Testosterone Total and Free

The Testosterone Total and Free test measures total testosterone and the free fraction of testosterone circulating in the blood. Testosterone is an androgen hormone present in both males and females. It contributes to reproductive and sexual function, sperm production, muscle and bone maintenance, body-hair development, red-blood-cell production and several other physiological processes.

Total testosterone represents all testosterone circulating in the bloodstream. It includes hormone bound strongly to Sex Hormone-Binding Globulin (SHBG), hormone bound more weakly to albumin and the small fraction that remains unbound. Free testosterone refers to the unbound fraction that is readily available to enter tissues.

In most people, only a small proportion of testosterone circulates freely. Changes in SHBG can alter the relationship between total and free testosterone. A person may therefore have symptoms of testosterone deficiency or excess even when total testosterone appears within the laboratory reference interval. Assessing both values can provide more information than total testosterone alone in selected patients.

Depending on the laboratory method, free testosterone may be measured directly or calculated using total testosterone, SHBG and sometimes albumin. The report should be interpreted using the method-specific reference interval. This test cannot independently diagnose hypogonadism, infertility, PCOS or another endocrine disorder.

Benefits of the Test

• Measures both total and free testosterone.
• Provides a broader assessment of circulating testosterone status.
• Supports evaluation of suspected testosterone deficiency in males.
• May help when symptoms and total testosterone results do not agree.
• Supports investigation of androgen excess in females.
• May contribute to the assessment of delayed or abnormal puberty.
• Can support evaluation of selected reproductive and sexual-function symptoms.
• May help monitor appropriately prescribed hormone-related treatment.
• Helps doctors determine whether SHBG or additional hormone tests are required.

Why Doctors Recommend This Test

A doctor may recommend total and free testosterone testing when an adult male has symptoms that could indicate testosterone deficiency. These symptoms may include reduced sexual desire, erectile difficulty, reduced spontaneous or morning erections, infertility, loss of muscle mass, reduced body hair, low bone density, hot flushes or delayed sexual development.

Total testosterone is usually the initial measurement. Free testosterone may provide additional information when the total result is borderline, when the clinical symptoms do not match the total concentration or when a condition that changes SHBG is present.

SHBG may increase with age, overactive thyroid function, estrogen exposure, pregnancy and certain liver conditions. An increased SHBG concentration may produce a normal total testosterone result while the free fraction is reduced. SHBG may decrease with obesity, insulin resistance, underactive thyroid function and androgen exposure, potentially producing a low total value while the free fraction is relatively preserved.

In females, the test may be requested when symptoms suggest androgen excess. These can include increased facial or body hair, persistent acne, scalp hair thinning, irregular or absent periods, reduced fertility or physical changes such as deepening of the voice. PCOS is a common possible cause, but ovarian, adrenal and medicine-related causes may also require consideration.

The test may be used during the evaluation of delayed puberty in boys, early puberty or atypical sexual development. Paediatric results must be interpreted according to age, sex and pubertal stage by an appropriate specialist.

Total and free testosterone testing may also be used to monitor selected patients receiving testosterone therapy, anti-androgen treatment or gender-affirming hormone treatment. The correct collection time depends on the medicine, dose, route and treatment schedule.

Preparation Before Test

A venous blood sample is collected from a vein in the arm. For adult males being evaluated for testosterone deficiency, morning collection is generally preferred because testosterone commonly reaches its highest concentration earlier in the day. Follow the specific collection time provided by the doctor or Focus Diagnostics.

Fasting requirements vary between clinical protocols. Food intake may influence testosterone, and some guidelines or laboratories prefer a fasting morning sample. Follow the instructions provided when booking, particularly if glucose, lipids or other fasting tests are ordered simultaneously.

Try to get normal sleep before testing and avoid unusually strenuous exercise immediately before the sample is collected. Inadequate sleep, acute illness, major physical stress, severe calorie restriction and recent intensive exercise may temporarily lower testosterone.

Inform the doctor about all prescribed medicines, non-prescription medicines, vitamins, protein products and supplements. Testosterone products, anabolic steroids, estrogen, hormonal contraception, glucocorticoids, opioids, anticonvulsants and several other treatments may alter testosterone concentrations.

Biotin supplements may interfere with certain laboratory immunoassays. Do not stop biotin or any prescribed medicine without instructions from the doctor or laboratory. Patients receiving testosterone treatment should provide the medicine name, dose, route and exact date and time of the last dose.

Tell the healthcare professional about liver disease, kidney disease, thyroid dysfunction, diabetes, obesity, pituitary disease, testicular or ovarian conditions, pregnancy, menopause and recent serious illness. These conditions may affect total testosterone, free testosterone or the proteins that bind testosterone.

Female patients should report pregnancy status, menstrual-cycle information and use of hormonal contraception or fertility medicines when requested. The appropriate timing depends on the clinical reason for testing.

Normal Reporting Time

The Testosterone Total and Free test is generally reported within 24 to 72 hours after the laboratory receives an acceptable serum sample. Total testosterone may be available earlier, but the complete report depends on the method used for free testosterone.

Turnaround time may be longer when testosterone is measured by mass spectrometry, free testosterone is processed using a specialised method or the sample is referred to another laboratory. Repeat analysis, dilution and quality verification may also affect reporting time.

If free testosterone is calculated, the complete result may depend on the availability of SHBG and albumin measurements. Patients requiring the report before an appointment or treatment dose should confirm the expected turnaround time with the collection centre.

Who Should Take This Test?

This test may be suitable for adult males with symptoms suggesting testosterone deficiency, particularly when a previous total testosterone result was borderline or did not correspond with the clinical findings. A doctor should determine whether both total and free testosterone are required.

Men undergoing infertility evaluation may require testosterone testing when symptoms, examination or semen-analysis findings suggest a hormonal cause. A semen analysis remains essential because testosterone testing does not directly measure sperm concentration, motility or morphology.

Females with excess facial or body hair, persistent acne, scalp hair loss, menstrual irregularity or other signs of androgen excess may be advised to undergo testing. Additional investigations may include SHBG, DHEAS, androstenedione, 17-hydroxyprogesterone, LH, FSH or pelvic imaging.

Adolescents with delayed, early or atypical pubertal development may require testosterone testing as part of specialist endocrine assessment. Adult reference intervals must not be used for children or adolescents.

Patients receiving testosterone replacement or anti-androgen therapy may require monitoring according to a clinician-defined schedule. Testing without considering the timing of the previous dose may produce misleading results.

This test should not be used for self-diagnosing low testosterone based only on nonspecific symptoms such as fatigue. Similar symptoms can occur with sleep disorders, thyroid disease, anaemia, depression, medicine effects and several other conditions.

Understanding Total and Free Testosterone

Total Testosterone: Total testosterone includes testosterone attached to SHBG, testosterone attached to albumin and free testosterone. It provides an overall measurement of circulating hormone and is commonly used as the initial test for suspected androgen deficiency or excess.

In adult males, testosterone is produced mainly by the testes under stimulation from Luteinizing Hormone (LH). In females, smaller amounts are produced by the ovaries and adrenal glands and through the conversion of other androgen hormones.

A total testosterone result may be affected by changes in binding proteins. It may therefore be misleading when SHBG is unusually high or low. An unexpected result may require SHBG, albumin and free or bioavailable testosterone assessment.

Free Testosterone: Free testosterone is the small fraction not attached to SHBG or albumin. It is available to interact with androgen receptors in tissues. The concentration is considerably lower than total testosterone and requires a sensitive analytical or calculation method.

Free testosterone may be measured using methods such as equilibrium dialysis or ultrafiltration, calculated from total testosterone and binding proteins, or assessed through other laboratory techniques. These methods are not interchangeable, and their numerical results and reference intervals may differ.

Bioavailable Testosterone: Bioavailable testosterone is related to but different from free testosterone. It generally includes free testosterone plus testosterone weakly bound to albumin. This test is specifically named Testosterone Total and Free; bioavailable testosterone should not be assumed to be included unless it appears on the laboratory report.

Sex Hormone-Binding Globulin: SHBG is produced mainly by the liver and binds testosterone strongly. SHBG is not listed as an included component of this profile. A doctor may request it separately when the total and free results are difficult to interpret or when altered binding is suspected.

Detailed Information

Testosterone production is regulated by communication between the hypothalamus, pituitary gland and testes or ovaries. The hypothalamus signals the pituitary gland, which releases LH and FSH. In males, LH stimulates testosterone production and FSH supports sperm development.

When testosterone is low, LH and FSH can help determine where the problem may originate. Low testosterone with increased LH may suggest reduced testicular response, while low testosterone with low or inappropriately normal LH may indicate pituitary, hypothalamic or systemic causes.

Testosterone concentrations change during the day and may vary from one day to another. A single low result does not necessarily establish permanent deficiency. Adult male hypogonadism is generally diagnosed only when compatible symptoms are present and low testosterone is confirmed with appropriately timed testing.

In females, increased testosterone may occur with PCOS, medicines, supplements or ovarian and adrenal disorders. Rapid development of virilising symptoms, such as voice deepening or marked new hair growth, requires prompt medical assessment.

Reference intervals vary considerably according to age, sex, pubertal stage, assay method and whether free testosterone is measured directly or calculated. Patients should use only the reference interval printed on their Focus Diagnostics report.

Results near the lower or upper limit require careful interpretation. A measured free testosterone result cannot be directly compared with a calculated result produced by another laboratory. Repeat testing should ideally use the same laboratory and analytical method when possible.

A normal result does not exclude reproductive or sexual-function disorders. Additional investigations may include LH, FSH, prolactin, SHBG, albumin, thyroid tests, estradiol, DHEAS, semen analysis, pelvic ultrasound, testicular examination or pituitary imaging.

A low testosterone result does not automatically mean testosterone therapy is required. Testosterone treatment can suppress sperm production and may be inappropriate for males currently planning fertility. Treatment decisions must consider repeated results, underlying cause, fertility plans, contraindications and potential benefits and risks.