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Testosterone Bioavailable

Endocrine & Reproductive

BATBioavailable testosteroneBio-TCalculated bioavailable testosterone

Review status

Currently under review

Pending specialist review and validation.

What it shows

The bioavailable testosterone test estimates the amount of testosterone in your blood that is free or loosely bound to albumin, which means it can readily enter tissues and act on cells. Most circulating testosterone is tightly bound to a protein called sex hormone binding globulin, which makes it less available to the body.

This test may be measured directly by specialized laboratory methods or calculated using total testosterone, sex hormone binding globulin, and albumin. It helps provide a clearer picture of hormone activity than total testosterone alone, especially when binding proteins are abnormal.

Why it matters

Clinicians use bioavailable testosterone to help evaluate symptoms that may relate to low androgen activity in males, such as reduced sex drive, fatigue, low mood, decreased muscle mass, and changes in body hair. It can also help assess signs of excess androgen activity in females, such as acne, unwanted hair growth, scalp hair thinning, or menstrual irregularities.

Bioavailable testosterone is especially useful when sex hormone binding globulin is altered by factors like obesity, thyroid or liver conditions, aging, or certain medicines, because total testosterone alone can be misleading in these settings. Your clinician may order this test alongside total testosterone, sex hormone binding globulin, and albumin to better understand your hormonal status and guide next steps.

Understanding your results

Your report will be interpreted using age and sex specific reference intervals from the laboratory. Higher or lower values can have many causes, and your clinician will consider your symptoms, examination, and other blood tests before making a diagnosis. If results do not match how you feel, repeating the test can be helpful, often with a morning sample collected in a consistent manner.

If levels are lower than expected in a male, your clinician may check total testosterone, sex hormone binding globulin, albumin, luteinizing hormone, follicle stimulating hormone, prolactin, thyroid tests, and liver function to look for contributing conditions. If levels are higher than expected in a female, evaluation may include tests for ovarian or adrenal causes and review of medicines. Changes in weight, thyroid status, liver health, and certain medications can shift results over time, so follow up plans are individualized.

Reference ranges

0.06 – 1.2 nmol/L
Female
0 days – 18 years
- – - nmol/L
Male
0 days – 18 years
0.06 – 1.2 nmol/L
Female
18 years – 30 years
3.6 – 11.3 nmol/L
Male
18 years – 30 years
0.06 – 1.2 nmol/L
Female
30 years – 40 years
3.6 – 11.3 nmol/L
Male
30 years – 40 years
0.06 – 1.2 nmol/L
Female
40 years – 50 years
3.6 – 11.3 nmol/L
Male
40 years – 50 years
0.06 – 1.2 nmol/L
Female
50 years – 60 years
3.6 – 11.3 nmol/L
Male
50 years – 60 years
0.06 – 1.2 nmol/L
Female
60 years – 70 years
0.8 – 6.7 nmol/L
Male
60 years – 70 years
0.06 – 1.2 nmol/L
Female
70 years – 80 years
0.8 – 6.7 nmol/L
Male
70 years – 80 years
0.06 – 1.2 nmol/L
Female
80 years – 150 years
0.8 – 6.7 nmol/L
Male
80 years – 150 years

Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.

Factors that could impact Testosterone Bioavailable

  • Time of day

    Testosterone shows a daily rhythm, usually highest in the morning. Collecting blood in the early morning and using consistent timing helps limit misleading variation.

  • Fasting and recent illness

    Fasting is not always required, but acute illness, poor sleep, and heavy exercise can temporarily lower values. Testing when you are well provides more reliable results.

  • Sex hormone binding globulin (SHBG)

    Changes in SHBG strongly affect bioavailable testosterone. SHBG can be altered by age, thyroid or liver disease, obesity, insulin resistance, and pregnancy.

  • Medications

    Androgens, anabolic steroids, estrogens, selective estrogen receptor modulators, glucocorticoids, anticonvulsants, and some HIV therapies can raise or lower levels.

  • Sample handling and method

    Different labs use different methods or calculations. Delays in processing or inconsistent methods can change results, so comparing tests from the same lab is best.

  • Special populations

    During pregnancy, with significant weight change, or with thyroid or liver conditions, SHBG shifts can make total testosterone misleading. Bioavailable testing is helpful here.

2026

References

  1. McGill University Health Centre. (2015, April 30). Testosterone Bioavailable (Task CD 699308). Laboratory reference ranges.
  2. Bhasin, S., Brito, J. P., Cunningham, G. R., Hayes, F. J., Hodis, H. N., Matsumoto, A. M., Snyder, P. J., Swerdloff, R. S., Wu, F. C. W., & Yialamas, M. A. (2018). Testosterone therapy in men with hypogonadism: An Endocrine Society clinical practice guideline. The Journal of Clinical Endocrinology & Metabolism, 103(5), 1715–1744. External link
  3. Martin, K. A., Chang, R. J., Ehrmann, D. A., Ibanez, L., Lobo, R. A., Rosenfield, R. L., Shapiro, J., & Wierman, M. E. (2018). Evaluation and treatment of hirsutism in premenopausal women: An Endocrine Society clinical practice guideline. The Journal of Clinical Endocrinology & Metabolism, 103(4), 1233–1257. External link