Testogel is a prescription testosterone replacement therapy licensed in the UK for treating male hypogonadism—a condition where the body produces insufficient testosterone. Whilst restoring testosterone to normal levels in men with confirmed deficiency may help reverse muscle loss associated with low testosterone, Testogel is not licensed or intended for muscle building in healthy individuals. Using testosterone products without medical supervision carries significant health and legal risks. This article examines the evidence on Testogel and muscle development, explains when testosterone therapy is appropriate, and outlines safe, evidence-based alternatives for building muscle naturally.

What Is Testogel and How Does It Work?

Testogel is a prescription-only testosterone replacement therapy (TRT) available in the UK, licensed by the Medicines and Healthcare products Regulatory Agency (MHRA). It contains testosterone as the active ingredient, formulated as a clear, colourless gel applied topically to the skin. The gel is designed to deliver a controlled dose of testosterone transdermally, allowing the hormone to be absorbed through the skin and into the bloodstream.

The primary indication for Testogel is the treatment of male hypogonadism, a clinical condition characterised by insufficient testosterone production by the testes. Symptoms of hypogonadism may include reduced libido, erectile dysfunction, fatigue, loss of muscle mass, increased body fat, mood disturbances, and decreased bone density. Testogel works by supplementing endogenous testosterone levels, thereby alleviating these symptoms and restoring physiological hormone balance.

Application and safety: The approved application sites depend on the specific formulation. For Testogel 16.2 mg/g, the electronic Medicines Compendium (emc) Summary of Product Characteristics (SmPC) recommends application to the shoulders and upper arms only. After application, allow the gel to dry for a few minutes, then cover the area with clothing. Wash your hands thoroughly with soap and water immediately after applying the gel. To prevent transfer of testosterone to others—particularly women and children—avoid skin-to-skin contact with the application site until it is dry and covered. Wash the application area with soap and water before any close physical contact. The gel contains alcohol and is flammable; avoid flames, smoking, or sources of ignition until the gel has dried. Do not apply to the genitals or broken skin.

Mechanism of action: Once absorbed, testosterone binds to androgen receptors in various tissues throughout the body, including muscle, bone, and the central nervous system. This binding initiates a cascade of cellular processes that influence protein synthesis, nitrogen retention, and metabolic function. In muscle tissue specifically, testosterone promotes anabolic processes that support muscle protein synthesis and may help maintain lean body mass in men with clinically low testosterone levels.

Diagnosis and prescribing: Testogel should only be prescribed following confirmed biochemical hypogonadism with appropriate clinical symptoms. Diagnosis requires two early-morning fasting serum total testosterone measurements (taken on separate occasions) showing levels below the normal reference range, alongside compatible symptoms and signs. Additional tests—such as sex hormone-binding globulin (SHBG), calculated free testosterone, luteinising hormone (LH), follicle-stimulating hormone (FSH), and prolactin—may be indicated to assess the hypothalamic-pituitary-gonadal axis and exclude secondary causes.

It is crucial to understand that Testogel is not licensed or intended for muscle building in healthy individuals. The MHRA and the National Institute for Health and Care Excellence (NICE) emphasise that testosterone replacement should only be prescribed for confirmed hypogonadism. Misuse of testosterone products outside of legitimate medical indications carries significant health risks.

References: emc SmPC: Testogel 16.2 mg/g (testosterone); NICE Clinical Knowledge Summaries (CKS): Testosterone deficiency in men; NHS Medicines A–Z: Testosterone (topical gel).

Does Testogel Build Muscle Mass?

The question of whether Testogel builds muscle is nuanced and depends critically on the clinical context. In men with diagnosed hypogonadism and genuinely low testosterone levels, restoring testosterone to normal physiological ranges can help reverse muscle loss (sarcopenia) associated with the deficiency. Clinical studies and systematic reviews have demonstrated that testosterone replacement therapy may improve lean body mass, muscle strength, and physical function in this specific patient population when combined with appropriate resistance exercise.

However, Testogel is not indicated and offers no proven benefit for muscle building in men with normal testosterone levels (eugonadal men). The body tightly regulates testosterone production through a negative feedback loop involving the hypothalamus and pituitary gland. When exogenous testosterone is introduced in individuals with normal endogenous production, the body responds by reducing its own testosterone synthesis, leading to suppression of spermatogenesis (reduced or absent sperm production), testicular atrophy, and potential long-term fertility impairment.

Furthermore, any muscle gains observed with supraphysiological testosterone use (doses exceeding normal ranges) come with substantial health risks, including cardiovascular complications, haematological abnormalities, psychiatric effects, and endocrine disruption. The anabolic effects seen in bodybuilding contexts typically involve doses far exceeding therapeutic ranges and often include multiple androgenic agents—a practice associated with serious adverse outcomes and no legitimate medical indication.

Treatment targets and monitoring: NICE CKS and the British Society for Sexual Medicine (BSSM) guideline on adult testosterone deficiency specify that testosterone therapy should aim for serum testosterone levels in the mid-normal range, using the local laboratory's reference range. For testosterone gels, serum testosterone should be measured at steady state (after at least one week of treatment) and timed appropriately—typically 2–4 hours after gel application—as levels fluctuate during the day. Treatment should be individualised, with regular monitoring to prevent supraphysiological levels and to assess clinical response.

Key clinical point: Testogel is formulated to restore deficient testosterone levels to the normal physiological range, not to elevate them beyond this. Using Testogel solely for muscle enhancement in the absence of hypogonadism is inappropriate, ineffective for sustainable gains, and potentially dangerous. Individuals seeking muscle development should focus on evidence-based training and nutrition strategies rather than hormonal manipulation.

References: NICE CKS: Testosterone deficiency in men; BSSM guideline on adult testosterone deficiency; systematic reviews/meta-analyses on TRT effects on lean body mass and strength in hypogonadal men.

Risks of Using Testogel Without Medical Supervision

Using Testogel without proper medical supervision and a legitimate prescription carries significant health risks and legal consequences. Testosterone is a controlled substance under UK law, classified as a Class C drug under the Misuse of Drugs Act 1971. It is illegal to supply, produce, import, or export testosterone without authority. Simple possession of anabolic steroids for personal use is not a criminal offence in the UK; however, obtaining prescription-only medicines without a valid prescription, and importing testosterone (e.g., by post or courier), are unlawful and pose serious health and legal risks. Supplying or distributing testosterone products can result in criminal prosecution.

From a medical perspective, unsupervised testosterone use can lead to numerous adverse effects, including:

• Cardiovascular and thromboembolic risks: Evidence on cardiovascular risk with testosterone therapy is mixed and remains under review. However, the MHRA and European Medicines Agency (EMA) have issued warnings regarding an increased risk of venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism. Testosterone therapy should be used with caution in men with established cardiovascular disease, and individual cardiovascular risk should be assessed before and during treatment. Regular monitoring is essential.

• Haematological effects: Testosterone stimulates erythropoiesis and can cause polycythaemia (elevated red blood cell count). The emc SmPC advises monitoring haematocrit and haemoglobin regularly. If haematocrit exceeds 0.54 (54%), treatment should be paused or the dose reduced until levels normalise. Polycythaemia increases the risk of thrombotic events.

• Endocrine disruption and fertility: Testosterone replacement therapy suppresses the hypothalamic-pituitary-gonadal axis, leading to reduced or absent sperm production (oligospermia or azoospermia), testicular atrophy, and potential long-term infertility. TRT is contraindicated in men who are actively trying to conceive; alternative treatments to preserve or restore fertility should be discussed with a specialist. Gynaecomastia (breast tissue development) may occur due to aromatisation of testosterone to oestradiol.

• Hepatic effects: Serious hepatotoxicity is primarily associated with oral 17-alpha-alkylated androgens, not transdermal testosterone. Transdermal testosterone has a low hepatic risk profile, though liver function tests may be monitored if clinically indicated.

• Psychiatric effects: Mood disturbances, aggression, irritability, and in some cases, manic or psychotic episodes. There is also concern regarding dependency and abuse potential.

• Dermatological reactions: Acne, oily skin, male pattern baldness, and local skin irritation at application sites.

• Prostate and urological concerns: Testosterone does not cause prostate cancer, but it may accelerate pre-existing disease. Benign prostatic hyperplasia may worsen. Prostate-specific antigen (PSA) and digital rectal examination (DRE) should be performed before treatment and monitored regularly in men aged over 40 or those at higher risk. Testosterone may also worsen obstructive sleep apnoea; evaluate and manage if symptoms develop.

• Secondary exposure: A critical safety concern with testosterone gels is the risk of unintentional transfer to women and children through skin-to-skin contact. This can cause virilisation in women and children (e.g., genital changes, premature sexual development). To prevent transfer: wash hands immediately after application; allow the gel to dry fully; cover the application site with clothing; wash the application area with soap and water before close physical contact.

• Flammability: The gel contains alcohol and is flammable. Avoid open flames, smoking, or sources of ignition until the gel has completely dried on the skin.

Monitoring requirements: Legitimate testosterone therapy requires regular blood tests to assess serum testosterone levels (timed appropriately for gels), haematocrit and haemoglobin, PSA (in men aged ≥40 years or at risk), and—if clinically indicated—liver function and lipid profile. Symptoms and signs should be reviewed regularly, and treatment adjusted accordingly. Without medical supervision, these potentially serious complications may go undetected until significant harm has occurred.

Reporting side effects: If you experience any side effects while using Testogel, report them via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or via the Yellow Card app. Reporting helps improve the safety of medicines for everyone.

If you are considering testosterone therapy, consult your GP for proper evaluation and, if appropriate, referral to an endocrinologist or specialist in sexual medicine.

References: GOV.UK: Drug penalties – anabolic steroids; MHRA Drug Safety Update: Testosterone – risk of venous thromboembolism and monitoring; emc SmPC: Testogel 16.2 mg/g – contraindications, transfer risk, monitoring (haematocrit threshold); NICE CKS: Testosterone deficiency – monitoring and contraindications.

Safe Alternatives for Building Muscle Naturally

For individuals seeking to build muscle mass without resorting to hormonal interventions, evidence-based natural approaches offer safe and effective alternatives. These methods are supported by robust scientific evidence and align with guidance from organisations such as the British Association of Sport and Exercise Sciences (BASES) and the NHS.

Progressive resistance training forms the cornerstone of muscle development. A structured programme incorporating compound exercises (squats, deadlifts, bench press, rows) performed 3–5 times weekly with progressive overload—gradually increasing weight, repetitions, or training volume—stimulates muscle protein synthesis and hypertrophy. The NHS recommends strength training at least twice weekly for general health; more frequent training may be required for significant muscle gains.

Optimised nutrition is equally critical:

• Protein intake: A target of 1.6–2.2 grams of protein per kilogram of body weight daily, distributed across multiple meals, is commonly recommended for individuals engaged in regular resistance training. High-quality protein sources include lean meats, fish, eggs, dairy products, legumes, and soya products. Protein and energy requirements vary by individual goals, age, and health status. If you have kidney disease, diabetes, or other medical conditions, seek advice from your GP or a registered dietitian before significantly increasing protein intake.

• Energy balance: A modest caloric surplus (approximately 200–500 kcal above maintenance) supports muscle growth whilst minimising excessive fat gain.

• Micronutrients: Ensure adequate intake of vitamins D and B12, iron, zinc, and magnesium, which support muscle function and recovery.

Recovery and sleep: Muscle growth occurs during recovery periods. Aim for 7–9 hours of quality sleep nightly, as growth hormone secretion and muscle protein synthesis are optimised during deep sleep stages.

Lifestyle factors: Manage stress through evidence-based techniques such as mindfulness or cognitive behavioural approaches, as chronic stress elevates cortisol, which can impair muscle growth. Avoid excessive alcohol consumption, which interferes with protein synthesis and recovery.

When to seek medical advice: If you experience unexplained difficulty building muscle despite consistent training and nutrition, persistent fatigue, reduced libido, erectile dysfunction, or other symptoms suggestive of hypogonadism, consult your GP. They can arrange appropriate investigations, including two early-morning fasting serum testosterone measurements (taken on separate occasions), thyroid function tests, full blood count (to assess for anaemia), and evaluation for other underlying conditions. Do not self-medicate with prescription-only products. If fertility is a concern or goal, discuss this with your doctor before considering any hormonal treatment, as testosterone replacement therapy suppresses sperm production and is not appropriate for men trying to conceive. Legitimate medical concerns should be addressed through proper clinical channels.

References: NHS Physical activity guidelines – strength training recommendations; British Association of Sport and Exercise Sciences (BASES) position statements on resistance training and nutrition; NICE CKS: Testosterone deficiency in men.

Frequently Asked Questions