A s a young man, Nick Dooley never thought about his hormones. He always considered himself “quite an outgoing, confident, chatty person”. Around the time he turned 30, however, Dooley began putting on weight and struggling with anxiety, “just slowly becoming a shell of my former self”, he says. By 38, he weighed 22st (140kg) and had a range of health issues. “I spent most of my life sat in front of a TV, doing nothing, with zero motivation, and from how I was in my 20s, that wasn’t me. I knew something wasn’t right.”

In 2024, Dooley had a private medical exam, which flagged he had fatty liver disease and was producing low levels of testosterone. “It wasn’t something I’d ever really heard of,” he says. “So I started down a Reddit rabbit hole.” An NHS doctor told him his blood testosterone levels, at 11.2 nmol a litre, were “within range” (although guidance differs between trusts, NHS England generally considers between 8 and 30 nmol/L normal) and offered him antidepressants. “I knew that wasn’t going to fix me,” he says. Instead, Dooley signed up with Manual, an online men’s health company. After two quick blood tests and a virtual consultation, Manual, which has since rebranded as Voy, started him on testosterone replacement therapy (TRT).

Thanks to TRT, Dooley’s body no longer produces testosterone naturally at all. Instead, he gets his “T” from a vial of testosterone cypionate, injected three mornings a week. “It’s got me back to being myself,” he says. “I don’t suffer from anxiety any more. My depression’s completely gone.” He claims to have lost 45kg. Alongside his day job as a train driver, Dooley is now a TRT influencer, extolling the virtues of testosterone therapy on social media. (He also promotes Voy, which is how I met him.) Testosterone, he says, “changed my life”.

Dooley is far from the only guy shouting about T. On TikTok, fitness influencers extol the practice of “T-maxxing”, maximising their testosterone levels using methods both natural (sleep, diet, exercise) and artificial (steroids). Celebrities from Robbie Williams to Joe Rogan are openly discussing their experiences with TRT. The London underground is plastered with Voy ads: “Feeling irritable? It might be low testosterone.”

Among men, the conversation around T has taken on an almost existential bent. In the rightwing manosphere, “low T” has become an insult on a par with “beta” or “simp”. In October, US health secretary Robert F Kennedy Jr – who, at 72, injects testosterone as part of his personal “anti-ageing regimen” – warned, without evidence, that today’s American teenagers have “50% of the testosterone of a 65-year-old man”. Testosterone, some would have you believe, is at the centre of a full-blown masculinity crisis.

“It’s been a real crescendo,” says Channa Jayasena, an NHS endocrinologist and clinical professor of reproductive endocrinology at Imperial College London. According to NHS data, prescriptions for testosterone in the UK jumped 135% between 2021 and 2024. The figure has also grown sharply in the US, with the largest increases among younger men. Jayasena tells me the trend recently came up at a national training conference for endocrinologists. “Every single group brought it up. They said, ‘We’re seeing more and more of them. They’re clogging up our clinics. What do we do?’”

The spike in demand has coincided with a boom in direct-to-consumer men’s health companies such as Voy, Hims and Numan, which target men via social media ads and offer a one-stop treatment shop for the afflictions of male middle age: erectile dysfunction, hair loss, obesity and low T. Their ubiquity relies in part on a neat loophole: although companies in the UK cannot legally advertise testosterone, which is a prescription drug, they can advertise tests.

Endocrinologists have expressed concern that testosterone deficiency is being overdiagnosed and causing unnecessary anxiety among otherwise healthy men. TRT advocates, on the other hand, argue that testosterone deficiency is widely underdiagnosed, and that the NHS’s outdated approach to hormonal health has led to men being routinely denied life-altering care. Perhaps fittingly for an argument over testosterone, the fight has become fierce, like two T-filled alphas, each seeking to dominate the other.

There’s a reason testosterone is a shorthand for masculinity. “It literally turns boys into men,” Jayasena says. Primarily produced in the testes, T plays a key role in the development of the male anatomy in the womb. During puberty, when testosterone in boys spikes by as much as 3,000%, T triggers the development of male sex characteristics including facial hair and a deeper voice, plus increased red blood cell production, bone density and muscle growth.

“It’s why men tend to be stronger and run faster,” explains Geoff Hackett, a consultant urologist and author of the British Society for Sexual Medicine’s (BSSM) guidance on T. Testosterone is also an anabolic steroid, which is why it has long been banned by the World Anti-Doping Association as a performance-enhancing drug, albeit one favoured in extreme doses by bodybuilders looking to sculpt superhuman physiques.

Women also produce testosterone, via the adrenal glands and ovaries, but at far lower levels. In the UK, T prescriptions for women have risen 10-fold, boosted by celebrity recommendations from Davina McCall, Kate Winslet and Halle Berry, all of whom have talked about their experiences taking it for the symptoms of menopause – although the benefits of this are still being studied. (T also plays a crucial role in trans healthcare.)

The medical term for male testosterone deficiency is hypogonadism, which describes men who cannot produce enough testosterone, because of a physical problem with the testes or a disruption in signalling from the pituitary gland or hypothalamus. But because men’s natural testosterone levels vary so widely, “to have a true diagnosis of male hypogonadism, you need low testosterone, but you also need key symptoms”, Jayasena says. Those include erectile dysfunction – in particular the absence of morning erections – low libido, infertility, weight gain, osteoporosis and depression.

George, a social care worker from Manchester, had long suspected he had a hormone deficiency. “I remember being in the last year of school, doing PE and thinking: I look nothing like anybody else,” he says. He was overweight and had an “extremely low” sex drive, but struggled to get a diagnosis. In his early 20s, after seeing a TRT ad on social media, George took an at-home blood test, which came back on the borderline for NHS treatment. “I took the results to the doctor and was like, ‘I’m considering TRT.’ And the first doctor just laughed at me,” he says. After seeking a second opinion, it emerged he’d been flagged for potential hypogonadism during a routine blood test as a teenager, but had never been told. As soon as he started TRT, George says, “I felt all these changes in myself.” He has lost weight and has more energy. “My confidence has skyrocketed, in a healthy way. At work, my manager said, ‘There’s something different about you.’”

Will started TRT after struggling with depression and erectile dysfunction in his late 20s. “I’d just put it down to not being 18 any more,” he says. But after undergoing surgery for an unrelated injury, he began to suspect something was wrong. “In my operation write-up, they noted one of my testicles had atrophied and was basically dead,” he says. His GP told him his testosterone was still above the threshold for treatment, and offered him antidepressants. “Every time I went to the doctor and said, ‘Can you test me for testosterone?’ I’d either get a flat out ‘No’ or they’d do one test and go, ‘No, you’re fine.’” Eventually, he found a TRT clinic that agreed his results were low enough to prescribe treatment. The impact, he says, has been profound. “It’s like I was wearing a pair of glasses with the wrong prescription; suddenly, all the blurriness lifted.”

While men do not go through menopause, their testosterone levels generally peak in their 20s and fall gradually with age. Historically, this has been an accepted part of ageing, but recently more men – RFK Jr among them – have begun to use T as a kind of longevity drug; a means to loosen the shackles of time.

Matthew, 60, a travel agent from Manchester, started TRT in part because he found he was low on energy and it was affecting his sex life. “I was getting a bit saggy and a bit sad,” as he puts it. “I didn’t want to give up on life.” He buys his T from an “underground” pharmacy and is thrilled with the results. “I’m zipping around, I’m nightclubbing, I’m pubbing. I have a great time.”

Matthew shows me the needles he keeps in his desk. Many men prefer injections to creams or gels due to the longer, more predictable effect. Injecting doesn’t bother Matthew, he says, in part because he used steroids when he was younger. “I didn’t go mad on it. But I did it.”

The difference between TRT and doing steroids, or “juicing”, is essentially one of dose: while TRT aims to keep T within normal boundaries, bodybuilders inject T at levels vastly beyond them, usually in concert with other drugs, to accelerate muscle growth. (Arnold Schwarzenegger has since admitted that his massive 1980s physique was partly a product of using T and a drug called Dianabol.) Studies have shown that, alongside seriously increased risk of heart attacks, steroid abuse can permanently damage both sperm and testosterone production, leading some men to find that when they stop steroids, they end up needing TRT.

Perhaps because of this history, testosterone and steroid communities online often overlap. On TRT forums, I found steroid users sharing advice about side-effects, maintaining fertility and safe “pinning” (injection) practice. “The steroid community has been the most helpful, even when it comes to TRT,” George says. “That’s dangerous, because it can cause a rabbit-hole effect for people.” Sure enough, immediately after I searched for testosterone, my TikTok algorithm started showing me videos of fitness influencers peddling steroid regimens and promoting underground sellers.

Several men tell me the difficulty in getting a diagnosis via the NHS, and the cost of TRT privately, has driven them to self-medicate using these underground labs. Even patients such as Will, who pays for TRT from a licensed clinic, found the NHS’s attitude frustrating. “I shouldn’t have to pay a private clinic £200 a month,” he says. “I’m not a gym ‘juicer’. I’m not using superhuman levels. I take enough to give me a normal level of testosterone and feel like a human being again, because I spent years of my life not feeling like a human being.”

Although nobody would describe me as an alpha male, I’ve never worried about my testosterone levels. Still, for the purposes of this story, I log on to Voy’s website and, after filling out a very broad questionnaire (Am I tired? Am I ever grumpy?) and claiming a 50% discount, I pay £27.50 for an at-home testosterone test. When it arrives, I squeeze a couple of fingers’ worth of blood into the enclosed vial, post it to the lab and forget about it – until a week later, when I receive a surprising email from Voy, informing me “Your free testosterone levels are low”. (“Free” refers to T in the blood that is not bound to other proteins, such as albumin or sex hormone-binding globulin, and is therefore theoretically able to act on other tissues.)

The email throws me. I have been tired lately, and put on weight, which I’d blamed on overindulging at Christmas. Could low T really be the cause? When I read my results in more detail, I’m confused. My “total testosterone”, at 16.4 nmol/L, is well above the cutoff for hypogonadism according to both the NHS (8 nmol/L) and BSSM (12 nmol/L), whose guidelines Voy claims to follow. My supposedly low “free testosterone” is also above their cutoff levels. Still, Voy is urging me to buy a £79.95 “enhanced blood test” to confirm my diagnosis.

I happen to be interviewing Jayasena for this story a few days later, in his office at Hammersmith hospital in London, overlooking a nearby sports field. When I show him my results, he is stunned. “That is just wrong. That – 16! – is amazing. Your levels are fine.” He shakes his head. “That’s absolutely shocking.”

Menwell Ltd, the parent company of Manual/Voy, was founded in 2018 by Michalis Gkontas, a tech entrepreneur who previously ran a food delivery business, and George Pallis, a former head of marketing at Deliveroo. It initially sold treatments for hair loss and erectile dysfunction, but quickly expanded into weight-loss jabs, menopause treatments and TRT. Voy now claims to have more than 1.5 million patients across the UK, Germany and Brazil, and has raised more than $150m (which perhaps explains the tube ads).

When I contact Voy, they set up an interview for me with Dr Jeff Foster, the company’s director of men’s health. A photogenic GP who also runs his own private TRT clinic in Warwickshire, Foster says his interest in testosterone grew from watching what he felt was the NHS failing men with hormone conditions. “A lot of men would come and see me and ask questions about things like erectile dysfunction or testosterone,” he says. “And my answer was, ‘We’ll refer you to endocrine and they’ll tell you the answer’ or, ‘We’ll refer you to urology, and they’ll tell you.’ But they don’t.”

Like other TRT doctors, Foster says he’s worried about a blurring of the lines between TRT and steroid use. “These guys who are ‘T-maxxing’,” he says, “when you see an absolutely stacked 20-year-old on social media who says he’s using TRT, he’s not; he’s using steroids.”

The average Voy patient, Foster says, is between 35 and 55. “We spend a lot of time trying to weed out those who just need to lose a bit of weight, or be a bit healthier.” When asked how many men in Britain actually have low testosterone, Foster is more circumspect. “The honest answer, if anyone tells you they know the prevalence of low testosterone, is they don’t, because the numbers have changed and are changing so rapidly,” he says.

I find this surprising, because Manual’s website clearly states that “one in four men suffer from low testosterone after age 30”. (The company is still in the process of rebranding, so confusingly both the Voy and Manual websites remain live. But Voy’s site repeats the claim, in slightly different wording.) The source of this alarming figure is a paper published nearly 20 years ago in the Journal of Clinical Endocrinology & Metabolism. It is also somewhat misleading. The study, of 1,475 US men, did find that 24.3% of the men had testosterone levels lower than 10.4 nmol/L, but the number who actually had symptoms – and were therefore diagnosable with hypogonadism – was just 5.6%, and the majority of those men were over 70. More recent studies in Europe, the US and China have repeatedly found that hypogonadism affects between 2% and 8% of men, with risk increasing with age.

Foster is undeterred. “We used to think testosterone deficiency was something that should only be treated when it’s really, really bad. Like, if we lop off your nuts, you need testosterone,” he says. “But we have increasing evidence that people benefit from higher levels.”

When I ask Foster about my results, he pulls them up on his screen. “Your total T was 16, which was absolutely fine, and your free T was 0.26, which is lowish, but again, some guidance says it’s OK,” he says. “This is where you weed it out in the second test.” So, a few days later, I pay £79.95 for Voy’s “enhanced” test, and drive to a nearby pharmacy to have my blood taken. I also order a fingerprick test from Medichecks, another testing company, to compare results.

Soon, my Voy results come back again. This time, both my total T and free T are flagged as low. My total has fallen slightly; my free has increased. Both are still above the thresholds for testosterone deficiency as defined by the NHS and the BSSM – as well as the Endocrine Society, the American Association of Clinical Endocrinologists, the American Urological Association and the International Society for Sexual Medicine.

Nonetheless, Voy is now urging me to buy a doctor’s consultation for another £79.95, taking the total spend to more than £180. The “doctor’s recommendation” page disclosing this news, complete with a headshot of Foster, repeats the one-in-four claim and promises that I “could see an increase [in T] in just six weeks”.

The closer I look, the more uneasy I feel. The TRT section of Manual’s website includes a video testimonial from “Ali, 34”, who I discover is one of the brand’s senior employees. According to the Advertising Standards Authority, brands should not “falsely claim or imply” that employees are consumers. (Menwell, which has been penalised by the ASA three times for breaches of advertising standards, confirms that “Ali is an employee at Voy, alongside being a paying Voy TRT patient”, and that the video was a “personal account”.)

After some searching, I find a page on Manual’s website explaining that it uses 15 nmol/L as its threshold for low T diagnosis, along with a different cutoff for free T. That is despite the small print under my “detailed results” which states that “testosterone levels higher than 12 nmol/L usually do not require any treatment”.

This isn’t the first time the company has taken a somewhat loose approach to accepted definitions of low testosterone. As Manual, Voy previously flagged total T results as high as 17 nmol/L as “suboptimal”, a term without any clear clinical definition. “We did have that word in the bloods a while back,” Foster tells me, sheepishly. “I’ve got rid of that because I don’t like the idea; either it’s low or it’s not.” (His forthcoming book on testosterone, due to be published by HarperCollins in July, is titled Optimal. He says he wants to change it.)

When challenged, Foster seems to wobble. “There is an optimal range for testosterone,” he continues. “We know that if you keep your testosterone in that normal range – we’ll say 15 to 30 nmol/L, assuming your free T is normal – then your all-cause mortality is less.” I can’t find studies to back up that claim, nor does Voy provide them when asked. More broadly, the evidence for the benefits of testosterone use in otherwise healthy men is mixed, though research has indeed found men with diagnosed hypogonadism have a higher mortality risk.

“Some endocrinologists say, ‘You’re just medicalising normal health and you shouldn’t be doing this,’” Foster says. “And I don’t think we should be treating every guy, because as soon as you do that you lose credibility. But you also want to be progressive, especially when the evidence suggests you can benefit with treatment.”

This approach is controversial to say the least. “They’ve invented a spurious pseudo-disease called ‘low testosterone’ from which vast numbers of men are said to suffer,” says Dr Richard Quinton, a consultant endocrinologist and a co-author of the Society for Endocrinology’s guidelines on testosterone replacement.

A sceptic might suggest that, for companies selling testosterone, widening the definition of testosterone deficiency gives you the largest market possible. This, Quinton suggests, is a broader risk facing the TRT industry. “Private equity has dumped a vast amount of money into testosterone clinics around the UK, and it obviously wants to see a return on that money.”

Advocates of broadening the definition of low T simply point to the stories of men such as Nick, George and Will, who were turned away for treatment but benefited from TRT privately. “I’ve spoken to at least 200 patients who have gone through the NHS, and when they contact us some of them are on the brink of tears because they’re not getting the help they need,” says Richie Gibbs, founder of the TRT clinic Origin.

The pro-T camp is quick to point out that testosterone is safe and previous evidence linking T to a higher risk of prostate cancer and heart attacks has been downplayed by more recent studies. But Quinton emphasises that those studies did not apply to men injecting T beyond natural levels: “We know absolutely that if you’re taking excessive amounts of testosterone, your risk of heart disease and heart events is significantly increased.”

Testosterone abuse has other side-effects. Taking T significantly suppresses the testes’ natural production, affecting fertility (though this is usually reversible and the risk can be mitigated with medication). It can also cause blood thickening, atrophying of the testes, acne and hair loss. Then there are the psychological effects: at very high doses, T abuse has been linked with severe mental health conditions. “It acts on the limbic system of the brain to trigger psychosis,” Jayasena says.

For some men, the psychological impacts of T are part of its appeal. Many told me they felt more confident, or more competitive, on it. “When I first went on it, the first day or two after injection I’d be very argumentative, very aggressive,” Matthew says. “I think they call it ‘roid rage’. I definitely know what they mean.”

Until recently, testosterone was thought to increase risk-taking behaviour. Scientists now understand it encourages “status-seeking behaviour” and makes men more reactive to challenges to that status (ie, rather than turning men into alphas, T-maxxing might just increase your likelihood of becoming a thin-skinned podcaster).

There are other, subtler effects of the debate around T. When I got my Voy results, I found the thought of having low T unexpectedly emasculating. For the first time in my life, I started worrying about my erections. Was low T behind my past mental health struggles? Or my middling gains at the gym? More to the point: if I did have low T, did that make me less of a man?

This stigma came up regularly in conversations with men for this story; many asked not to use their real names, due to the negative associations. In January, a paper published in the journal Social Science & Medicine found that social media posts about testosterone were contributing to the “medicalisation of masculinity”. “I felt quite ashamed,” George says, “to think I hadn’t got enough of the only chemical that defines me as a man.”

This anxiety around testosterone is happening at the same time as a broader social anxiety around men as a group. Alongside declining sperm counts, some population studies have found that average testosterone levels have fallen over time (although the extent of the fall is debated). Experts have speculated that any wider fall in T might be linked to our more sedentary lifestyles, or exposure to endocrine-disrupting chemicals. The most obvious suspect is obesity, which today affects about 30% of British people and 40% of Americans. There, the link is clearer: adipose fat aromatises testosterone into estradiol, a form of oestrogen, triggering weight gain. Numerous studies have shown that losing weight can raise testosterone significantly, and that weight-loss jabs can be effective in raising T levels among obese men without the need for TRT.

Nick, the train driver, has ruminated on his low T diagnosis coming soon after he was diagnosed with fatty liver disease. “Was I fat so I had low testosterone, or was my low testosterone causing me to be fat? It’s a chicken and egg question,” he says. Like most men who start TRT, it’s likely Nick will be on T for the rest of his life. At more than £100 month, that’s a considerable expense. But he considers his new life worth it. “It’s like a second puberty. It got me back to having the libido of a 20-year-old, chasing my wife around the house.”

I don’t end up paying for a consultation with Voy. My Medichecks test result comes back and reassures me that my testosterone levels are “within normal range”. But looking at my social feed, now crowded with ripped young men hawking T, I can see the appeal. After my results, I find myself thinking about T where I wouldn’t before: in the gym, making dinner. I start taking a zinc supplement. I’m eating more meat. At one point in my conversation with Foster, I raised the idea that advertising around low T could plant unnecessary fear in men’s minds. He conceded that ads are a blunt instrument. “We’re trying to promote awareness around a condition that is really poorly understood. You are going to get people who are not ever going to be eligible, who think they’ve got low testosterone, but the beauty is they’ll be screened out. So they’ll be pissed they paid £35 for a test, but they won’t be falsely treated.”

Foster says 2,000 to 3,000 patients are entering what he terms Voy’s “funnel” every month, although not all of them will end up on TRT. “The conversion rate is less than 20%,” he says. After the second test, this increases dramatically. “Usually, about 70% to 80% will start treatment if you get them to consultation.” It felt a little strange to hear a doctor speaking in the language of a marketer. I couldn’t shake the sense I was being seen less as a patient than a customer being moved down that funnel, whether I needed it or not.

Some names have been changed.