A 54-year-old man slides a lab printout across the desk and says, "My doctor told me my testosterone is fine. Total T is 562. But I feel terrible. What am I missing?" What he is missing is the rest of the panel. His total T is 562 ng/dL, which lands him squarely inside the standard reference range. His SHBG, which his primary care physician did not order, is 78 nmol/L — well above the upper limit of normal. When I run a calculated free testosterone using the Vermeulen equation, his free T comes out at 5.8 ng/dL, against a functional threshold of around 9 to 10 ng/dL for a man his age. Biologically, he is testosterone-deficient. Clinically, he has been told for two years that he is fine. The lab number lied — or more accurately, the lab number was incomplete, and the clinician reading it did not catch what was missing.
This is one of the most common scenarios I see in middle-aged patients across Columbus and Warner Robins, and it is the entire reason this article exists. Total testosterone is a useful number. By itself, it is not a diagnostic conclusion. Understanding the difference between total and free testosterone — and the protein that determines that difference — is the difference between getting an honest answer about your physiology and getting brushed off.
What total testosterone actually measures
When a lab reports total testosterone, what is being measured is every molecule of testosterone in the bloodstream regardless of what is doing — whether it is bound to a protein and inactive, or floating free and ready to bind a receptor. The total pool includes three fractions:
SHBG-bound testosterone — about 60 to 70 percent of total testosterone in a typical adult male. This fraction is bound tightly to sex hormone-binding globulin and is biologically inactive. It cannot enter cells. It cannot bind androgen receptors. It is, for the purposes of the symptoms you feel, invisible.
Albumin-bound testosterone — about 30 to 40 percent. Loosely bound, can release at the tissue level under the right conditions, considered "bioavailable" in some clinical frameworks.
Free testosterone — only about 1 to 3 percent of total. Completely unbound. The fraction that actually enters cells, binds androgen receptors, and produces every effect testosterone is supposed to produce.
When a primary care physician orders only total T, they are getting the sum of all three. That number tells you nothing about how the testosterone is distributed across those fractions — and the distribution is what drives the symptoms.
How SHBG quietly drives the whole picture
SHBG is the variable most missed in conventional testing, and it is the variable that most often explains why a "normal" total testosterone is not actually normal for the patient sitting in front of me.
SHBG goes up with age in both men and women. It goes up with hyperthyroidism. It goes up with liver disease. It goes up with chronic inflammation. It goes up with very low-calorie dieting. It goes up with certain medications, including anticonvulsants, oral estrogens, and some HIV medications. And when it goes up, it binds more testosterone, which means less testosterone is free, which means the patient feels deficient even when total T looks fine.
The reverse is also true. SHBG goes down with insulin resistance. It goes down with obesity. It goes down with hypothyroidism. It goes down with certain steroid exposures. When SHBG is low, free testosterone can look surprisingly preserved even in the face of a relatively low total T — sometimes that buys a man a few years of feeling reasonable while his total T quietly slides.
The clinical implication: if a clinician is making decisions based on total T alone, they are making decisions on incomplete information about half the patients they see. I have lost count of how many men have come into the clinic with "normal" total T results and clearly low free T because nobody pulled SHBG into the equation.
The mechanism that determines what you actually feel
Testosterone produces its biological effects by entering cells and binding to intracellular androgen receptors. The bound receptor then translocates into the nucleus, binds DNA at androgen response elements, and changes gene expression. That cascade is what produces the muscle protein synthesis, the libido signaling, the erythropoietic effect, the bone mineral density support, the mood and motivation effects, and every other downstream consequence of having adequate testosterone.
Only free testosterone can do this. SHBG-bound testosterone cannot enter the cell. It is a circulating reservoir, not an active hormone. When you measure free T, you are measuring the fraction that is doing the actual work.
This is why two patients with identical total testosterone numbers can have completely different symptoms. A man with total T of 500 and SHBG of 25 has free T around 11 to 12 ng/dL — adequate. A man with total T of 500 and SHBG of 75 has free T around 6 ng/dL — functionally deficient. Same total T. Same lab printout. Two completely different physiologies. The total T number does not distinguish them. The free T calculation, derived from total T, SHBG, and albumin using the Vermeulen equation, does.
Why I prefer calculated free T to direct free T assays
Free testosterone can be measured two ways. Some labs run a direct immunoassay or analog assay for free T. Others report a calculated free T derived from total testosterone and SHBG.
The direct assays have well-documented accuracy problems, especially at the lower end of the curve where the answer matters most. The numbers you measure that small are technically difficult to pull cleanly out of serum, and the results can vary widely between labs and even between runs at the same lab. Endocrinology guidelines have recognized this for years.
The calculated free T using the Vermeulen equation — which uses total testosterone, SHBG, and albumin to estimate free T based on validated binding constants — correlates much more reliably with equilibrium dialysis (the gold-standard reference method) across the physiological range. It is the calculation I use in clinic, and it is what I want from any lab I order.
Not sure where to start?
The Start Here pathway walks you through the most common entry points and helps you decide which consultation type is the right fit. Five minutes of self-assessment can save you a wrong-direction conversation.
Equilibrium dialysis itself is the most accurate measurement, but it is expensive, slow, and not necessary for routine clinical decision-making. Calculated free T from a properly drawn total T and SHBG is the workhorse of comprehensive lab work in my practice.
What I look for when I read your panel
When a lab printout comes across my desk for a man who is being evaluated for possible androgen deficiency, here is the order I work through it:
First, total testosterone. I want it drawn fasting, between 7 and 10 AM, on at least two separate occasions before I consider the value confirmed. A single afternoon draw is not adequate evidence of anything.
Second, SHBG. This tells me whether the total T number is being distorted by binding-protein behavior in either direction.
Third, calculated free T. This is the number that actually correlates with how the patient feels.
Fourth, sensitive estradiol — measured by LC-MS/MS, not standard immunoassay. The standard assay is not accurate at the low estradiol concentrations seen in men, and using the wrong assay leads to either ignored estradiol problems or, equally bad, unnecessary aromatase inhibitor use.
Fifth, LH and FSH. These tell me whether the issue is primary (testicular failure, with high LH and FSH) or secondary (HPG axis suppression, with low or inappropriately normal LH and FSH).
Sixth, prolactin. A prolactin above 25 in a man with low T gets a pituitary MRI before I consider anything else.
Seventh, DHEA-S, full thyroid panel, fasting insulin and HbA1c, lipid panel, hs-CRP, and a CBC. These markers establish the metabolic and adrenal context that affects both interpretation and treatment planning.
PSA and a baseline hematocrit before any men's testosterone replacement is initiated, every time. My years in the cath lab made me cautious about anything that elevates hematocrit and red cell mass, and I will not start a protocol without those baselines.
How this changes the treatment conversation
Once the panel is complete, the treatment conversation becomes specific rather than generic. A man with low total T, low free T, low LH and FSH, and elevated prolactin is not a TRT candidate — he is an MRI candidate. A man with normal total T, high SHBG, low free T, and clear symptoms might benefit from interventions that lower SHBG (resistance training, addressing the underlying driver — thyroid, liver, medication) before any exogenous testosterone is considered. A man with low total T, low free T, normal LH and FSH, and elevated estradiol might need both testosterone and an estradiol management strategy from the start.
Treatment decisions made on total T alone treat half the picture. Treatment decisions made on the full panel treat the patient.
When hormone optimization or men's testosterone replacement is the right answer, the protocol is conservative. I start low, monitor closely, and titrate based on labs at six to eight weeks and again at twelve weeks. The goal is steady, physiologic levels — total T in the upper-normal range for age, free T at the upper end of the functional range, estradiol controlled, hematocrit safe. Not supraphysiologic. Not "more is better." Optimization is calibration, not maximization.
For patients who prefer not to inject, Biote pellet therapy is a reasonable alternative that delivers steady levels for three to five months per insertion.
The concrete next step
If you have been told your testosterone is "normal" but you do not feel normal, the most useful thing you can do is get a complete panel and have someone read it with you who understands the difference between total and free T.
Get a fasting morning lab draw — between 7 and 10 AM, on two separate occasions about two weeks apart — that includes total testosterone, SHBG, calculated free testosterone, sensitive estradiol (LC-MS/MS), LH, FSH, prolactin, full thyroid (TSH, free T3, free T4, reverse T3, antibodies), DHEA-S, fasting insulin and HbA1c, lipid panel, hs-CRP, CBC, and PSA if you are over 40.
Bring the results. Book a consultation at the Columbus location or the Warner Robins location. If you do not have recent labs, we can order the panel at your first visit. Use the hormone health assessment if you want to think through your symptom picture before booking.
The conversation worth having is the one grounded in the full lab picture — not the abbreviated version. That is how you find out whether your testosterone is actually fine, or whether it is fine on paper and deficient in your body.
Medical disclaimer: This article is for educational purposes only and does not constitute medical advice. Individual clinical decisions should be made in consultation with a qualified healthcare provider following appropriate evaluation. References to specific treatments, dosing, or protocols are informational.
Travis spent 17+ years in high-acuity clinical medicine — emergency, cardiac ICU, and cath lab — before founding Revitalize. He is a Certified Platinum Biote hormone therapy provider, the published author of You're Not Broken — You're Unbalanced, and the founder of the Rebuild Metabolic Health Institute. His clinical writing reflects the same precision he brought to critical care: specific, honest, and built around what actually works.
Ready to talk it through with a clinician?
Book online or call either Georgia location. Every visit starts with a consultation.