Free and Bioavailable Testosterone Calculator
Estimate your active free and bioavailable testosterone using your Total Testosterone, SHBG, and Albumin blood test results.
Understanding Free and Bioavailable Testosterone
Use this tool to estimate your free and bioavailable testosterone from your total testosterone, SHBG, and albumin blood test results. This can help provide a clearer picture of the testosterone available to your body, particularly when total testosterone alone does not tell the full story.
These calculated parameters more accurately reflect the level of bioactive testosterone than the measurement of total serum testosterone alone. Testosterone and dihydrotestosterone (DHT) circulate in plasma either unbound (free; approximately 2–3%), bound to specific plasma proteins such as sex hormone-binding globulin (SHBG), or weakly bound to non-specific proteins such as albumin.
Vermeulen Formula Calculator
Enter your blood test values and select your preferred units below.
Disclaimer: Results from this calculator should NOT be solely relied upon in making (or refraining from making) any decision in any case/circumstances without prior consultation with medical professionals. No responsibility whatsoever is assumed for its correctness or suitability for any given purpose.
WARNING! The calculated free and bioavailable testosterone are reliable in most clinical situations, but should not be relied upon in situations with potential massive interference by steroids binding to SHBG (e.g., during pregnancy in women, or in men receiving treatments that induce high levels of DHT or mesterolone).
What do these results mean?
Total Testosterone
The total amount of testosterone measured in your bloodstream, representing both bound and unbound hormones.
Free Testosterone
The small proportion (typically 1–2%) of testosterone not attached to proteins and immediately available for your body to use.
Bioavailable Testosterone
The testosterone readily available to your body, comprising free testosterone plus testosterone loosely attached to albumin.
SHBG (Sex Hormone Binding Globulin)
A protein that binds strongly to testosterone. Higher SHBG levels can reduce the amount of testosterone available for your body to use, even when total testosterone appears normal.
Albumin
A common transport protein in your blood. Testosterone attached to albumin is weakly bound and can still be readily released and used by your tissues.
Why symptoms matter
Testosterone levels are only one part of the picture. Some men with testosterone levels outside the normal range experience very few symptoms, while others experience severe, debilitating symptoms despite test results that appear "normal".
Reduced body and facial hair
Loss of muscle mass
Flabby pectoral muscles (gynecomastia)
Low libido, erectile dysfunction, and changes in testicular size
Hot flushes and night sweats
Irritability, poor concentration, and low mood
Disturbed sleep patterns and chronic fatigue
Weight gain and increased visceral body fat
Brittle bones and an increased risk of fracture
Reduced sperm count and fertility concerns
Understanding your result
Your calculated free and bioavailable testosterone levels may provide additional information alongside your total testosterone result. Results should always be interpreted together with:
- ✓Your presenting clinical symptoms
- ✓Full medical and personal health history
- ✓Current medications and supplements
- ✓Other hormone panels and full blood count results
Why a clinician review is important
Testosterone results can be influenced by a range of factors, including age, weight, sleep, stress, medications, medical conditions, and the time of day your blood sample was taken.
A clinician can review your results alongside your symptoms and broader health profile to help determine the most appropriate next steps.
Discuss your results with a clinician
Our medical team can review your blood test results and symptoms to help you better understand what they mean. Book a consultation or call with our specialists today.