Why track bioavailable testosterone instead of just total?

Total testosterone includes the large SHBG-bound fraction that is unavailable to tissues. If SHBG is high, total testosterone can look normal while bioavailable testosterone is low. Tracking bioavailable testosterone — alongside SHBG — gives a truer picture of androgen status.

Why track bioavailable testosterone instead of just total?

Total testosterone includes the large SHBG-bound fraction that is unavailable to tissues. If SHBG is high, total testosterone can look normal while bioavailable testosterone is low. Tracking bioavailable testosterone — alongside SHBG — gives a truer picture of androgen status.

Home Biomarkers Hormone BalanceBioavailable Testosterone

Hormones & Vitality

Bioavailable Testosterone

The fraction of testosterone your tissues can actually use — free testosterone plus the albumin-bound portion that readily dissociates.

Optimal targetMen: 110–575 ng/dL · Women: varies

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What it measures

Bioavailable testosterone combines free testosterone (completely unbound) with the fraction loosely bound to albumin, which can release testosterone to tissues on demand. It excludes the tightly SHBG-bound portion that is effectively unavailable to cells.

Because it captures both truly free and readily releasable hormone, bioavailable testosterone is often a better reflection of androgen status than total testosterone alone — especially when SHBG is high or low.

Why it matters

Reflects the testosterone your muscles, brain, and bone can actually access.
More clinically meaningful than total testosterone when SHBG is elevated.
Helps explain low-androgen symptoms when total testosterone looks 'normal.'
Useful for monitoring testosterone therapy effectiveness over time.

What affects your levels

SHBG levels (high SHBG lowers bioavailable testosterone)

Albumin levels (albumin binds the readily releasable fraction)

Insulin resistance (lowers SHBG, raising bioavailable testosterone)

Age and thyroid function

Body composition and metabolic health

How VitalDrop tracks it

Measured alongside total testosterone and SHBG for a complete androgen picture.
Monthly trends reveal whether bioavailable hormone is stable or drifting.
Helps distinguish true androgen deficiency from binding-protein effects.

Related biomarkers

Total Testosterone Free Testosterone SHBG

Frequently asked questions

Free testosterone is the completely unbound fraction. Bioavailable testosterone includes free testosterone plus the portion loosely bound to albumin, which readily releases hormone to tissues. Bioavailable is therefore a broader, often more useful measure of the testosterone your body can actually use.

References & sources

01.

Bioavailable Testosterone: Measurement and Clinical Utility. Journal of Clinical Endocrinology & Metabolism, 2020.

02.

Sex Hormone-Binding Globulin and Testosterone Availability. Endocrine Reviews, 2019.

Medically reviewed by

Reviewed by Dr. Hassan Nasser

Medical Director — www.detroitfacemd.com

Board-certified facial plastic & reconstructive surgeon; clinical reviewer for VitalDrop laboratory insights. Verified at www.detroitfacemd.com

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Medical disclaimer: This content is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. VitalDrop provides laboratory test results and educational insights for wellness tracking. Always consult a qualified healthcare provider regarding abnormal or concerning results. Results and AI-assisted summaries are not a medical diagnosis.