Free Androgen Index
Private Free Androgen Index testing in London for £48, assessing one calculated androgen marker with results expected in around 1–2 days.
Turnaround time
1-2 business days
Biomarkers count
1
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Overview of the Free Androgen Index
The Free Androgen Index test reports a calculated estimate of androgen availability based on circulating Testosterone and Sex Hormone Binding Globulin.
The test assesses 1 calculated hormone marker: Free Androgen Index.
Androgens are steroid hormones that include Testosterone and related hormones.
Although Testosterone circulates in the bloodstream, much of it is bound to proteins.
Sex Hormone Binding Globulin, commonly abbreviated to SHBG, binds Testosterone relatively tightly and influences how much circulating hormone remains available to tissues.
The Free Androgen Index, or FAI, is calculated from Total Testosterone and SHBG, conventionally using the relationship between their measured concentrations.
The calculated value can provide useful information about androgen status, particularly in women.
FAI is commonly considered when investigating symptoms of androgen excess such as hirsutism, acne, scalp hair thinning or irregular menstrual cycles.
It can also provide supplementary information during investigation of polycystic ovary syndrome.
The index has important limitations.
It is not a direct measurement of free Testosterone.
Its reliability depends on the Testosterone and SHBG measurements from which it is calculated.
FAI is generally more useful in women than in men because the calculation becomes less reliable when SHBG concentrations are low and Testosterone concentrations are substantially higher.
In men, calculated Free Testosterone or other validated methods may provide more clinically useful information.
SHBG can also change because of thyroid disease, liver disease, obesity, insulin resistance, pregnancy, oestrogen exposure and some medicines.
The result should therefore be interpreted alongside Total Testosterone, SHBG, symptoms and other reproductive or androgen markers.
What Does the Free Androgen Index Test Check?
The test provides a calculated estimate of androgen availability based on Testosterone and Sex Hormone Binding Globulin. This test measures 1 calculated biomarker.
Free Androgen Index
Provides a calculated estimate of androgen availability using Testosterone and Sex Hormone Binding Globulin, supporting assessment of androgen excess or altered hormone binding in the appropriate clinical setting.
Who May Benefit From the Free Androgen Index Test ?
FAI testing is particularly useful during investigation of androgen-related symptoms in women and as part of a broader reproductive hormone assessment.
Women with excessive facial or body hair growth - Increased androgen activity can contribute to hirsutism.
Women with persistent hormonal acne - Androgen excess can increase sebaceous-gland activity in some people.
Women with irregular or absent menstrual cycles - FAI can contribute to assessment where polycystic ovary syndrome or androgen excess is being considered.
Women with scalp hair thinning and other androgenic symptoms - Hormonal evaluation may help establish whether androgen activity is relevant.
People undergoing investigation for polycystic ovary syndrome - FAI can complement Testosterone, SHBG and other reproductive hormones.
People with an abnormal Testosterone or SHBG result - The calculated index can help place these measurements into context.
People monitoring hormone treatment under clinical supervision - Repeat testing can help assess changes in androgen availability.
People undergoing a broader fertility or endocrine assessment - FAI can be considered alongside FSH, LH, Oestradiol, DHEA-S and Prolactin.
Symptoms and Reasons to Consider the Free Androgen Index Test
Changes in androgen activity can affect skin, hair and reproductive function, although symptoms are not specific to one hormonal condition.
Excess facial or body hair growth - Hirsutism can occur when androgen activity is increased.
Persistent acne - Androgens can influence skin oil production and acne development.
Scalp hair thinning - Androgen-sensitive hair follicles can contribute to patterned hair loss in susceptible individuals.
Irregular menstrual cycles - Altered androgen and ovarian hormone signalling can disrupt normal cycle patterns.
Difficulty conceiving with irregular ovulation - Androgen excess can occur alongside ovulatory dysfunction in PCOS.
Unexpectedly high or low Testosterone results - FAI can add information about the effect of SHBG on hormone availability.
An abnormal SHBG result - Changes in SHBG can materially alter calculated androgen availability.
Monitoring hormone treatment - Repeat testing may help assess treatment effects under appropriate clinical supervision.
FAI is a calculated estimate and is not a direct measurement of free Testosterone.
In men, FAI is generally less reliable than validated Free Testosterone assessment.
Symptoms of hormonal imbalance should be interpreted alongside the complete hormone profile rather than from FAI alone.
How to Prepare
Do not stop prescribed hormonal treatment solely to change the result.
FAI interpretation depends strongly on the Testosterone and SHBG values from which it is calculated.
How to Book Your Free Androgen Index Test in London
The Free Androgen Index test can be booked privately for focused assessment of calculated androgen availability.
Choose the Free Androgen Index
Select the individual Free Androgen Index test online.
Select your sample collection option
Choose an in-clinic blood draw or professional home or hotel phlebotomy where suitable.
Attend your appointment
A trained healthcare professional collects the required venous blood sample.
Laboratory analysis
Testosterone and Sex Hormone Binding Globulin measurements are used to generate the Free Androgen Index calculation according to the laboratory method.
Receive your results securely
Your authorised result is delivered securely and can be interpreted alongside Testosterone, SHBG and wider reproductive hormone markers.
When Will I Receive My Results?
The current live London Blood Tests page lists a turnaround of approximately 1–2 days after laboratory receipt for Free Androgen Index.
The laboratory completes the required hormone measurements and calculates the index before result authorisation.
Turnaround begins when the specimen reaches the laboratory rather than necessarily from the exact time of collection.
Where FAI forms part of a larger hormone panel, the complete profile may follow the turnaround of the slowest included marker.
Understanding Your Results
The Free Androgen Index provides an estimate of androgen availability derived from Testosterone and SHBG.
A higher FAI result can occur when Testosterone is raised, SHBG is reduced or both.
In women, increased FAI can provide biochemical support for androgen excess when interpreted alongside symptoms and other investigations.
This can be relevant in polycystic ovary syndrome, although FAI alone cannot diagnose PCOS.
A lower FAI result can occur with lower Testosterone, higher SHBG or both.
The significance varies substantially according to sex, age, medication and the clinical reason for testing.
SHBG is particularly important.
Oestrogen-containing contraception can increase SHBG and lower the calculated FAI.
Insulin resistance and obesity can reduce SHBG and increase FAI even without a large rise in Total Testosterone.
The laboratory reference interval should therefore be used, and interpretation should include the underlying Testosterone and SHBG results where available.
Why Book With London Blood Tests?
London Blood Tests provides private Free Androgen Index testing for focused androgen and reproductive hormone assessment.
Provides a calculated androgen marker - FAI estimates androgen availability using Testosterone and SHBG.
Useful in female androgen assessment - The calculation can support investigation of hirsutism, acne and other signs of androgen excess.
Relevant to PCOS investigation - FAI can complement other reproductive and metabolic markers where PCOS is being considered.
Accounts for hormone binding - SHBG concentration can materially change the amount of circulating Testosterone available to tissues.
Can complement Free Testosterone - Alternative calculated or measured androgen markers can provide additional information where required.
Rapid laboratory turnaround - Results are expected approximately 1–2 days after laboratory receipt.
Professional blood collection - Clinic and suitable home or hotel phlebotomy appointments are available.
Clear pricing - The Free Androgen Index test costs £48.
Private Free Androgen Index Test in London
London Blood Tests provides private Free Androgen Index testing for people requiring focused assessment of androgen availability.
The test costs £48 and reports 1 calculated hormone biomarker.
Results are expected approximately 1–2 days after laboratory receipt.
FAI is particularly useful in female androgen assessment and should be interpreted alongside Testosterone, SHBG and the wider hormone profile.