How much muscle gain will I get with Testogel is a common question among men prescribed testosterone replacement therapy (TRT) for hypogonadism. Testogel is a transdermal testosterone gel licensed in the UK to restore normal testosterone levels in men with confirmed deficiency, not for bodybuilding or performance enhancement. Whilst TRT can improve body composition, muscle gains are modest and gradual—typically 1.5–2.0 kg lean mass over 6–12 months when combined with resistance training. This article examines realistic expectations, clinical evidence, and safe use of Testogel under medical supervision, emphasising that treatment aims to restore normal physiology rather than create supraphysiological muscle growth.

What Is Testogel and How Does It Work?

Testogel is a transdermal testosterone replacement therapy (TRT) licensed in the UK for treating male hypogonadism—a condition where the body produces insufficient testosterone. It contains testosterone as the active ingredient, delivered through a clear gel applied daily to the skin.

Testogel is available in two main formulations in the UK:

• Testogel 50 mg/5 g (1%) gel in sachets: each 5 g sachet delivers 50 mg testosterone; applied to shoulders, upper arms, or abdomen

• Testogel 16.2 mg/g gel in pump dispenser: each 1.25 g pump actuation delivers 20.25 mg testosterone; applied to shoulders and upper arms

Usual starting doses range from 50 mg daily (one sachet or approximately two pump actuations), with titration based on blood testosterone levels and clinical response, up to a maximum of 81 mg daily for the pump formulation. Your doctor will determine the appropriate dose and formulation for your individual needs.

Once applied, testosterone is absorbed through the skin into the bloodstream, where it gradually restores physiological testosterone levels. Transdermal gels provide more stable testosterone concentrations than some short-acting injectable preparations, though individual absorption varies and long-acting injectables also offer steady hormone delivery.

Mechanism of action: Testosterone exerts its effects by binding to androgen receptors throughout the body, including in muscle tissue, bone, and the central nervous system. In skeletal muscle, testosterone promotes protein synthesis and inhibits protein breakdown, creating an anabolic environment that supports muscle maintenance and growth. It also influences satellite cell activation—specialised cells that contribute to muscle repair and hypertrophy.

Testogel is not licensed for performance enhancement, bodybuilding, or cosmetic muscle gain in individuals with normal testosterone levels. Its use is strictly indicated for men with confirmed hypogonadism, diagnosed through clinical symptoms and repeated early-morning blood tests showing low serum testosterone (typically total testosterone below 8 nmol/L on two separate occasions). Non-prescribed supply or use of testosterone is unlawful and carries significant health risks. Misuse of testosterone products outside medical supervision is not supported by UK regulatory authorities including the MHRA.

Important: Testosterone replacement therapy suppresses the body's own testosterone production and sperm production (spermatogenesis). If you are planning to father children, discuss this with your doctor before starting treatment, as alternative therapies or sperm cryopreservation may be appropriate.

Realistic Muscle Gain Expectations with Testogel

When prescribed appropriately for hypogonadism, Testogel aims to restore testosterone to normal physiological levels—not to create supraphysiological concentrations. Consequently, muscle gain expectations should be modest and realistic, particularly compared to anabolic steroid misuse.

Clinical studies in men with confirmed hypogonadism starting TRT typically report:

• Gradual increases in lean body mass over 6–12 months

• Modest reductions in fat mass, particularly visceral adipose tissue

• Improved muscle strength and physical function, especially in previously symptomatic individuals

• Variable improvements in exercise capacity, though evidence is modest and individual responses differ

However, the extent of muscle gain varies considerably between individuals. Men who were significantly hypogonadal before treatment (testosterone levels well below 8 nmol/L) may notice more pronounced improvements in body composition, whilst those with borderline testosterone levels may experience subtler changes. It is important to understand that Testogel restores normal physiology—it does not create an enhanced anabolic state beyond what is naturally achievable.

Typical lean mass changes reported in systematic reviews and meta-analyses range from approximately 1.5–2.0 kg over 6–12 months, though this includes all lean tissue (muscle, connective tissue, organ mass) rather than pure skeletal muscle. These gains are generally accompanied by modest improvements in strength and functional capacity, which may be more clinically meaningful than absolute mass changes. Fat mass reductions of approximately 1.5–2.5 kg over the same period have also been observed.

Patients should not expect dramatic bodybuilding-style transformations from medically supervised TRT. The primary goal of Testogel therapy is symptom relief (improved energy, mood, sexual function, and quality of life), with body composition changes being a secondary benefit rather than the primary therapeutic aim.

Factors That Influence Muscle Development on Testosterone Therapy

Multiple variables determine the extent of muscle development during Testogel therapy, making individual responses highly variable:

Baseline testosterone levels: Men with severely low testosterone (typically below 8 nmol/L) often experience more noticeable improvements in muscle mass compared to those with borderline deficiency. The degree of hormonal restoration correlates with potential anabolic response.

Age and treatment duration: Younger men generally demonstrate greater muscle responsiveness to testosterone therapy. Additionally, muscle mass changes occur gradually—most lean mass and strength gains are apparent within 6–12 months of consistent treatment, with ongoing benefits in those who maintain resistance training. Early discontinuation limits potential benefits.

Resistance training and physical activity: Testosterone creates a permissive environment for muscle growth, but exercise stimulus remains essential. Studies consistently show that TRT combined with structured resistance training produces significantly greater muscle gains than TRT alone. Without adequate mechanical loading through exercise, the anabolic potential of testosterone cannot be fully realised.

Nutritional status: Adequate protein intake and overall caloric sufficiency are crucial for muscle development. Protein requirements vary by individual circumstances; those engaging in regular resistance training may benefit from higher intakes, but patients with certain conditions (such as chronic kidney disease) require individualised dietary assessment. Discuss your nutritional needs with your healthcare team.

Adherence to therapy: Consistent daily application of Testogel is essential for maintaining stable testosterone levels. Irregular use results in fluctuating hormone concentrations that may compromise therapeutic benefits.

Concurrent medical conditions: Conditions such as diabetes, obesity, chronic kidney disease, or inflammatory disorders may blunt the anabolic response to testosterone therapy. Optimising management of comorbidities enhances treatment outcomes. Testosterone therapy requires caution in men with severe cardiac, hepatic, or renal disease, and may worsen obstructive sleep apnoea or cause fluid retention in susceptible individuals.

Genetic factors: Individual variation in androgen receptor sensitivity, muscle fibre type distribution, and baseline muscle mass potential all influence response to TRT.

Clinical Evidence: Muscle Mass Changes During TRT

Systematic reviews and meta-analyses of testosterone replacement therapy provide the most robust evidence regarding body composition changes. Multiple meta-analyses published in journals including the European Journal of Endocrinology and the Journal of Clinical Endocrinology & Metabolism have examined randomised controlled trials in hypogonadal men and found that TRT produces:

• Mean increase in lean body mass: approximately 1.5–2.0 kg over 6–12 months

• Mean decrease in fat mass: approximately 1.5–2.5 kg over the same period

• Modest improvements in muscle strength: particularly in lower limb strength measures, though effect sizes are variable

These changes are statistically significant but clinically modest, emphasising that TRT produces physiological rather than pharmacological effects when used appropriately at replacement doses.

The European Male Ageing Study (EMAS), a large observational cohort, demonstrated that testosterone levels correlate with muscle mass and strength in older men, but the relationship is complex and influenced by multiple factors including physical activity levels and overall health status.

NICE Clinical Knowledge Summaries (CKS) on testosterone deficiency acknowledge that TRT may improve body composition in hypogonadal men but emphasise that treatment decisions should be based primarily on symptom relief and confirmed biochemical deficiency rather than body composition goals. NICE CKS and the British Society for Sexual Medicine (BSSM) recommend:

• Confirming diagnosis with two early-morning total testosterone measurements (typically below 8 nmol/L), with consideration of sex hormone-binding globulin (SHBG), calculated free testosterone, luteinising hormone (LH), follicle-stimulating hormone (FSH), and prolactin where appropriate

• Regular monitoring of testosterone levels, full blood count (including haematocrit), and prostate parameters

• Realistic patient counselling regarding treatment expectations

Studies comparing different TRT formulations (gels, injections, patches) show similar body composition outcomes when physiological testosterone levels are adequately achieved, though injectable preparations may carry a higher risk of elevated haematocrit (red blood cell concentration). The route of administration is less important than achieving stable physiological testosterone concentrations and maintaining treatment adherence.

There is no evidence that Testogel use at therapeutic replacement doses produces the dramatic muscle gains associated with anabolic steroid misuse, which typically involves doses 10–100 times higher than replacement therapy and carries serious health risks.

Safe Use of Testogel Under Medical Supervision

Testogel should be initiated by a clinician experienced in the management of testosterone deficiency, typically an endocrinologist or urologist. Ongoing monitoring may be shared with your GP according to local care pathways. Self-medication or use for performance enhancement is dangerous and unlawful.

Application technique varies by formulation:

• Testogel 50 mg/5 g sachets (1%): Apply to clean, dry, intact skin on shoulders, upper arms, or abdomen (not genital area). Allow to dry for 3–5 minutes before dressing.

• Testogel 16.2 mg/g pump: Apply to clean, dry, intact skin on shoulders and upper arms only. Allow to dry before dressing.

For both formulations:

• Wash hands thoroughly with soap and water immediately after application

• Avoid skin-to-skin contact with others (especially women and children) until the gel has dried and the application site is covered with clothing, or for at least 6 hours

• Showering or swimming should be delayed for at least 6 hours after application to ensure adequate absorption

• If direct skin contact occurs, the other person should wash the contact area with soap and water as soon as possible

Refer to the patient information leaflet supplied with your specific Testogel product for detailed instructions.

Monitoring requirements: Regular blood tests and clinical review are essential. Typical monitoring includes:

• Testosterone levels: checked after initiation and dose adjustments (timing depends on formulation; your doctor will advise), then every 3–6 months once stable

• Full blood count (FBC) including haematocrit: baseline, at 3–6 months, then annually. Elevated haematocrit (red blood cell concentration) is common; if haematocrit exceeds 54%, your doctor may reduce the dose or temporarily stop treatment

• Prostate assessment: baseline prostate-specific antigen (PSA) and digital rectal examination (DRE) where clinically indicated, particularly in men aged 50 and over or those aged 45 and over with risk factors for prostate cancer; ongoing monitoring as advised by your specialist

• Other tests as clinically indicated: liver and kidney function, lipid profile, bone density, and glucose/HbA1c in men with diabetes or metabolic syndrome

Common adverse effects include:

• Skin reactions at application site (redness, irritation, itching)

• Acne or oily skin

• Increased haematocrit (red blood cell count)

• Mood changes

• Breast tenderness or enlargement (gynaecomastia)

• Ankle swelling (oedema)

• Worsening of obstructive sleep apnoea symptoms

Important drug interactions: Testosterone may interact with:

• Anticoagulants (e.g., warfarin): testosterone can enhance anticoagulant effects; INR monitoring and dose adjustment may be required

• Antidiabetic medicines (insulin, oral hypoglycaemics): testosterone may reduce blood glucose; monitor glucose levels and adjust antidiabetic therapy as needed

• Corticosteroids or ACTH: combined use may increase the risk of fluid retention and oedema

Inform your doctor and pharmacist of all medicines you are taking, including over-the-counter and herbal products.

When to contact your GP or specialist urgently:

• Signs of blood clots (leg swelling, pain, chest pain, breathlessness)

• Prolonged or painful erections lasting more than 4 hours (priapism)

• Significant mood changes, depression, or aggression

• Symptoms of heart failure (ankle swelling, breathlessness, rapid weight gain)

• Yellowing of skin or eyes (jaundice)

• Severe skin reactions

Contraindications: Testogel must not be used in men with:

• Prostate cancer or male breast cancer (current or suspected)

Testogel requires caution and specialist assessment in men with:

• Severe heart, liver, or kidney disease

• Obstructive sleep apnoea

• Conditions predisposing to fluid retention or oedema

• History of, or risk factors for, venous thromboembolism

Testogel is not appropriate for women (except in very specific specialist scenarios under expert supervision) or children. Patients should never share medication or adjust doses without medical guidance.

Fertility: Testosterone replacement therapy suppresses sperm production and can cause infertility. If you are planning to father children, discuss this with your doctor before starting treatment. Alternative treatments or sperm cryopreservation may be options.

Reporting side effects: If you experience any side effects, talk to your doctor or pharmacist. You can also report suspected side effects directly via the MHRA Yellow Card scheme at www.mhra.gov.uk/yellowcard or search for "MHRA Yellow Card" in the Google Play or Apple App Store. Reporting helps provide information on the safety of medicines.

Frequently Asked Questions