Testogel is a testosterone replacement therapy licensed in the UK for treating male hypogonadism, not for weight loss or bodybuilding. Whilst testosterone influences body composition by supporting muscle development and affecting fat metabolism, the medication produces modest, gradual changes when used at therapeutic doses. Men with testosterone deficiency may experience some reduction in body fat—particularly visceral fat—alongside small increases in lean muscle mass over 6–12 months of treatment. However, achieving extremely low body fat levels requires intensive training, strict dietary control, and genetic factors independent of testosterone replacement. This article explains how Testogel affects body composition, safe treatment goals, and essential monitoring requirements under UK clinical guidance.

What Is Testogel and How Does It Affect Body Composition?

Testogel is a transdermal testosterone replacement therapy (TRT) licensed in the UK for treating male hypogonadism—a condition where the testes produce insufficient testosterone. Available as a gel applied once daily to the skin, Testogel delivers bioidentical testosterone that is absorbed through the dermal layers into the bloodstream. The medication is regulated by the MHRA and prescribed when blood tests confirm low testosterone levels alongside clinical symptoms such as reduced libido, fatigue, mood disturbances, and changes in body composition.

Application sites vary by formulation: Testogel 16.2 mg/g (pump) is licensed for application to the shoulders and/or upper arms only. Some 1% sachet formulations may permit application to the abdomen—always follow the instructions in your patient information leaflet. After application, allow the gel to dry fully, wash your hands thoroughly, and cover the area with clothing to prevent accidental transfer to others (especially women and children). Avoid washing or showering the application site for the period specified in your product leaflet (typically several hours).

Diagnosis of hypogonadism requires at least two separate early-morning blood tests showing low testosterone, alongside symptoms. Your GP or endocrinologist will also check luteinising hormone (LH), follicle-stimulating hormone (FSH), and prolactin to identify the underlying cause and rule out secondary conditions.

Testosterone plays a fundamental role in regulating body composition. It promotes protein synthesis in skeletal muscle, supporting lean muscle mass development and maintenance. Testosterone also influences fat metabolism by modulating enzyme activity in fat cells and affecting how the body stores and breaks down fat. Men with hypogonadism often experience increased abdominal fat and reduced muscle mass—changes that may be partially reversed with appropriate testosterone replacement.

When Testogel restores testosterone to normal physiological levels, patients may observe gradual improvements in body composition over several months. Research suggests that TRT can produce modest reductions in body fat and small increases in lean body mass, though results vary considerably between individuals. These changes depend on baseline testosterone levels, treatment adherence, lifestyle factors (particularly diet and exercise), and concurrent health conditions. It is essential to understand that Testogel is licensed to treat testosterone deficiency, not as a weight-loss medication or performance-enhancing substance, and produces modest body composition changes within a therapeutic context.

How Testosterone Replacement Therapy Influences Body Fat

Testosterone influences adipose (fat) tissue through several mechanisms. At the cellular level, testosterone and its metabolite dihydrotestosterone (DHT) bind to androgen receptors in fat cells, affecting their metabolic activity. This hormonal signalling may reduce fat storage and increase fat breakdown. Additionally, testosterone supports lean muscle mass, and because muscle tissue is metabolically more active than fat, this can modestly increase daily energy expenditure.

Research indicates that testosterone replacement may preferentially reduce visceral adipose tissue—the metabolically harmful fat surrounding internal organs—rather than subcutaneous fat. This is clinically significant because visceral fat is associated with increased risk of cardiovascular disease, type 2 diabetes, and metabolic syndrome. Studies show that men receiving TRT may experience reductions in waist circumference and improvements in some metabolic markers, though effects are variable and modest on average.

The body composition effects of Testogel are gradual and modest when used at licensed therapeutic doses. Changes typically occur over 6–12 months of treatment, with most improvement in the first year. These effects plateau once testosterone levels stabilise within the normal physiological range for your laboratory (typically mid-normal range, often around 12–15 nmol/L or higher, but this varies). Importantly, higher doses do not produce proportionally greater fat loss and instead increase the risk of serious adverse effects including excessive red blood cell production (polycythaemia), cardiovascular events, suppression of natural testosterone production, and infertility.

Testogel addresses only one component of body composition. Combining TRT with a balanced diet and regular exercise—particularly resistance training—produces better outcomes than medication alone. Patients should work with their healthcare team to set realistic, health-focused goals aligned with their overall medical management plan.

Safe and Realistic Body Composition Goals on Testogel

When considering body composition during Testogel treatment, it is essential to distinguish between therapeutic outcomes and potentially harmful goals. In the UK, healthy body composition is typically assessed using body mass index (BMI) and waist circumference rather than body fat percentage. A healthy waist circumference is generally below 94 cm for men of white European origin (lower thresholds apply for some ethnic groups). Your GP can advise on appropriate targets for your individual circumstances.

Testogel, when used appropriately for hypogonadism, may help patients achieve healthier body composition if testosterone deficiency has contributed to increased abdominal fat. However, the medication alone will not produce extremely low body fat levels. Achieving very low body fat (such as that seen in competitive athletes) requires intensive training, strict dietary control, and genetic factors—elements independent of testosterone replacement. Moreover, excessively low body fat is associated with adverse health consequences including hormonal disruption, immune dysfunction, reduced bone density, and psychological disturbances.

The MHRA and NICE emphasise that Testogel should be prescribed to restore testosterone to normal physiological levels, not to achieve levels above the normal range. Target testosterone levels during treatment are typically mid-normal for your local laboratory reference range, measured as pre-dose morning levels after at least 14 days on a stable dose. Attempting to achieve extremely low body fat by using excessive doses of Testogel or combining it with other substances constitutes misuse and carries serious health risks.

Important: TRT suppresses sperm production and may impair fertility. If you are planning to have children, discuss this with your doctor before starting treatment, as alternative approaches may be more appropriate.

Any desire to achieve body fat levels significantly below healthy ranges should prompt discussion with your GP about underlying motivations and potential body image concerns. Testogel is not licensed or appropriate for weight loss, bodybuilding, or athletic performance enhancement.

Factors That Influence Body Composition Changes with Testogel

The degree of body composition change experienced during Testogel treatment varies substantially between individuals due to multiple interacting factors. Baseline testosterone levels are a significant determinant—men with more severe testosterone deficiency typically experience more noticeable improvements in body composition compared to those with borderline levels. The greatest benefits occur when correcting significant hormonal deficits rather than making small adjustments within the normal range.

Lifestyle factors profoundly influence outcomes. Testosterone replacement enhances the body's capacity to build muscle and metabolise fat, but these effects are substantially amplified by appropriate nutrition and exercise. Resistance training, in particular, works synergistically with testosterone to promote muscle development and increase metabolic rate. Conversely, a sedentary lifestyle and excessive caloric intake will limit improvements regardless of testosterone levels. Clinical evidence consistently demonstrates that patients who combine TRT with structured exercise and dietary modification achieve superior body composition outcomes compared to those receiving medication alone.

Additional factors include:

• Age: Older men may experience slower or less pronounced changes

• Concurrent medical conditions: Diabetes, metabolic syndrome, and thyroid disorders can affect body composition independently of testosterone status

• Medication adherence: Inconsistent application of Testogel results in fluctuating testosterone levels and suboptimal outcomes

• Genetic factors: Individual variation affects how tissues respond to testosterone

• Sleep quality: Poor sleep disrupts hormonal regulation and impairs body composition changes; untreated sleep apnoea may worsen on TRT

It is important to recognise that Testogel addresses only one component of body composition regulation. Patients should receive support for comprehensive lifestyle modification alongside medical treatment to achieve the best outcomes.

Monitoring and Safety During Testosterone Treatment

Appropriate monitoring during Testogel therapy is essential for ensuring both efficacy and safety. NICE and UK specialist guidance recommend that men receiving testosterone replacement undergo regular clinical and biochemical assessment. Typical monitoring includes review at 3 months and 6 months after starting treatment or changing dose, then at least annually once stable therapeutic levels are achieved.

Blood tests should include:

• Testosterone levels: measured as pre-dose morning levels (before applying that day's gel) after at least 14 days on a stable dose; target is mid-normal range for your local laboratory

• Full blood count: to monitor haematocrit (red blood cell concentration); treatment should be paused or adjusted if haematocrit exceeds 0.54, and further investigation arranged

• Prostate-specific antigen (PSA) and digital rectal examination: in men over 50 years (or over 45 with risk factors), as clinically indicated

• Other tests as appropriate: blood pressure, glucose, and lipids may be checked depending on your individual risk factors

Body composition assessment should form part of routine clinical evaluation using practical measures:

• Body mass index (BMI) and waist circumference at each review

• Clinical assessment of muscle mass and fat distribution

• Patient-reported changes in physical function and exercise capacity

Patients should understand that body composition changes occur gradually over months, not weeks. Unrealistic expectations about rapid fat loss may indicate misunderstanding of TRT's therapeutic purpose.

When to contact your GP:

• Unexplained or rapid weight change

• Signs of excessive testosterone: severe acne, aggressive behaviour, sleep disturbance

• Symptoms suggesting high red blood cell count: persistent headaches, visual disturbances, flushed appearance

• Cardiovascular symptoms: chest pain, breathlessness, leg swelling

• Mood changes, depression, or anxiety

• Urinary symptoms: difficulty passing urine, increased frequency, weak stream

• Worsening snoring or daytime sleepiness (possible sleep apnoea)

• Skin reactions at the application site

Important safety reminders:

• Wash your hands thoroughly after applying Testogel

• Allow the gel to dry completely and cover the area with clothing

• Avoid skin-to-skin contact with others (especially women and children) until after washing the application site

• Follow the recommended interval before showering or bathing (check your patient information leaflet)

• TRT suppresses sperm production; discuss fertility plans with your doctor

• Report any suspected side effects via the MHRA Yellow Card scheme (search 'Yellow Card' online or ask your pharmacist)

Regular monitoring ensures that Testogel therapy remains safe, effective, and aligned with evidence-based treatment goals. Your healthcare team will work with you to achieve realistic body composition improvements as part of your overall health management.

Frequently Asked Questions