“Low T” Isn’t a Diagnosis

You have almost certainly heard the phrase "Low T." It's been on the radio, on television, and on billboards for years, and now it fills social media feeds and the ads of men's-health clinics promising to restore your energy, your libido, and your edge. As common as it is, you'd be forgiven for assuming "Low T" is a diagnosis, a condition defined by impartial researchers studying patients over years. Except it's not. It's a marketing phrase, one that traces back to a pharmaceutical campaign built to sell a product.

The term was popularized in the early 2010s through "disease awareness" advertising funded by the makers of the leading testosterone gel. These campaigns were clever: by never naming a specific drug, they sidestepped the strict rules the FDA applies to branded prescription-drug ads, which don't generally govern unbranded "awareness" campaigns [1, 2]. Instead of selling a product, they looked to generate concern. Websites hosted "Is It Low T?" quizzes and urged men to "talk to your doctor" and "get tested" if they felt tired, gained weight, or noticed a lower sex drive [1, 3]. Physicians and researchers at the time called it what it looked like: disease-mongering [2, 3].

The symptoms these campaigns fish for are fatigue, low energy, weight gain, low libido, low mood, and trouble concentrating. Do any of those sound familiar? Of course they do. That is precisely the point: these symptoms are nearly universal, and they overlap with dozens of causes other than low testosterone. The realities of modern life leave many of us overworked, financially stretched, overly stressed, poorly rested, sedentary, and nudged toward convenient, less healthy food choices; any one of which can produce that exact list of symptoms (and, as we will see, can cause testosterone levels to drop in the first place). So the marketing found fertile ground: it offered a hormonal explanation, and a hormonal fix, for symptoms that usually have very different roots.

So, let's discuss testosterone. I'll walk through what the science actually recognizes, why so much testosterone is being prescribed today, and why a more conservative approach is usually the better one. Let's start with what "low testosterone" actually means in medicine.

Two very different things get called "low testosterone"

Medicine recognizes two distinct categories, and collapsing them together is the central confusion behind "Low T."

Organic (classical) hypogonadism is a permanent, structural disease of the system that produces testosterone: the testes, or the pituitary and hypothalamus in the brain. Causes include Klinefelter syndrome (a genetic condition present from birth), damage to the testes from injury or chemotherapy, and pituitary or hypothalamic tumors, for example [4]. This is real, sometimes serious, and testosterone therapy is genuinely and uncontroversially indicated. It is also rare, affecting well under 1 in 100 men [4].

Functional hypogonadism is defined as low testosterone on repeated testing, together with symptoms, but without any structural disease of the testes or brain to explain it. In other words, the machinery is intact, but something is suppressing it, so the low level is a symptom of something else rather than a permanent disorder in itself. By far the most common driver is excess body fat and the metabolic problems associated with it, such as insulin resistance and type 2 diabetes. It can also be caused by certain medications (opioids and corticosteroids in particular), serious acute or chronic illness, heavy alcohol use, and, ironically, prior use of testosterone or anabolic steroids, which suppress the body's own production [4]. Functional hypogonadism affects an estimated 2–8% of men, and its prevalence climbs steeply with body weight: roughly 0.4% in men of normal weight, 1.6% in the overweight range, and 5.2% in men with obesity [4].

A quick word on BMI, since it will likely come up often in my blogs: it remains the most widely used screening tool for obesity because it is simple to calculate and correlates well with body fat at the population level. However, it has significant limitations: it cannot distinguish fat from muscle, misses about half of people with excess body fat [5], doesn't account for where fat is stored, and its accuracy varies by sex, age, and ethnicity. For an individual patient, BMI can be misleading — two people with the same BMI can have very different amounts of body fat and very different health risks.)

The takeaway is simple: true, permanent testosterone deficiency from disease of the testes or brain affects fewer than 1 in 100 men. The far more common scenario, low testosterone driven by weight, medications, or other health conditions, is not a permanent hormonal disorder but a signal that something else needs to be addressed first. By definition, functional hypogonadism is potentially reversible when you treat the cause, and clinical guidelines uniformly recommend doing exactly that before reaching for testosterone.

Why the test itself is so easy to get wrong

Even when testing is appropriate, testosterone is a genuinely tricky measurement, and the convenient at-home or clinic tests get it wrong constantly.

Levels follow a daily rhythm, peaking in the morning, so an afternoon draw can read 20–25% lower in younger men [6]. Food, especially sugar, temporarily suppresses the number, so testing should be done fasting [7]. Any acute illness pushes it down. And levels vary enough day to day that a single result means little. Proper diagnosis requires at least two separate early-morning, fasting measurements, ideally using a high-quality lab assay, together with the actual symptoms of testosterone deficiency: not a vague off day, but a consistent pattern such as reduced libido, erectile changes, or loss of morning erections persisting over time [7]. A single afternoon, non-fasting, mail-order test, taken without any of that context, is close to meaningless. Yet that is exactly what much of the "get tested" ecosystem runs on.

There's one more wrinkle the cheap tests miss. Most testosterone in the blood is bound to a protein called SHBG, and obesity lowers SHBG, which can drag down your total testosterone reading while your free testosterone (the biologically active part) stays perfectly normal. A man in this situation can be flagged as "deficient" by a total-testosterone test when he doesn't actually have a deficiency at all [4]. It's a good example of why a lone number, absent the full clinical picture, tells you little.

How we ended up with a prescribing boom

Testosterone prescribing has surged, and it hasn't been driven mainly by new cases of real disease. Between 2018 and 2022, the share of people filling testosterone prescriptions rose sharply, and the growth was steepest among the youngest men: roughly 120% in men 24 and under and 86% in men 25–34, versus about 12% in men 65 and older [8]. That's a concern not because young men can't have a genuine problem, but because these are the men with a lifetime ahead of them to accumulate the risks of long-term therapy, and the ones most likely to have a reversible cause driving a low number in the first place. They stand to gain the least and be exposed the longest.

Several forces enabled this. Prescribing a drug "off-label," outside its approved use, is legal; telemedicine rules for controlled substances loosened during the pandemic, making remote prescribing far easier; and compounding pharmacies alongside a wave of subscription-based online men's-health clinics made access frictionless. For many of those clinics, prescribing is the business model, and the "Low T" vocabulary that AbbVie pioneered is now simply the native language of the sector: today's largest telehealth brands market directly to the same fatigue-and-libido symptom cluster, sell at-home test kits, and ship treatment to your door. A 2026 analysis of 253 websites offering testosterone found widespread claims that run against clinical guidelines: about 20.6% claimed testosterone lowers cardiovascular risk, 9.9% offered it to men with normal testosterone levels (why bother checking?), 9.9% promoted anti-aging effects, and 11.9% pushed "microdosing". The study's authors concluded these represent frequent breaches of advertising law with real potential to harm [9]. Perhaps the most telling statistic came from the FDA itself years earlier: about a quarter of men who received a testosterone prescription had never had their hormone level checked at all [2].

The benefits are narrower than the ads suggest

Set aside the marketing and look at the best evidence. The Testosterone Trials, a coordinated set of NIH-supported, placebo-controlled studies in older men with genuinely low levels, found that testosterone produced a moderate improvement in sexual function, but no meaningful improvement in vitality or energy (only a slight lift in mood) and no improvement in cognition [10, 11]. So even in the men who should respond best, the payoff is modest and mostly limited to libido, not the sweeping restoration of energy and focus the ads imply.

The real risks, starting with fertility

This is the part I most want men to understand before they "just try it."

Testosterone therapy can cause infertility, sometimes irreversibly. Taking testosterone shuts down the body's own signal to produce it, which suppresses sperm production and can shrink the testes. Fertility often recovers after stopping, but recovery can take many months and is not guaranteed [12]. Giving testosterone to a man who hopes to father children is, in effect, backwards.

Beyond fertility, one major potential side effect of testosterone is that it thickens the blood by stimulating red-cell production (polycythemia), which raises clotting risk. Even the large "reassuring" safety trial discussed below showed more atrial fibrillation, pulmonary embolism, and acute kidney injury in the testosterone group [13, 14]. The FDA also recently added a warning that testosterone products raise blood pressure across the board [15].

The trap: it can become self-fulfilling

It isn't intuitive, but taking testosterone for even an intermediate amount time can commit you to it for the long haul. Because exogenous testosterone suppresses your own production, your natural level stays low as long as you're on it. A borderline or even artificially "low" reading, the kind a bad test produces, can quietly become a genuine dependency on the drug. And this is not a supplement you casually stop and start. Testosterone is a controlled substance that requires indefinite monitoring of your blood count and other markers, the kind of follow-up the quick-prescribe clinics are frequently criticized for neglecting [16].

"But didn't the FDA just say it's safe?"

It's a fair question, and worth answering plainly. In February 2026, after reviewing a large trial called TRAVERSE, the FDA removed the boxed cardiovascular warning from testosterone labels [15]. That sounds like a clean bill of health, but the study behind it deserves a closer look.

To its credit, TRAVERSE was a large, randomized, placebo-controlled trial with adjudicated cardiovascular endpoints, which is about as rigorous a design as this question allows. But it carried some real limitations. It was designed only to rule out a 50% increase in cardiac events, meaning it was built to show testosterone isn't dramatically dangerous rather than to prove it's safe (a more moderate 15–20% increase in risk could pass right through that design undetected) [14]. It studied only men with properly confirmed hypogonadism, using a conservative dose of transdermal gel (one of many forms and concentrations of the drug) [14]. And, it was funded by an industry consortium led by testosterone manufacturers [14]. None of that makes TRAVERSE a bad study, but its scope is fairly narrow compared to how and for whom testosterone is used writ large, and there is certainly room for scrutiny given that it’s sponsored by entities who stand to benefit from favorable results.

Perhaps a more representative study would be a large 2026 retrospective cohort which followed more than 350,000 men who started testosterone, over a third of whom had no evidence of hypogonadism at all. Compared with men who had a clinical diagnosis of hypogonadism, those treated without one had a 51% higher rate of major cardiac events and nearly double the death rate over ten years [18]. This study, notably, was not industry-funded. Its authors concluded that testosterone's cardiovascular safety is "context-dependent and less favorable when treatment is initiated without evidence of hypogonadism" [18].  A review of the overall research seems to suggest that it is better to exercise caution and discretion when considering testosterone therapy.

What actually helps

If your testosterone is low because of how you're living, the effective treatment is to address the cause, and the data here are genuinely encouraging.

Weight loss is the single most powerful lever. In pooled studies, a low-calorie diet raised testosterone by an average of about 72 ng/dL, and the substantial weight loss from bariatric surgery raised it by about 207 ng/dL [4]. For comparison, testosterone therapy typically raises levels by 200–400 ng/dL. In other words, meaningful weight loss can move your testosterone into a range comparable to what the gel achieves, while also delivering the metabolic, cardiovascular, and longevity benefits that testosterone therapy does not. The effect tracks with how much weight you lose, and meaningful recovery generally starts once you've lost around 5–10% of your body weight [4]. Surgery isn't the point, the mechanism is the weight loss itself.

This is also where the newer weight-loss medications come in. In a 2025 study of men with obesity and functional hypogonadism, the GLP-1-based drug tirzepatide produced greater weight loss, a larger rise in the body's own testosterone production, and better sexual function than testosterone therapy did, and unlike testosterone it restored the natural hormonal axis rather than shutting it down [19]. That study was small and short, so it isn't the final word, but it points in the same direction as everything else here: fix the metabolic problem, and the testosterone tends to follow.

Beyond weight, the fundamentals all matter and reinforce one another: prioritizing sleep (and getting evaluated for sleep apnea, a common and treatable culprit), regular physical activity including resistance training, moderating alcohol, reviewing any medications that may be suppressing your levels, and managing underlying conditions like diabetes. None of these carry the risks of testosterone therapy, and every one of them improves your health broadly rather than masking a symptom.

And this, finally, is the uncomfortable point behind the whole "Low T" phenomenon: there is no subscription revenue in advising a man to lose weight, sleep more, and drink less. The intervention with the best evidence is the one nobody profits from.

The bottom line

"Low T" is a phrase you've heard everywhere, attached to a number that is remarkably easy to get wrong, sold as the cause of symptoms that usually come from somewhere else entirely. Genuine testosterone deficiency is real and treatable, and if you have it, we should treat it. But for most men, that number never needed checking in the first place, and a low reading is a signal to look at weight, sleep, stress, diet, and exercise rather than a reason to start a lifelong drug with real risks.

If you've had a testosterone result that worried you, or you're being encouraged to start therapy by an outside clinic, bring it to your Primary Care Provider’s attention and consider the whole picture together before you commit to anything.

This post is for general education and is not a substitute for individual medical advice. Your circumstances may differ, so please reach out to discuss your specific situation with your provider.

References

1. Singer N. Selling That New-Man Feeling. The New York Times. 2013. Coverage of AbbVie's unbranded "Low T" disease-awareness campaigns (IsItLowT.com, DriveForFive.com) and the FDA's regulatory distinction between branded and unbranded advertising.

2. Weintraub A. Why All Those Testosterone Ads Constitute Disease Mongering. Forbes. 2015. Includes the FDA finding that roughly a quarter of men prescribed testosterone had not had their levels tested; Perls & Handelsman editorial, Journal of the American Geriatrics Society.

3. Gorski D. "Low T": A pharmaceutical company-invented diagnosis whose purpose is profit. Science-Based Medicine / ScienceBlogs. 2013.

4. Anawalt BD, O'Connor KM, Grossmann M. Adult Male Hypogonadism. JAMA. 2026;335(24):2146. Review covering the organic vs. functional classification, prevalence figures (including BMI-stratified prevalence and the 2–8% functional estimate), the SHBG/pseudo-hypogonadism issue, and pooled diet (~72 ng/dL) and bariatric surgery (~207 ng/dL) effects on testosterone.

5. Okorodudu DO, Jumean MF, Montori VM, Romero-Corral A, Somers VK, Erwin PJ, Lopez-Jimenez F. Diagnostic performance of body mass index to identify obesity as defined by body adiposity: a systematic review and meta-analysis. International Journal of Obesity. 2010;34(5):791–799. (Pooled sensitivity 50%, specificity 90% for detecting excess body fat across 32 samples, n≈31,968; cited in the American Heart Association's 2011 scientific statement on assessing adiposity.)

6. Brambilla DJ, et al. The Effect of Diurnal Variation on Clinical Measurement of Serum Testosterone. J Clin Endocrinol Metab. 2009;94(3):907–913.

7. Bhasin S, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.

8. Selinger S, Thallapureddy A. Cross-sectional analysis of national testosterone prescribing through prescription drug monitoring programs, 2018–2022. PLOS One. 2024;19(8):e0309160.

9. Grant B, de Silva NL, Gumssani M, et al. Discordance Between Online Information and Male Hypogonadism Clinical Guidelines: A Global Multilingual Content Analysis. J Clin Endocrinol Metab. 2026;111(6):1651–1663.

10. Snyder PJ, et al. Effects of Testosterone Treatment in Older Men (The Testosterone Trials). N Engl J Med. 2016;374:611–624.

11. Snyder PJ, et al. Lessons From the Testosterone Trials. Endocrine Reviews. 2018;39(3):369–386.

12. Crosnoe LE, Grober E, Ohl D, Kim ED. Exogenous testosterone: a preventable cause of male infertility. Transl Androl Urol. 2013;2(2):106–113.

13. Testosterone Therapy: Review of Clinical Applications. American Family Physician. 2017;96(7):441–449.

14. Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). N Engl J Med. 2023;389:107–117.

15. U.S. Food and Drug Administration. FDA issues class-wide labeling changes for testosterone products (following the TRAVERSE trial and ambulatory blood pressure monitoring studies). FDA Drug Alerts and Statements, February 2025.

16. Mulhall JP, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline. J Urol. 2018.

17. Yeap BB, et al. Testosterone therapy in older men: clinical implications of recent landmark trials. Eur J Endocrinol. 2024;191(1):R22.

18. Off-label testosterone therapy is associated with higher long-term cardiovascular risk in men. eBioMedicine. 2026. Retrospective cohort of 358,957 testosterone initiators (35.4% without evidence of hypogonadism); off-label use associated with higher MACE (HR 1.51) and all-cause mortality (HR 1.90) over up to 10 years.

19. Cannarella R, et al. Tirzepatide improves body composition, testosterone, and sexual function in men with obesity and metabolic (functional) hypogonadism. Reproductive Biology and Endocrinology. 2025;23(1):92. (Small, short-duration study; tirzepatide outperformed transdermal testosterone on weight loss, endogenous testosterone, and erectile function while restoring rather than suppressing the gonadal axis.)