Most testosterone tests report a single total. Only a small fraction of that total — the free testosterone — is biologically active. Total testosterone with symptoms is sufficient to begin therapy; free testosterone is most useful for optimizing treatment and for resolving cases where the total does not match the clinical picture.
Reviewed by Dr. David Oliak, board-certified surgeon
Updated August 2026
Most testosterone in the blood is bound and not immediately available to tissue.
The majority is bound tightly to sex hormone–binding globulin (SHBG), and a smaller portion is bound loosely to albumin. A small fraction — roughly 1 to 3 percent of the total — is unbound, or free.
The free fraction is the biologically active testosterone: it reaches the receptors in the brain, muscle, and other tissues and produces the clinical effects. A standard total-testosterone result reports the bound and free together as one number.
A total testosterone measurement, interpreted alongside symptoms, is sufficient to diagnose low testosterone and to begin therapy. Free testosterone is not required to start.
We measure total testosterone in the office, which allows same-day assessment. For most men beginning treatment, the total result and the clinical picture together are enough to proceed.
Free testosterone becomes useful at specific points rather than as a routine initial test.
The clearest indication for free testosterone is a mismatch between the total and the symptoms.
SHBG varies between men and shifts with age, body weight, insulin resistance, thyroid function, and certain medications. When SHBG is high, more testosterone is bound and unavailable, so the free fraction can be low while the total appears adequate.
A specific example: a man with a total of 600 — solidly within the normal range — can have symptoms of low testosterone, because his free testosterone is low despite the reassuring total. Measuring free testosterone resolves that discrepancy.
Free testosterone is most valuable during treatment, for optimizing the dose.
Our general practice is to check total testosterone in the office and to assess free testosterone at 3 to 6 months after initiating therapy, then at least annually. It does not need frequent measurement.
Once a man's ratio of free to total testosterone is established, free testosterone can be calculated from a total measurement rather than measured directly each time. That makes ongoing optimization efficient without repeated specialized testing.
Interpreted alongside symptoms, free testosterone is what allows the dose to be adjusted to the biologically active hormone rather than to the total alone.
Total testosterone and symptoms are enough to make the diagnosis and start treatment; free testosterone is where optimization happens. Its value is greatest in two situations: when the symptoms do not fit the total, and when adjusting a dose during therapy.
Because free and total move together in a stable ratio for a given man, we do not need to measure free repeatedly. Once the ratio is known, a total measurement is usually sufficient to estimate it. Used this way, free testosterone refines management rather than complicating it.
— Dr. David Oliak, board-certified physician and surgeon
The objective of treatment is a man who is asymptomatic and well, not a number that clears a threshold.
The standard "normal" range describes where most men fall statistically; it is not a definition of optimized levels. Free testosterone, interpreted with symptoms, is what allows treatment to target the latter.
Combined with appropriate dosing and delivery, this is how levels are optimized rather than brought within range.
Let's begin
Total testosterone and symptoms are enough to begin; free testosterone refines the dose and resolves cases where the total does not fit how you feel. Our consult is free and includes in-office testing. To speak with us first, call 714-671-2005.
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Total testosterone measures all testosterone in the blood, most of which is bound to proteins (mainly SHBG) and unavailable to tissue. Free testosterone is the small unbound fraction — roughly 1 to 3 percent of the total — that is biologically active. The total can appear normal while the free fraction is low.
No. Total testosterone interpreted with symptoms is sufficient to diagnose low testosterone and to begin therapy. Free testosterone is not required initially; it is used when the total does not match the symptoms and for optimizing treatment.
Yes. If SHBG is high, more testosterone is bound and unavailable, so the total can appear adequate while the free fraction is low and symptoms are present. A total of 600 with clear symptoms is a typical case in which measuring free testosterone is informative.
Not frequently. Our general practice is to check total testosterone in the office and to assess free testosterone at 3 to 6 months after starting, then at least annually. Once your free-to-total ratio is known, free testosterone can be calculated from a total measurement rather than measured each time.
Not necessarily. The normal range is a statistical description of where most men fall, based on total testosterone; it is not a definition of optimized. Free testosterone, interpreted with symptoms, allows treatment to target how you function rather than only the range.
