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Free Androgen Index (FAI)

Also referred as

Androgen Index

For men & women

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48 hours

Contains

3 tests

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The Free Androgen Index (FAI) is a blood test that measures the ratio of testosterone to sex hormone binding globulin (SHBG). It is used to assess abnormal androgen levels and diagnose hormonal disorders.

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Understanding Free Androgen Index (FAI)

The Free Androgen Index (FAI) (FAI) test helps evaluate androgen hormone levels in the body. Androgens, such as testosterone plays an important role in male and female reproductive health influencing libido, fertility, secondary sexual characteristics (hair growth, muscle mass, voice hoarseness etc.), menstrual cycles and ovarian function.

This test measures testosterone in the blood and compares the total amount of testosterone to SHBG in the body. It is recommended as a baseline investigation for suspected hyperandrogenism (androgen excess) in women. Also, it is done when there are signs and symptoms of abnormal androgen levels, which differ in men and women.

No special preparation is required for this test. Inform your doctor about all the medications or supplements that you may be taking as these may affect the test results potentially requiring adjustments or temporary discontinuation. Also, inform your doctor if you're pregnant as it can influence the testosterone levels as part of normal physiology. Moreover, narrate your complete medical history to the doctor to help them correlate your clinical and laboratory findings.

Lab Test results may vary based on the age, gender and overall health. The interpretation of test results requires professional expertise. Do not self-medicate at home and consult the doctor to understand the test results correctly.

What does Free Androgen Index (FAI) measure?

Contains 3 tests

The Free Androgen Index (FAI) test measures several key components to assess androgen status in the body. It evaluates total testosterone, which reflects the overall amount of testosterone present in the blood, including both free and bound forms. It measures Sex Hormone Binding Globulin (SHBG), a protein that binds to testosterone and regulates its bioavailability. Additionally, it also measures Free Androgen Index, a calculated ratio derived from the levels of total testosterone and SHBG, indicating the amount of free testosterone available for biological activity. The Free Androgen Index (FAI) is a useful clinical tool for evaluating androgen status in women, particularly in diagnosing conditions like polycystic ovary syndrome (PCOS) and hirsutism, by providing insight into the balance between total testosterone and sex hormone-binding globulin (SHBG). In men, the Free Androgen Index (FAI) is useful for assessing androgen levels, particularly in diagnosing conditions like hypogonadism and monitoring testosterone therapy.

Understanding these measurements is crucial for diagnosing and treating hormonal disorders, ultimately enhancing quality of life and reproductive function.

Sex Hormone Binding Globulin

The Sex Hormone Binding Globulin test measures the level of sex hormone binding globulin (SHBG) protein in the blood and is most often used to help evaluate you for testosterone deficiency or excess. SHBG is produced by the liver and it helps in the transport and regulation of sex hormones, primarily testosterone, dihydrotestosterone (DHT) and estrogen.

When the SHBG protein binds to sex hormones, your tissues can't use those hormones. Your tissues can only use sex hormones that are "free," which means they aren't attached to proteins, such as SHBG. Changes in SHBG levels can affect the amount of hormone used by the body’s tissues.

In men, SHBG binds to sex hormones like testosterone and regulates their levels in the blood. When SHBG levels are higher , less free testosterone is available for the body to use. However, when SHBG levels are lower, more free testosterone is available. This balance is important for maintaining overall health and hormonal function in men.

In women, SHBG plays an integral role in regulating the levels of bioavailable male sex hormones (androgens) and estrogens circulating throughout the body. SHBG has a higher affinity for the androgens testosterone and DHT, and so with the low SHBG, women may have signs and symptoms related to androgen excess.

Know more about Sex Hormone Binding Globulin

Testosterone Total

The Testosterone Total test measures the level of testosterone hormone available in the blood. This includes two forms of testosterone: free testosterone and bound testosterone. Bound testosterone is attached to proteins, mainly to sex hormone-binding globulin (SHBG) and albumin. It cannot enter the body's cells or directly affect tissues and organs. Instead, it acts as a store of testosterone in the blood and can be released when the body needs it. Free testosterone is not attached to any proteins and is the active form. It can easily transport to various tissues, and affects key functions like sex drive, muscle growth, bone strength, and energy levels.

Know more about Testosterone Total

Free Androgen Index

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FAQs related to Free Androgen Index (FAI)

What is the Free Androgen Index (FAI) test?

The Free Androgen Index (FAI) test is a blood test that measures levels of total testosterone, Sex Hormone Binding Globulin (SHBG) and Free Androgen Index (ratio of Total testosterone and SHBG) to assess androgen status and hormonal balance in the body.

Why would my doctor recommend the Free Androgen Index (FAI) test?

How should I prepare for the test?

Generally, no special preparation is needed for the FAI test. However, it’s advisable to discuss any medications or supplements you are taking with your doctor, as they may influence the test results.

Is fasting required before the test?

No, fasting is not required before the Free Androgen Index (FAI) test. You can schedule it at your convenience without avoiding food or water beforehand.

What do the results mean?

Results will indicate levels of total testosterone, SHBG, and the calculated FAI. Elevated or decreased levels can help diagnose conditions like polycystic ovary syndrome (PCOS) in women or hypogonadism in men.

Are there any risks associated with this test?

No, the Free Androgen Index (FAI) test is generally safe with minimal risks. However, you may feel slight discomfort during blood sample collection but chances of serious complications are extremely rare.

How often should this test be done?

The frequency of testing depends on individual circumstances and your doctor’s recommendations, especially if you are being monitored for specific hormonal conditions.

Can I have the FAI test if I’m pregnant?

Hormonal levels can fluctuate significantly during pregnancy, so it's essential to discuss the timing and necessity of the test with your doctor.

How does Tata 1mg ensure accurate lab test results?

Tata 1mg ensures accurate lab test results through certified laboratories that use advanced technology and adhere to stringent quality control measures. This commitment to high standards guarantees reliable results.

Content created by

Dr. Swati Gupta (Anand)

MD Lab Medicine, MBBS

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Last Updated

11th Oct 2025