Testosterone Deficiency & Low Testosterone

Independent specialist assessment and treatment in London, Marylebone W1

There's a lot of noise about testosterone right now — adverts on every underground station, contradictory advice online, and a growing sense among many men that something isn't right but not always a clear path to finding out what.

As a private testosterone specialist in London with no financial interest in prescribing, my goal is simple: work out what's actually going on for you, and find the right path forward — whether that turns out to involve testosterone or not.

I see patients at Central Health London, 23 Devonshire Place, Marylebone, London W1G 6JB, close to Harley Street in the West End. Video consultations are available for patients across the UK and internationally.

Listen to Dr Ben Davis talk with Tom Nicholas on testosterone deficiency and online testosterone clinics

Dr Ben Davis talks with Jon Dean about Testosterone Replacement Therapy and Low Testosterone

What is Testosterone Deficiency?

Testosterone deficiency — also called hypogonadism, testosterone deficiency syndrome (TDS), low testosterone, or low T — is a clinical condition in which the body produces insufficient testosterone to meet its needs. You may also have encountered the terms andropause or male menopause, though these are informal rather than medical descriptions of the same underlying process.

Testosterone plays a central role in sexual desire and function, mood and energy, muscle mass and bone density, and metabolic and cardiovascular health. A low blood test result alone does not make a diagnosis. Testosterone deficiency requires a combination of symptoms and consistently low testosterone levels — confirmed on at least two separate occasions. This distinction matters enormously, and it's one many clinics overlook.

Symptoms of Low Testosterone

The three symptoms most specifically associated with testosterone deficiency are:

  • Loss of sexual desire (reduced libido)

  • Difficulty getting or maintaining erections

  • Loss of morning erections

Other common symptoms include fatigue and low energy, low mood or depression, anxiety and poor concentration, loss of muscle mass, increased body fat (particularly around the abdomen), hot flushes, reduced body hair, and poor sleep.

These symptoms overlap considerably with depression, thyroid disorders, sleep problems, and relationship or psychological difficulties. That overlap is one of the most important reasons why careful, unhurried clinical assessment matters more than a quick blood test and a prescription.

What causes Testosterone Deficiency?

There are lots of different causes of testosterone deficiency and a low testosterone level. A single low testosterone reading doesn’t mean you have testosterone deficiency.

Causes of testosterone deficiency include:

  • Primary or testicular causes

    Including previous infections, testicular cancer including it’s treatment, testicular injuries, haemochromatosis, Klinefelter’s

  • Secondary or hypothalamic-pituiary causes

    Prolactinomas, medications, previous anabolic steroid use, Kallman’s syndrome

  • Functional causes

    Increasingly common — no structural problem with the testes or pituitary, but testosterone is suppressed by obesity, chronic illness (such as type 2 diabetes or HIV), ageing, poor sleep, or long-term physical or psychological stress. Functional testosterone deficiency is the category most often oversimplified or overlooked. In many cases, addressing the underlying cause can raise testosterone meaningfully without medication — which is always worth exploring first.

    Testosterone levels do gradually decline with age, but for many men this doesn’t cause a problem, for others it reaches a point where they have symptoms, which many men are unaware relate to their testosterone levels.

Accurate diagnosis and thinking about underlying causes of low testosterone rather than just treating symptoms is important.

How is Testosterone Deficiency diagnosed?

An accurate testosterone blood test is the starting point, but diagnosis requires considerably more. British Society of Sexual Medicine (BSSM) guidelines recommend at least two morning blood tests — taken before 11am, on separate occasions 4–12 weeks apart — measuring both total testosterone and free testosterone (calculated via SHBG).

As a clinical guide: men with symptoms and a total testosterone below 8 nmol/L are likely to benefit from treatment. Those with levels between 8–12 nmol/L are in a clinical grey zone, where a carefully monitored trial of treatment may be appropriate. Above 12 nmol/L, testosterone is less likely to be the primary cause, and other explanations deserve attention.

Raised SHBG — common in older men and those with certain conditions — can make a "normal" total testosterone misleading. Free testosterone is the biologically active fraction, and is often the more relevant number.

Why the same testosterone level affects men differently: androgen receptor sensitivity and CAG repeats

One of the most frequently overlooked aspects of testosterone assessment is that the same blood result can mean very different things in different men. Two men with identical total testosterone levels can have entirely different clinical experiences — one feels well, the other has clear symptoms of deficiency. Part of the explanation lies in androgen receptor sensitivity: how responsive each man's cells are to the testosterone in his bloodstream.

A key genetic factor is CAG repeat length in the androgen receptor (AR) gene. This gene contains a variable number of repeating sequences of cytosine, adenine, and guanine — CAG repeats. The length of this sequence influences androgen receptor sensitivity:

Shorter CAG repeat lengths are associated with a more sensitive androgen receptor. Men with shorter repeats may feel the effects of testosterone strongly and may be more susceptible to androgenic side effects.

Longer CAG repeat lengths are associated with a less sensitive androgen receptor. Men with longer repeats may require higher testosterone levels to experience the same biological effect — and may have clear symptoms of deficiency even when their blood levels appear within the normal range. This can partly explain why some men with levels of 12–15 nmol/L report significant symptoms while others at the same level feel perfectly well.

CAG repeat analysis isn't part of routine assessment, and it doesn't change the diagnosis on its own. But in complex or ambiguous cases — where the clinical picture doesn't fit the numbers — it adds a valuable layer to the assessment. I consider it alongside free testosterone, SHBG, and a full clinical history.

This is one of many reasons why testosterone assessment should never be reduced to a single number on a blood test.

How is Testosterone Deficiency treated? What is Testosterone Therapy (also known as TRT)?

There is no single right answer. Treatment depends on the cause of your low testosterone, your symptoms, your priorities, and your health as a whole.

Lifestyle and optimisation

For men with functional causes, addressing weight, sleep, alcohol, stress, and underlying health conditions can meaningfully raise testosterone levels. This is always worth exploring, and for some men it is sufficient.

Fertility-preserving approaches

For men who want to maintain their fertility, medications that stimulate the body's own testosterone production — such as clomiphene citrate or hCG — can be an effective alternative to direct testosterone replacement.

Testosterone replacement therapy (TRT)

For men with confirmed testosterone deficiency, TRT can be genuinely life-changing. It is not, however, a straightforward prescription — the preparation, dose, and monitoring schedule all need individual consideration, and it takes time to get right.

Treating the underlying cause

Where low testosterone is secondary to another condition — a prolactinoma, post-steroid hypogonadism, or a correctable metabolic issue — addressing the root cause may be the most appropriate first step.

Types of testosterone replacement therapy: what are the options?

Once a decision to treat is made, choosing the right preparation is worth taking time over. There is no universally best form of TRT — the right choice depends on your lifestyle, how you absorb and respond to testosterone, your preference around needles and daily routines, and how your body responds over time.

Testosterone gels and creams (topical testosterone)

Applied daily to the skin. Examples include Testogel and Testavan. Often underrated — many men do very well on topical preparations. Advantages include no needles, lower risk of raised oestrogen or haematocrit, and strong long-term cardiovascular safety data (the TRAVERSE study). The main drawbacks are the need for daily application and the small risk of transfer to a partner or child. Cost: approximately £45 per month for a standard dose.

Testosterone Cypionate (injection)

A single testosterone ester giving predictable, stable levels. Can be injected subcutaneously (into fat) rather than intramuscularly, which many men find easier. Olive oil carrier causes fewer local reactions. Used off-licence in the UK (imported from the USA). Cost: approximately £215 per four months, plus injecting equipment.

Testosterone Enanthate (injection)

Another single ester, suitable for microdosing (typically twice weekly). Intramuscular injection only. Castor oil carrier can cause more localised reactions in some men. Cost: variable, up to £60 per month.

Sustanon (injection)

A blend of four testosterone esters, UK-licensed and the most affordable option. Licensed at three-weekly intervals, but most men do considerably better with microdosing — once or twice weekly — to avoid the symptom dip that tends to occur in the third week. Cost: approximately £10 per month.

Nebido — testosterone undecanoate (injection)

Long-acting: one injection every three months once stable. Very convenient for men who dislike frequent injections. The trade-off is reduced flexibility — once injected, the dose is fixed for three months, and levels fluctuate over that period. Cost: approximately £100 per three months.

Kyzatrex (oral testosterone undecanoate)

This is a new treatment, which involves taking testosterone capsules by mouth twice a day. It is good for men who don’t like injections and for whom gel hasn’t worked. It’s quite expensive, depending on the strength and dose, and can cost £200-300 per month.

Some men start on one preparation and switch after a few months if it isn't working as hoped. This is normal and expected. Getting the right treatment takes time and attention — which is another reason why continuity of care with a single doctor matters.

Read my detailed guide to all types of TRT, including full pros, cons and costs here

Why I work independently — and what that means for you

I haven't always worked independently. Earlier in my career I worked within bigger online testosterone clinics — and I've been approached more than once about senior clinical roles at large online testosterone providers. I've said no to many of these, and the reason is straightforward.

The business model of most testosterone clinics, online or otherwise, is built around subscription-based prescribing. The financial incentive is to diagnose testosterone deficiency and keep men on a monthly prescription. That model works well for generating revenue. It doesn't always work well for men.

The problem isn't that testosterone therapy doesn't help — for the right men, it absolutely does. The problem is that not every man presenting with fatigue, low libido, and mood difficulties actually has testosterone deficiency as the primary cause. Sometimes it’s more complex, it’s untreated sleep apnoea, or coeliac disease, or anaemia from bowel cancer.

But when you're running a clinic with a subscription model, there is pressure — however subtle — to fit men into the box that generates a prescription.

What brought me back to independent practice was the men I couldn't adequately help within that model: men who had been on TRT for years but whose symptoms had never fully resolved. Men whose testosterone had been optimised repeatedly, but who were still struggling — because the real issue was psychological, relational, or rooted in something else entirely. As a clinical sexologist and GP, I can do what a testosterone clinic cannot: assess the full picture, use the full breadth of my medical training, not just a testosterone prescriber, and be honest when testosterone isn't the answer.

That independence also shapes how I prescribe. I don't prescribe testosterone to men where I don’t think it’s likely to help them. But I also work with men to find a solution which works for them. I don't run a subscription model. I run a clinical practice — where the aim is to find the right answer for you, monitor you properly over time, and help you move toward better health, not just better numbers on a blood test.

If you've been told by an online clinic that your testosterone is low and you need TRT, or if you've been on TRT for a while without feeling better, I'd encourage you to get an independent second opinion. That's exactly the kind of conversation I'm here to have.

Why choose Dr Ben Davis as your testosterone specialist in London?

My qualifications are among the strongest of any private men’s health specialist in London:

  • FECSM — Fellow of the European Committee of Sexual Medicine (the highest European qualification in sexual medicine)

  • MRCP — specialist training in internal medicine

  • MRCGP — qualified GP

  • PhD in men's emotional and sexual health (University of Cambridge and UCL)

  • Registered with COSRT as a sex and relationship therapist

  • Member of the British Society of Sexual Medicine (BSSM) committee

Without being arrogant (!) this breadth is unusual. Most testosterone clinics focus solely on hormones. I assess the full medical, psychological, and relational picture — and can provide integrated care that includes psychosexual therapy where relevant. I see men of all sexual orientations. As a gay man myself, I understand the specific concerns that may bring gay and bisexual men to seek care, and offer a genuinely open, non-judgmental space.

What to expect:

  • A 60-minute initial consultation covering your full medical, hormonal, and sexual history

  • Comprehensive blood tests, covering more than just hormones

  • At least four follow-up appointments in year one (at 1, 3, 6, and 12 months), and contact with me throughout as needed

  • All appointments directly with me — no handoffs to nurses or case managers

  • Time to explore concerns that go beyond blood results

Frequently Asked Questions

  • The most specific symptoms are loss of sexual desire, difficulty getting or maintaining erections, and loss of morning erections. A blood test measuring total and free testosterone, taken before 11am on two separate mornings several weeks apart, is required for diagnosis. A single low result is not sufficient.

  • ISSM, EAU and BSSM guidelines suggest that men with symptoms and a total testosterone below 8 nmol/L are likely to benefit from treatment. Levels between 8–12 nmol/L represent a zone where a careful assessment determines whether a treatment trial is appropriate. Free testosterone and SHBG must also be considered — total testosterone alone can be misleading.

  • Several things can explain this: raised SHBG reducing free (biologically active) testosterone; androgen receptor sensitivity differences related to CAG repeat length; or symptoms caused by something other than testosterone — such as depression, thyroid dysfunction, poor sleep, or psychological factors. A thorough clinical assessment is far more useful than repeating the same blood test.

  • Testosterone therapy is an amber-list drug in the UK, which means it is usually initiated by a specialist — many GPs are hesitant to prescribe it directly. NHS waiting times for endocrinology referrals are often lengthy, which is why many men seek private assessment. Private consultation allows faster access and thorough evaluation.

  • This is one of the most common presentations I see. It may mean the preparation or dose needs adjusting — but it may also mean that testosterone was never the primary cause of your symptoms. Sexual difficulties, fatigue, and mood problems are often multifactorial. I specialise in men who are on TRT but not improving, and can assess both the hormonal and psychosexual picture.

  • There is no single best form — the right preparation depends on your lifestyle, how your body responds to testosterone, your preference around injections, and your priorities around convenience versus dose flexibility. I discuss all options with patients before starting, and am happy to switch preparations if the first choice isn't working.

  • When appropriately prescribed and monitored, TRT is a safe and effective treatment for confirmed testosterone deficiency. Regular follow-up — including monitoring of haematocrit, PSA, and hormone levels — is an essential part of safe care. I provide follow-up appointments at 1, 3, 6, and 12 months in the first year, and at least annually thereafter.

  • My practice is at Central Health London, 23 Devonshire Place, Marylebone, London W1G 6JB — close to Harley Street in Central London. I also offer video consultations for patients across the UK and internationally.

  • Yes — I see men of all sexual orientations and have a particular interest in gay and bisexual men's health. As a gay man myself, I offer an open, non-judgmental space where you can speak frankly about whatever is going on.

Book an appointment with Dr Ben Davis

BOOK AN INITIAL CONSULTATION

Initial consultations are 60 minutes (£400) and cover a comprehensive assessment of your symptoms, history, and blood results. If you're not sure whether your concerns warrant a full appointment, you're welcome to email first: contact@drben.uk

I see patients in person at Central Health London, 23 Devonshire Place, Marylebone, London W1G 6JB, and offer video consultations for those outside London.