The Free Androgen Index (FAI) blood test is a calculation that measures the balance between total testosterone and sex hormone-binding globulin (SHBG) in the blood. It provides an estimate of how much free, active testosterone is available for the body to use.

This test is particularly important in assessing conditions related to hormone imbalance, including polycystic ovary syndrome (PCOS) in women, low testosterone in men, and metabolic or reproductive health concerns. By understanding your FAI levels, doctors can gain insights into hormonal health, energy levels, fertility, and overall wellbeing.

This guide explains what it is, how it works, what your results mean, and how you can book a comprehensive blood test to check your Free Androgen Index (FAI).

What is Free Androgen Index (FAI)?

The Free Androgen Index (FAI) is a calculation that shows how much active testosterone is available in your body. Testosterone in the blood exists in two forms: bound (attached to proteins like SHBG) and free (ready for the body to use). FAI compares total testosterone with SHBG to estimate the amount of free testosterone.

A simple way to picture this is like money in your bank account. Most of it might be “locked” in a savings account (bound testosterone), while only a smaller portion is “spending money” you can use right away (free testosterone). The FAI tells you how much of that usable energy you really have.

Quick facts:

• FAI = (Total Testosterone ÷ SHBG) × 100
• Low FAI may mean reduced energy, muscle strength, or libido.
• High FAI can point to conditions like PCOS in women or excess androgens.

Knowing your FAI helps assess hormone balance, metabolic health, and overall wellbeing. It’s often tested when symptoms like fatigue, irregular periods, fertility issues, or changes in weight or mood appear.

Why is Free Androgen Index (FAI) important?

The Free Androgen Index (FAI) offers a window into your hormonal balance, metabolic health, and long-term vitality. Since free testosterone is the “active” form that influences tissues (while most testosterone is bound and inactive), FAI helps estimate how much of your androgen is actually usable. In doing so, it links directly to energy levels, body composition, insulin sensitivity, and even aging.

When FAI is too low, it can contribute to fatigue, loss of muscle, poor libido, and increased risk of weight gain or osteoporosis. In men, androgen decline is associated with rising age, obesity, and chronic disease; SHBG tends to rise ~1–2% per year, compounding the drop in free testosterone.

Conversely, high FAI (i.e. excess free androgen) is a hallmark in conditions like PCOS, driving metabolic issues, irregular cycles, acne and weight gain. In women with PCOS, FAI is strongly associated with hirsutism and poorer quality of life.

Globally, endocrine studies show that alterations in androgen balance correlate with insulin resistance and oxidative stress. Because FAI reflects how well your body is handling hormones, it can serve as an early red flag, allowing intervention before overt metabolic disease or hormonal damage sets in.

Empowered with this insight, you can adjust lifestyle, nutrition or seek medical assessment — long before symptoms escalate.

When should you get a Free Androgen Index (FAI) test?

You may be advised to check your Free Androgen Index (FAI) if you have symptoms or risk factors that suggest a hormone imbalance. Testing can help uncover hidden issues before they affect long-term health. Common scenarios include:

• Ongoing fatigue, low energy, or reduced muscle strength
• Irregular or absent menstrual cycles, or suspected polycystic ovary syndrome (PCOS) in women
• Low libido, erectile dysfunction, or concerns about fertility in men
• Unexplained weight gain, insulin resistance, or metabolic syndrome
• Family history of hormonal disorders, PCOS, or early menopause/andropause
• Monitoring hormone-related changes during pregnancy
• Referral from a GP or specialist when other hormone markers, such as SHBG or total testosterone, are outside the normal range

Checking your FAI can provide valuable context for your overall metabolic and reproductive health, helping guide the right next steps.

How does the Free Androgen Index (FAI) test work in Australia?

The FAI test is not a single “stand-alone” procedure—it’s derived from measuring total testosterone and sex hormone-binding globulin (SHBG) in your blood, then applying a formula. In Australia, here’s how it typically works:

Preparation

You usually don’t need to fast for testosterone or SHBG tests, unless your doctor also orders tests like fasting glucose or lipid panels. Blood is drawn in the morning when hormone levels are more stable. Pathology providers recommend taking the sample between about 7 am and 10 am where possible.

Medicare coverage & test cost

• Medicare may partially rebate hormone and binding protein tests under MBS Item 66695, which covers quantitation of hormones and hormone binding proteins (including SHBG and testosterone).
• The MBS schedule fee for Item 66695 is A$30.50; Medicare pays 75% for non-concessional patients or 85% for concessional/special cases.
• However, not all providers bulk-bill or accept the full Medicare rebate; you may face out-of-pocket costs depending on the lab’s pricing policy.
• Private pathology services (especially direct-to-consumer testing) often charge full fees, and such tests may not be Medicare-rebated. For example, some providers clearly state their hormone tests are privately billed and not eligible for Medicare coverage.

Access via comprehensive panels

You can access the FAI calculation as part of broader hormone or metabolic panels (e.g. including testosterone, SHBG, oestradiol, LH/FSH). Your GP or endocrinologist can request such a panel via a referral, often ensuring eligibility for Medicare rebates. Many private labs also package these into “hormone health” or “men’s/women’s wellness” panels, but those may not always be subsidised.

If you’re ordering privately or through an online pathology service, check whether Medicare rebates apply, whether the lab bulk-bills, and whether you’ll pay a gap amount.

What do my Free Androgen Index (FAI) results mean?

Your Free Androgen Index (FAI) results give insight into how much free, active testosterone is available in your body compared with the amount bound to SHBG. A healthy balance supports energy, muscle strength, reproductive health, and metabolism. When results fall outside the reference range, it may signal an underlying issue that needs further review.

Here’s a simple guide to interpreting your FAI results:

It’s important to remember that FAI is just one piece of the puzzle. Doctors often look at other hormone markers such as total testosterone, SHBG, and oestradiol to build a clearer picture of your health. Related tests like Sex Hormone-Binding Globulin (SHBG), Testosterone, and Oestradiol can help provide more context to your results.

Always discuss your results with your GP or specialist, as interpretation depends on your age, sex, symptoms, and overall health.

Free Androgen Index (FAI) in context with other tests

The Free Androgen Index (FAI) is a valuable tool for estimating active testosterone, but it works best when interpreted alongside other hormone markers. Looking at FAI alone can sometimes be misleading, as changes in SHBG or total testosterone may affect the calculation. To get a clear picture of hormonal health, doctors usually review FAI together with related tests.

Key markers often assessed with FAI include:

• Total Testosterone: Shows overall testosterone levels, helping confirm if low or high FAI is due to changes in testosterone itself
• Sex Hormone-Binding Globulin (SHBG): Essential for calculating FAI; high SHBG lowers free testosterone, while low SHBG raises it
• Oestradiol (E2): Important for women’s reproductive health and balance between male and female hormones
• Luteinising Hormone (LH) and Follicle-Stimulating Hormone (FSH): Provide clues about whether hormone imbalance originates in the ovaries/testes or the pituitary gland

By combining these results, doctors can better understand the root cause of symptoms such as fatigue, irregular cycles, infertility, or metabolic changes. This holistic approach ensures FAI is seen as part of a bigger picture, not in isolation.

Lifestyle and practical steps for Free Androgen Index (FAI)

Your Free Androgen Index (FAI) reflects the balance between active testosterone and SHBG, and lifestyle choices play a big role in keeping this balance healthy. While medical treatment may be needed in some cases, simple daily habits can support better hormone function and overall wellbeing.

1. Diet: Focus on whole foods, lean protein, healthy fats, and fibre. Limiting processed foods and added sugars can improve insulin sensitivity and help maintain balanced FAI levels.
2. Exercise: Regular activity, especially strength training and moderate cardio, supports testosterone production and helps reduce excess body fat, which can otherwise raise SHBG and lower FAI.
3. Sleep: Getting 7–9 hours of quality rest is crucial, as poor sleep reduces testosterone and disrupts hormone regulation.
4. Stress management: Chronic stress raises cortisol, which competes with testosterone. Simple practices such as mindfulness, yoga, or daily walking can lower stress and protect hormone balance.
5. Limit alcohol and smoking: Both negatively affect hormone production. Reducing or avoiding them helps maintain healthier testosterone and better metabolic health.

The best starting point is testing — once you know your levels, you can take personalised steps.

FAQs about the Free Androgen Index (FAI) test in Australia

What is the Free Androgen Index (FAI) blood test?

The FAI test is a calculation that compares total testosterone and sex hormone-binding globulin (SHBG). It estimates how much free, active testosterone is available in the body.

How much does a Free Androgen Index (FAI) test cost in Australia?

If ordered by a GP for clinical reasons, Medicare may cover part or all of the cost. Private testing without a referral usually ranges from $40 to $80, depending on the provider.

Is the Free Androgen Index (FAI) test covered by Medicare?

Yes, Medicare provides a rebate when the test is medically necessary, such as for suspected PCOS, low testosterone, or fertility issues. Out-of-pocket costs may still apply if the lab does not bulk-bill.

Do I need a referral for an FAI test?

In most cases, yes. A GP or specialist referral is required for Medicare rebates. Some private labs offer self-request testing, but this is not usually covered by Medicare.

Can pregnant women have an FAI test?

Yes, but results must be interpreted carefully, as hormone levels naturally change during pregnancy. Doctors often use FAI alongside other markers to get an accurate picture.

What symptoms suggest I may need an FAI test?

Common symptoms include fatigue, low libido, infertility, irregular periods, acne, or unexplained weight changes. Your doctor may also recommend it if other hormone markers are abnormal.

What is the normal range for FAI?

In adults, the typical reference range is about 14.5–80.3%. Results outside this range may suggest hormone imbalance and should be discussed with a healthcare professional.

Conclusion

The Free Androgen Index (FAI) is a key measure of how much free, active testosterone is available in your body. By comparing total testosterone with SHBG, it provides valuable insight into your hormone balance, energy, fertility, and metabolic health. Whether you are experiencing symptoms like fatigue, irregular periods, low libido, or changes in weight, testing your FAI can help uncover the underlying cause and guide the right next steps.

Understanding your FAI results doesn’t just highlight potential risks — it gives you the knowledge to make informed choices about your lifestyle and healthcare. With the right information, you can work with your doctor to address imbalances before they lead to more serious conditions.

Take control of your health today. Sign up for our comprehensive blood test and get clear insights into your Free Androgen Index (FAI) and more than 50 other key markers.

References

• RACGP – Assessment and management of male androgen disorders
• MBS Item 66695
• Systematic review: Androgen measures including FAI in PCOS diagnosis
• SHBG – Pathology Tests Explained
• “The Effect of Free Androgen Index on the Quality of Life of Women With PCOS”