Many men experiencing persistent fatigue, low mood, reduced libido, and declining physical vitality discover that testosterone deficiency is the underlying cause. When properly diagnosed and treated, testosterone replacement therapy can lead to profound improvements in energy, wellbeing, and quality of life. However, accessing treatment in the UK requires meeting specific clinical criteria, including blood tests confirming consistently low testosterone levels. This article explores how testosterone treatment works, what realistic changes to expect, NHS eligibility requirements, and the importance of ongoing monitoring to ensure safe, effective therapy tailored to individual needs.

Understanding Low Testosterone and Its Impact on Daily Life

Testosterone is the primary male sex hormone responsible for maintaining muscle mass, bone density, libido, mood regulation, and energy levels. When testosterone levels fall below the normal range—a condition known as hypogonadism or testosterone deficiency—the effects can be profound and far-reaching.

Common symptoms of low testosterone include:

• Persistent fatigue and reduced energy levels

• Decreased libido and erectile dysfunction

• Loss of muscle mass and increased body fat

• Mood changes, including depression, irritability, and poor concentration

• Reduced bone density, increasing fracture risk

• Sleep disturbances and reduced quality of life

These symptoms often develop gradually, making them easy to dismiss as normal ageing or stress. However, when testosterone deficiency is clinically confirmed, the impact on daily functioning can be substantial. Men may find themselves withdrawing from social activities, experiencing relationship difficulties, and struggling with work performance. The psychological burden of unexplained fatigue and mood changes can be particularly distressing.

It is important to recognise that low testosterone is a medical condition requiring proper diagnosis. Symptoms alone are not sufficient for diagnosis, as they overlap with numerous other conditions including thyroid disorders, depression, sleep apnoea, and diabetes. UK clinical guidance (NICE Clinical Knowledge Summary on male hypogonadism) emphasises that testosterone deficiency must be confirmed through blood tests showing consistently low testosterone levels, measured on two separate early-morning occasions, preferably while fasting and not during acute illness. A comprehensive assessment considers both biochemical evidence and clinical symptoms before treatment is considered.

Important warning signs requiring urgent medical attention include:

• New severe headaches

• Visual disturbances

• Unusual breast discharge (galactorrhoea) These may indicate pituitary problems requiring immediate specialist assessment.

How Testosterone Replacement Therapy Works in the UK

Testosterone replacement therapy (TRT) aims to restore testosterone levels to the normal physiological range, thereby alleviating symptoms of deficiency. In the UK, TRT is available through the NHS and private healthcare providers, but it must be prescribed by a qualified medical professional following appropriate investigation.

Mechanism of action: Exogenous testosterone supplementation works by directly increasing circulating testosterone levels in the bloodstream. Once absorbed, testosterone binds to androgen receptors throughout the body, influencing protein synthesis, red blood cell production, bone metabolism, and numerous other physiological processes. The therapy does not cure the underlying cause of low testosterone but provides symptomatic relief by maintaining adequate hormone levels.

Available formulations in the UK include:

• Transdermal gels: Applied daily to the skin (e.g., Testogel, Tostran, Testavan), providing steady hormone levels

• Long-acting intramuscular injections: Testosterone undecanoate (Nebido) given initially, then at 6 weeks, followed by every 10–14 weeks thereafter

• Short-acting intramuscular injections: Testosterone enantate or mixed esters (e.g., Sustanon) given every 2–4 weeks

• Transdermal patches: Limited availability in the UK and less commonly used due to skin irritation

The choice of formulation depends on patient preference, lifestyle considerations, cost, and clinical factors. Gels offer convenience and stable levels but require daily application and precautions to prevent transfer to others. When using gels, it's essential to apply to clean, dry skin, wash hands thoroughly afterwards, allow the gel to dry completely, and cover the application site with clothing to prevent transfer to women and children.

Long-acting injections reduce administration frequency but may cause fluctuating hormone levels. Your endocrinologist or specialist will discuss the most appropriate option based on your individual circumstances, ensuring the treatment aligns with UK-approved indications as outlined in the MHRA product licences and BNF guidance.

Real Changes: What to Expect from Testosterone Treatment

When testosterone replacement therapy is appropriately prescribed for confirmed deficiency, many men experience significant improvements in their symptoms. However, it is essential to have realistic expectations, as the timeline and extent of benefits vary between individuals.

Early changes (within 3–6 weeks):

Most men notice improvements in mood, energy levels, and sense of wellbeing relatively quickly. Libido often begins to increase within the first month, though erectile function may take longer to improve. Some men report better sleep quality and reduced irritability during this initial period.

Intermediate changes (3–6 months):

Physical changes become more apparent during this phase. Muscle mass and strength typically increase, particularly when combined with resistance exercise. Body composition may shift, with reduced fat mass, especially around the abdomen. Bone mineral density begins to improve, though this continues over years. Erectile function generally shows progressive improvement during this timeframe, though some men may require additional treatments such as PDE5 inhibitors even with normalised testosterone levels.

Long-term benefits (6–12 months and beyond):

Maximum benefits are usually achieved after 6–12 months of consistent treatment. Quality of life improvements often plateau at this stage, with sustained energy, mood stability, and sexual function. Bone density continues to increase over several years, reducing fracture risk.

Important considerations:

Not all symptoms respond equally to treatment. If low testosterone is not the primary cause of symptoms, TRT will not provide benefit. Additionally, there is no official link between testosterone therapy and dramatic personality changes or guaranteed improvements in all life domains. Response varies based on baseline testosterone levels, age, overall health, and adherence to treatment.

Fertility warning: Testosterone therapy suppresses sperm production and is not suitable for men wishing to father children. If fertility is desired, alternative treatments should be discussed with a specialist. Regular monitoring ensures therapy remains effective and safe, with dose adjustments made as needed.

NHS Eligibility and Getting Assessed for Testosterone Therapy

Accessing testosterone replacement therapy through the NHS requires meeting specific clinical criteria. The process is designed to ensure that treatment is only provided to men with genuine testosterone deficiency, as inappropriate use carries health risks.

Initial assessment with your GP:

If you are experiencing symptoms suggestive of low testosterone, the first step is consulting your GP. They will take a detailed medical history, including symptom duration and severity, and perform a physical examination. Your GP will also consider alternative explanations for your symptoms, such as depression, thyroid disease, or sleep disorders, and address reversible causes including obesity, sleep apnoea, opioid or steroid medication use, and excessive alcohol consumption.

Diagnostic blood tests:

If testosterone deficiency is suspected, your GP will arrange blood tests to measure total testosterone levels. According to UK clinical practice (NICE CKS), this should be performed on two separate occasions, in the early morning (7am–11am) when testosterone levels are naturally highest, preferably while fasting and not during acute illness.

A diagnosis typically follows these guidelines:

• Total testosterone below 8 nmol/L with symptoms usually warrants treatment

• Levels between 8–12 nmol/L are considered borderline, requiring assessment of symptoms, measurement of sex hormone-binding globulin (SHBG) to calculate free testosterone, and clinical judgement

Additional tests may include:

• Luteinising hormone (LH) and follicle-stimulating hormone (FSH) to determine if the problem originates in the testes or pituitary gland

• Prolactin levels to exclude pituitary tumours

• Full blood count, liver function, and lipid profile

• PSA (prostate-specific antigen) in men over 40

Referral to specialist services:

If blood tests confirm low testosterone, your GP will typically refer you to an endocrinologist or specialist in male reproductive health. Urgent referral is needed if there are signs of pituitary disease (low/normal LH with low testosterone, raised prolactin, or visual/neurological symptoms). The specialist will review your results, exclude secondary causes, and determine whether TRT is appropriate. NHS waiting times for endocrinology appointments vary by region but can extend to several months. Private assessment is an alternative for those seeking faster access, though ongoing NHS prescriptions depend on local shared-care agreements and formulary policies, and cannot be guaranteed.

Managing Treatment: Monitoring, Side Effects and Long-Term Care

Once testosterone replacement therapy is initiated, ongoing monitoring is essential to ensure efficacy, safety, and early detection of potential complications. UK clinical guidance recommends structured follow-up protocols.

Regular monitoring schedule:

Baseline assessments should include haematocrit, PSA (in men over 40), and consideration of prostate examination according to age and risk factors. During the first year, you will typically have blood tests at 3, 6, and 12 months to assess testosterone levels, full blood count (particularly haematocrit), PSA, and liver function. After stabilisation, annual monitoring is usually sufficient. Your clinician will also assess symptom improvement and treatment satisfaction at each visit.

Common side effects and management:

• Polycythaemia (increased red blood cell count): Testosterone stimulates red blood cell production, which can increase blood viscosity and thrombotic risk. If haematocrit exceeds 0.54, treatment should be temporarily stopped or the dose reduced, and causes evaluated.

• Skin reactions: Gels and patches may cause local irritation. Rotating application sites or switching formulations can help.

• Acne and oily skin: Increased sebum production is common but usually mild and manageable with appropriate skincare.

• Fluid retention: Some men experience mild ankle swelling, which typically resolves with time.

• Mood changes: While TRT generally improves mood, some men report increased irritability, particularly with injection formulations that cause fluctuating levels.

• Gynaecomastia: Breast tenderness or enlargement may occur and should be reported to your doctor.

• Worsening urinary symptoms: Men with pre-existing prostate enlargement may experience increased lower urinary tract symptoms.

Important safety considerations:

Testosterone therapy is contraindicated in men with prostate or breast cancer. It should be used with caution in men with untreated severe sleep apnoea or significant heart failure. There is ongoing debate about cardiovascular risks, though current evidence does not establish a definitive link when therapy is appropriately prescribed and monitored.

Prostate monitoring is important: if PSA rises significantly or exceeds age-specific ranges before or during treatment, referral to urology is recommended.

When to contact your GP:

Seek medical advice if you experience chest pain, severe leg swelling, sudden shortness of breath, or urinary symptoms such as difficulty passing urine. These may indicate serious complications requiring urgent evaluation. Report any suspected side effects to your healthcare professional or directly to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk). Long-term success with TRT requires partnership between patient and healthcare provider, with regular review ensuring treatment remains beneficial and safe.

Frequently Asked Questions