Total testosterone of 600 ng/dL without SHBG: what the science says

What did @mytrt.health actually say?

The creator's transcript is, frankly, incoherent. The words captured on record are a string of fragmented sentences about testing a device, taking something "back and forth," and a reference to "Blint Fluke" and a "red flag." None of this constitutes a medical claim you can evaluate directly.

The caption, however, tells a clearer story. The claim there is that a total testosterone reading of 600 ng/dL is meaningless, or worse, misleading, without a corresponding SHBG (sex hormone-binding globulin) value. The caption calls this a "Blindflug" (blind flight) and labels the lone total testosterone result a "red flag." That is the claim we are fact-checking here, because the audio did not deliver it.

Worth noting: when a creator's transcript does not match their caption, that is a credibility problem in itself. Viewers watching on mute are getting one message; viewers listening are getting word salad.

Does the science back this up?

The underlying biology here is solid, even if the delivery was not. Total testosterone measures both bound and unbound testosterone in circulation. Most of it, roughly 60 to 80 percent, is tightly bound to SHBG and is considered biologically inactive. Another portion binds loosely to albumin. Only the free fraction, typically 1 to 3 percent of total, readily enters cells and drives androgen action.

This is not fringe science. Rosner et al. (2007, Journal of Clinical Endocrinology and Metabolism) documented that total testosterone alone is insufficient for diagnosing androgen deficiency in men with altered SHBG concentrations. Men with high SHBG, common in older men, liver disease, or hyperthyroidism, can have a total testosterone of 600 ng/dL while their free testosterone sits well below the reference range. Conversely, men with low SHBG, seen in obesity and type 2 diabetes, may have a lower total testosterone but adequate free hormone. The Endocrine Society's 2018 clinical practice guideline on male hypogonadism explicitly recommends measuring free or bioavailable testosterone when total testosterone results are borderline or when SHBG abnormalities are suspected.

What did they get wrong (or right)?

The caption's core argument is correct. Clinicians who stop at total testosterone without considering SHBG are working with incomplete data, particularly in patients who are symptomatic despite "normal" labs. Credit where it is due: this is a real diagnostic gap that affects real patients.

What they got wrong, or at least oversimplified, is the framing of 600 ng/dL as a "red flag" on its own. It is not a red flag. It is an incomplete picture. Those are different things. A red flag implies something is wrong. An incomplete picture means you need more information. Conflating the two creates unnecessary anxiety in viewers who may have a 600 ng/dL result sitting in their patient portal right now.

There is also no acknowledgment that free testosterone measurement has its own limitations. Direct free testosterone immunoassays, the kind most commercial labs run, are notoriously inaccurate. Vermeulen et al. (1999, Journal of Clinical Endocrinology and Metabolism) showed that calculated free testosterone using total testosterone, SHBG, and albumin is more reliable than direct assay in most clinical settings. Ordering SHBG alone does not fully solve the problem.

What should you actually know?

If you are getting testosterone labs done and your clinician only ordered total testosterone, asking about SHBG is a reasonable and informed request. It is not demanding. It is standard practice in any thorough hormone evaluation.

The calculation matters too. Free testosterone can be estimated using the Vermeulen formula or the SHBG-based calculation endorsed by the Endocrine Society. Neither requires a direct free testosterone assay, which, again, is often inaccurate. Many telehealth platforms and endocrinologists use this calculated value alongside total testosterone and SHBG to build a more complete picture.

Context also shapes interpretation. Age, BMI, comorbidities like type 2 diabetes or liver disease, and medications such as certain anticonvulsants or thyroid hormones all shift SHBG. A 35-year-old lean man with 600 ng/dL and normal SHBG is in a very different position than a 55-year-old with the same total testosterone and elevated SHBG. A number without context is not automatically a crisis, but it is genuinely incomplete.

• Do not make treatment decisions, including starting TRT, based on total testosterone alone.
• SHBG, albumin, and total testosterone together allow a calculated free testosterone that is more clinically useful than the direct assay at most labs.
• Symptoms matter as much as labs. Biochemical hypogonadism without symptoms is not an automatic indication for therapy.