Free androgen index blood test in Chiswick

What the test measures

Most testosterone in the blood is bound to proteins. Sex hormone binding globulin (SHBG) holds it tightly, while albumin holds it loosely. Only the small free portion, and the loosely bound part, can act on tissues. The free androgen index (FAI) is calculated from total testosterone and SHBG, giving an estimate of how much testosterone is active.

FAI is used mostly in women, where it helps to assess signs of higher androgen levels, such as excess hair growth, acne or irregular periods, and is part of the assessment for polycystic ovary syndrome. In men, total testosterone with SHBG, or a calculated free testosterone, is usually more reliable, but FAI can still add context.

Your price includes the sample taken at our Chiswick clinic, analysis at the Randox accredited laboratory, a practitioner review of your result and a GP feedback report on request.

Who it is for

• You have irregular periods, acne or unwanted hair growth and want androgen levels checked.
• You are being assessed for polycystic ovary syndrome.
• You have low libido, low energy or low mood and want to understand your testosterone.
• You have a condition or take a medicine that can change SHBG, such as thyroid disorders or oral contraception.
• You want to follow up an earlier testosterone result.

Understanding your result

Your report shows testosterone, SHBG, albumin and the free androgen index against the laboratory reference range for your sex. In women, a raised FAI often goes with a high testosterone or a low SHBG, which can be seen with PCOS, insulin resistance or weight gain. A low FAI in men may go with low testosterone or a high SHBG.

SHBG is affected by thyroid function, liver health, weight, age and hormonal contraception, so your practitioner reads the full picture. A result outside the range is a prompt for discussion, not a diagnosis of PCOS or any other condition.

Preparing for your test

Book a morning appointment, ideally before 10am, because testosterone is highest in the morning. Fasting is not essential but can help, as a large meal can lower testosterone a little. Women with a regular cycle are often tested in the early part of the cycle, and we will confirm timing when you book. Tell us about any hormonal contraception, HRT or testosterone treatment, and pause biotin for two days where safe.

For men, our testosterone tests offer more detail. For women, the Fertility Panel with AMH includes FAI with other hormones. There is also a list of every blood test and price in Chiswick.

Questions

How much is a free androgen index test in Chiswick?

The Free Androgen Index test costs £69. This includes your blood sample at our Chiswick clinic, analysis at the Randox accredited laboratory, a practitioner review and a GP feedback report on request.

Can this test diagnose PCOS?

No single blood test diagnoses PCOS. The diagnosis is based on a combination of symptoms, blood tests and sometimes an ultrasound scan, and your GP can guide this.

Why is SHBG important?

SHBG binds testosterone and makes it inactive. A high SHBG can mean less testosterone is available even when total testosterone looks normal.

What time of day should I test?

A morning appointment, ideally before 10am, gives the most reliable reading.