. This measurement is the go-to to determine if someone has a testosterone deficiency.

Learn more about Total Testosterone

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Reviewed by Darragh O'Carroll, MD

Published 12/04/2025