Free testosterone blood test by The Doctors Laboratory

The TDL Free Testosterone blood test measures free testosterone in the blood and is available as an individual hormone test through The Doctors Laboratory (TDL).

Free testosterone is the fraction of testosterone that is not tightly bound to blood proteins. Measuring free testosterone can provide additional information about testosterone status alongside other hormone measurements, such as total testosterone and sex hormone-binding globulin (SHBG).

The TDL test is listed under Endocrinology and has a current laboratory turnaround time of 3 days.

At a glance

• Test: Testosterone (Free)
• TDL test code: FTES
• Sample: Blood
• Sample tube: Gold Vacutainer, SST/Gel anticoagulant, 5 mL
• Laboratory: The Doctors Laboratory (TDL)
• Turnaround: 3 days*
• Special instructions: None currently listed by TDL
• Specialty: Endocrinology

*TDL turnaround times are a guide and are measured from the point at which samples are entered into the laboratory information management system. Some tests are performed in departments that do not operate at weekends.

What is a free testosterone blood test?

Testosterone circulates in the blood in different forms. Some testosterone is bound to proteins, while a smaller proportion circulates as free testosterone.

A free testosterone blood test measures this free fraction.

Free testosterone testing may be considered alongside other hormone tests when assessing testosterone status. Depending on the individual’s circumstances, a healthcare professional may also request total testosterone, SHBG and other hormone measurements.

The appropriate combination of tests depends on the reason for testing and the individual’s clinical circumstances.

What does the TDL Free Testosterone test measure?

The TDL Testosterone (Free) test measures free testosterone from a blood sample.

The test is listed by TDL under its Endocrinology specialty with test code FTES.

Free testosterone may be considered as part of a wider assessment of androgen status. It is important to interpret the result in conjunction with relevant clinical information and, where appropriate, other hormone measurements.

Free testosterone vs total testosterone

Free testosterone and total testosterone are related but different measurements.

Total testosterone refers to the total amount of testosterone in the blood, including testosterone that is bound to proteins and the unbound fraction.

Free testosterone refers to the fraction that is not bound to proteins.

Because testosterone binding can vary between individuals, a free testosterone measurement may provide additional information when considered alongside total testosterone and SHBG.

TDL lists Testosterone (Free) and Testosterone as separate tests. The current TDL laboratory guide lists free testosterone under code FTES and total testosterone under code TEST.

Free testosterone and SHBG

Sex hormone-binding globulin (SHBG) is a protein that binds sex hormones, including testosterone.

SHBG can therefore be relevant when interpreting testosterone measurements. TDL offers SHBG as a separate blood test, and it may be requested alongside testosterone testing depending on the clinical reason for investigation.

A free testosterone result should be interpreted using the laboratory’s reference information and in the context of the individual’s other results and clinical history.

Why might someone have a free testosterone blood test?

Free testosterone testing may form part of an assessment of hormone status where testosterone levels are being investigated.

Testing may be considered in different clinical circumstances, depending on the individual’s symptoms, medical history and the reason for investigation.

Free testosterone may also be included within broader hormone testing. For example, TDL’s Erectile Dysfunction Profile includes free testosterone together with total testosterone, SHBG, free androgen index and other tests.

A standalone free testosterone test does not provide a complete assessment of hormone health and may not be the only test required.

Free testosterone testing for men and women

Testosterone is present in both men and women, although typical concentrations differ considerably.

The appropriate interpretation of a free testosterone result depends on factors such as sex, age, clinical circumstances and the laboratory’s reference intervals.

For this reason, a free testosterone result should not be interpreted using a generic online reference range.

If you are having testosterone testing because of symptoms or a specific health concern, speak to a qualified healthcare professional about which hormone tests are appropriate.

Sample requirements

For the standard venous Testosterone (Free) test, TDL currently specifies:

Gold Vacutainer
SST/Gel anticoagulant, 5 mL

TDL currently lists no special instructions for the venous Free Testosterone test.

Samples should be collected by an appropriately trained healthcare professional and handled according to the laboratory’s requirements.

Free testosterone test turnaround time

TDL currently lists a 3-day turnaround for the Testosterone (Free) test.

The quoted turnaround is a guide and is measured from the point at which the sample is entered into TDL’s laboratory information management system. Some laboratory departments do not operate at weekends.

Can free testosterone be tested by self-collection?

TDL also lists a self-collection version of Testosterone (Free), using a TDL Tiny collection tube. The self-collection test has the same FTES test code and a listed 3-day turnaround. TDL’s self-collection guidance states that samples should not be taken from an area where HRT cream has been applied.

If your testing service provides a self-collection kit, follow the collection and posting instructions supplied with that kit.

Understanding your free testosterone results

A free testosterone result should be interpreted using the laboratory’s reference range and in the context of your individual circumstances.

Testosterone levels can vary according to several factors, and a single result does not necessarily provide a complete picture of hormone status.

An abnormal result does not by itself establish a diagnosis, while a result within the reference range does not necessarily rule out every possible cause of symptoms.

If you have symptoms or concerns about your hormone levels or test results, discuss them with your GP or another appropriately qualified healthcare professional.

Frequently Asked Questions

What is a free testosterone blood test?

A free testosterone blood test measures the fraction of testosterone circulating in the blood that is not tightly bound to proteins.

What is the TDL test code for free testosterone?

The TDL test code for Testosterone (Free) is FTES.

What is the difference between free and total testosterone?

Total testosterone measures the total amount of testosterone in the blood, while free testosterone measures the unbound fraction.

They provide different information and may be considered together when assessing testosterone status.

Does free testosterone measure the same thing as total testosterone?

No. Free testosterone and total testosterone are different measurements. TDL lists them as separate tests: FTES for Testosterone (Free) and TEST for Testosterone.

Should I test free testosterone or total testosterone?

The appropriate test depends on why you are having testosterone testing and your individual circumstances.

In some situations, a healthcare professional may request both total testosterone and free testosterone, potentially alongside SHBG and other hormone tests.

Should I test SHBG with free testosterone?

SHBG may be useful when assessing testosterone status because it is one of the proteins that binds testosterone in the blood.

Whether SHBG should be tested alongside free testosterone depends on the clinical circumstances and the reason for testing.

Does the free testosterone test include SHBG?

No. SHBG is a separate TDL test.

If SHBG is required, it needs to be included as an additional test or ordered as part of a profile that contains SHBG.

What sample is required for the TDL Free Testosterone test?

TDL specifies a Gold Vacutainer with SST/Gel anticoagulant, 5 mL for the standard venous Testosterone (Free) test.

Do I need to fast before a free testosterone test?

TDL’s current listing for the standard Testosterone (Free) test states no special instructions.

If your healthcare provider gives you specific preparation instructions, follow those instructions.

How long do free testosterone results take?

TDL currently lists a 3-day turnaround for Testosterone (Free).

The turnaround is a guide and applies from the point at which the sample is entered into TDL’s laboratory information management system.

Can women have a free testosterone test?

Yes. Testosterone is present in women as well as men, although concentrations and reference intervals differ.

The appropriate interpretation depends on the individual’s circumstances and the laboratory’s applicable reference range.

Can free testosterone diagnose low testosterone?

A free testosterone result should not be used on its own to establish a diagnosis.

Test results need to be interpreted alongside symptoms, medical history, other hormone measurements and the laboratory’s reference information.

What can cause a low or high free testosterone result?

Testosterone levels can vary for a number of reasons, including biological variation, medication, health conditions and differences in hormone-binding proteins.

A result outside the laboratory reference range therefore requires appropriate clinical interpretation rather than being considered diagnostic on its own.

Is free testosterone the same as bioavailable testosterone?

No. Free testosterone and bioavailable testosterone are related but distinct measurements.

TDL lists Testosterone (Free) as FTES. A separate bioavailable testosterone test has historically been listed by TDL under code BTES, so the two should not be treated as interchangeable.

Is the TDL Free Testosterone test available as a self-collection test?

Yes. TDL currently lists a self-collection version using its TDL Tiny collection system. The self-collection version is also coded FTES and has a listed 3-day turnaround.

Can I take a free testosterone test while using HRT?

If you are using hormone replacement therapy, tell the healthcare provider arranging your test.

For TDL’s self-collection version specifically, TDL advises avoiding collection from an area where HRT cream is applied.

Important Information and Disclaimer

The TDL Free Testosterone blood test measures free testosterone in a blood sample. It is a laboratory test and is not a substitute for a medical consultation, physical examination or clinical assessment.

Testosterone results should be interpreted using the reference ranges provided by the testing laboratory and in the context of your individual circumstances, including age, sex, symptoms, medical history, medication and any other relevant test results.

A result outside the laboratory reference range does not necessarily indicate a medical condition, while a result within the reference range does not necessarily exclude one.

Free testosterone testing alone does not establish a diagnosis or determine whether testosterone treatment is appropriate.

If you have symptoms, are taking hormone replacement therapy or testosterone, or have concerns about your hormone levels or results, speak to your GP or another appropriately qualified healthcare professional.

Laboratory: The Doctors Laboratory (TDL)
Test: Testosterone (Free)
TDL test code: FTES
Standard sample: Gold Vacutainer, SST/Gel anticoagulant, 5 mL
Listed turnaround: 3 days
Special instructions: None currently listed for the standard venous test

Laboratory specifications, sample requirements and turnaround times can change. The current TDL laboratory requirements should be followed when arranging and collecting samples.