The headline: two cutoffs, one shared rule
The American Urological Association (AUA) and the Endocrine Society disagree on where to draw the line for low testosterone by about 36 ng/dL, and agree on almost everything else. Both say a diagnosis needs low numbers on repeat early-morning testing and symptoms or signs that fit. Neither says a single low result, or symptoms alone, are enough.
The differences show up at the edges: which number counts as low, how much weight free testosterone gets, what level to aim for on treatment and how often to recheck. For a man whose result sits in the gray zone, those edges are the whole question.
Side by side
| AUA (2018, validity confirmed 2024) | Endocrine Society (2018) | |
|---|---|---|
| Cutoff for low total testosterone | Below 300 ng/dL, called a reasonable cutoff | Harmonized lower limit of normal, 264 ng/dL, on a calibrated assay |
| How many tests | Two total testosterone measurements on separate occasions | Initial test confirmed by a repeat |
| Timing | Early morning, same lab and same assay where possible | Fasting, early morning |
| Symptoms | Low testosterone combined with symptoms and/or signs | Symptoms and signs consistent with deficiency plus consistently low levels |
| Free testosterone | Not recommended as the primary diagnostic measure | Recommended when total is near the lower limit or SHBG is altered |
| Next labs after a low result | LH; prolactin if LH is low or low-normal | Further evaluation to find the cause |
| On-treatment target | Middle tertile, 450 to 600 ng/dL | Mid-normal range |
| Testosterone rechecks | 2 to 4 weeks after starting, then every 6 to 12 months | Within the first year as part of a standard plan |
| Hematocrit | Withhold if above 50% before starting; intervene at 54% or higher | Elevated hematocrit is a reason not to start; monitored on treatment |
| PSA | Before starting in men over 40; then shared decision-making | 3 to 12 months after starting; refer if it rises more than 1.4 ng/mL in the first year or exceeds 4.0 ng/mL |
Where the two numbers come from
The AUA guideline states plainly that a total testosterone below 300 ng/dL is a reasonable cutoff. It is a practical line, easy to remember, and close to where many labs set the bottom of their range.
The Endocrine Society’s number comes from a measurement project rather than a round figure. Researchers pooled four large cohorts from the U.S. and Europe and recalibrated their results against a CDC reference method. In that 2017 analysis, the 2.5th percentile for healthy, non-obese men aged 19 to 39 was 264 ng/dL, with a harmonized range of 264 to 916 ng/dL. The same study found that much of the disagreement between cohorts came from assay differences, which is why the Endocrine Society ties its cutoff to an accurate, calibrated test.
So a result of 280 ng/dL can be “low” by one guideline and “low normal” by the other. Neither guideline treats that number as decisive on its own.
Symptoms and repeat testing: where they agree
Both organizations insist on repetition. The AUA calls for two total testosterone measurements on separate occasions, drawn early in the morning, and its follow-up table asks for the same lab and the same assay. The Endocrine Society guideline asks for fasting morning total testosterone measured with an accurate and reliable assay, confirmed by a repeat.
Both also insist on symptoms. The AUA says the clinical diagnosis is made only when low testosterone is combined with symptoms and/or signs. The Endocrine Society goes slightly further, asking for symptoms and signs consistent with deficiency plus unequivocally and consistently low levels. In practice, the symptom list overlaps: low libido, fewer morning erections, fatigue, loss of muscle and mood changes.
The two part ways on free testosterone. The Endocrine Society recommends measuring it, by equilibrium dialysis or an accurate formula, when total testosterone is near the lower limit or when a condition alters SHBG. The AUA panel does not recommend free testosterone as the primary diagnostic measure, though it uses it in specific situations, such as an unexplained rise in hematocrit on treatment. Our page comparing free and total testosterone explains why the distinction matters.
On treatment: targets and monitoring
The AUA sets a specific target: adjust treatment to reach the middle tertile, which it defines as about 450 to 600 ng/dL for most labs. It recommends a first testosterone check two to four weeks after starting, depending on the form of therapy, then every 6 to 12 months. Hematocrit should be under 50% before treatment and checked every 6 to 12 months, with a value of 54% or higher warranting intervention.
The Endocrine Society aims for the mid-normal range and asks clinicians to follow a standardized plan that evaluates symptoms, side effects and adherence, measures testosterone and hematocrit, and assesses prostate cancer risk during the first year. Its guideline summary recommends a PSA check 3 to 12 months after starting and urology referral for a confirmed rise of more than 1.4 ng/mL in the first 12 months or a confirmed PSA above 4.0 ng/mL. It also suggests against routinely treating every man 65 or older who has low testosterone, favoring an individual decision.
Both lists of reasons not to start overlap heavily. The Endocrine Society names, among others, plans to father a child in the near term, untreated severe sleep apnea, uncontrolled heart failure, a heart attack or stroke within six months and a clotting disorder; the AUA likewise advises against testosterone for men currently trying to conceive. Our page on how often to get blood work on TRT turns both schedules into a single calendar.
The 2026 statement: closer to the AUA’s number
In July 2026, the Endocrine Society issued a statement on testosterone therapy rather than a new guideline. It says symptoms alone are not diagnostic, calls for at least two early-morning fasting tests showing consistently low, accurately measured total and free testosterone, and describes a common clinical threshold near 300 ng/dL. It recommends standardized assays certified through the CDC’s hormone standardization program and calls weight loss typically the first-line approach when excess weight is behind low testosterone. Our article on the Endocrine Society’s 2026 statement covers it in full.
What it means if you are in the gray zone
If your morning result falls between 264 and 300 ng/dL, the guidelines point to the same next steps even though they label the number differently: repeat it, check free testosterone and SHBG, look at LH, and look for reversible causes such as weight, sleep apnea, alcohol and medicines. Our page on borderline testosterone levels walks through that workup, and the one on what testosterone level qualifies you for TRT answers the most common version of the question.
A result well above 300 ng/dL with strong symptoms is a different conversation, usually about SHBG, thyroid, sleep or mood. A result well below 264 ng/dL on repeat testing, with symptoms, meets both definitions.
How Ultimate Male applies the guidelines
At our San Gabriel and Downey clinics, labs come first. Through preventative blood testing, morning draws are done on site with results in 24 to 48 hours, and the TRT pre-screening panel covers total testosterone, estradiol, PSA and a complete blood count, with free testosterone, SHBG and LH added when a result sits near either line.
A PA-C or MD explains which guideline thresholds your numbers meet, what a repeat test would add and what else could explain how you feel. Meeting a guideline threshold opens a conversation about treatment; it does not settle it. The free 10-minute phone call at 626-319-5261 is the first step.
