When you get your testosterone labs back, you may see multiple values and wonder what they all mean. Total testosterone is just the beginning. Understanding the complete picture requires knowing what free testosterone, SHBG, and bioavailable testosterone tell you.
Total Testosterone
Total testosterone measures all testosterone in your blood, both bound and unbound. The standard reference range is approximately 300 to 1000 ng/dL, though labs vary slightly. Many men fall in this range but still feel terrible. This is why total testosterone alone is not enough.
Free Testosterone
Free testosterone is the fraction not bound to proteins and immediately available for your cells to use. It typically represents about 1 to 4% of total testosterone. A man with total testosterone of 600 ng/dL but very high SHBG may have free testosterone in the bottom quartile of normal, explaining why he feels the symptoms of low testosterone despite an apparently normal total level.
SHBG: The Key Variable
Sex hormone binding globulin binds tightly to testosterone, making it inactive. High SHBG reduces the amount of free testosterone available. SHBG increases with age, with thyroid hormone elevation, and with certain liver conditions. It decreases with obesity, insulin resistance, and elevated androgens. Understanding your SHBG is essential to interpreting your testosterone results accurately.
Bioavailable Testosterone
Bioavailable testosterone includes both free testosterone and testosterone loosely bound to albumin, both of which are available for cellular use. This measurement gives a more complete picture than free testosterone alone.
What Optimal Looks Like
AI Matrix Health evaluates all of these values together using the Matrix Engine to identify whether your testosterone biology is truly optimal or whether intervention is warranted. This comprehensive approach is available in all 50 states via telehealth.