Testogel is a widely prescribed testosterone replacement therapy for men with clinically confirmed hypogonadism in the UK. Understanding how long Testogel takes to work in men is essential for setting realistic expectations and ensuring treatment adherence. Whilst some improvements in mood and energy may emerge within 2 to 3 weeks, other benefits—such as enhanced libido, increased muscle mass, and improved bone density—develop more gradually over several months. Individual responses vary depending on baseline testosterone levels, application technique, lifestyle factors, and overall health. This article explains the expected timelines for Testogel's effects, the factors influencing treatment response, and the importance of proper monitoring and follow-up care.

What Is Testogel and How Does It Work?

Testogel is a transdermal testosterone replacement therapy (TRT) prescribed to men with clinically confirmed hypogonadism—a condition characterised by abnormally low testosterone levels. In the UK, Testogel is available as a 1% gel in two formulations: Testogel 50 mg/5 g sachets and Testogel 16.2 mg/g pump dispenser. It is applied once daily to clean, dry, intact skin. The application site depends on the formulation: the pump gel is applied to both shoulders and upper arms, whilst the sachet gel may be applied to the shoulders, upper arms, or abdomen. The gel must not be applied to the genital area or broken or irritated skin.

Once applied, testosterone is absorbed through the skin and enters the bloodstream, where it exerts its physiological effects. The mechanism of action involves testosterone binding to androgen receptors in various tissues, including muscle, bone, and the central nervous system. This binding initiates a cascade of cellular processes that regulate protein synthesis, bone density, libido, mood, and energy metabolism. Testosterone also undergoes peripheral conversion to dihydrotestosterone (DHT) and oestradiol, both of which contribute to its overall effects.

Testogel is licensed by the Medicines and Healthcare products Regulatory Agency (MHRA) for use in adult men with hypogonadism confirmed by clinical symptoms and biochemical testing. According to NICE Clinical Knowledge Summaries (CKS), diagnosis involves measuring serum total testosterone on at least two separate occasions (ideally early morning, fasting samples taken before 11:00) showing levels below the normal reference range, alongside symptoms such as reduced libido, erectile dysfunction, fatigue, loss of muscle mass, or mood disturbances. Additional tests—including luteinising hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG), and prolactin—help identify the underlying cause and guide referral if secondary hypogonadism or pituitary disease is suspected.

Contraindications include androgen-dependent carcinoma of the prostate or male breast cancer, and caution is required in men with severe cardiac, hepatic, or renal impairment. Men wishing to father children should be counselled that testosterone replacement suppresses spermatogenesis and may impair fertility; alternative treatments should be discussed.

How Long Does Testogel Take to Work in Men?

The timeframe for Testogel to produce noticeable effects varies depending on the symptom being addressed, and individual responses differ. Evidence from UK specialist guidance, including the British Society for Sexual Medicine (BSSM), suggests the following approximate timelines:

Early improvements in mood, energy levels, and sense of well-being may be observed within 2 to 3 weeks of starting treatment. Some men report feeling more motivated and experiencing improved sleep quality during this initial period.

Libido and sexual function typically begin to improve within 3 to 6 weeks, although the full effect may take up to 3 months. Erectile function may improve more gradually, particularly if other contributing factors (such as vascular or psychological issues) are present. It is important to note that Testogel addresses testosterone deficiency but does not directly treat erectile dysfunction caused by other mechanisms.

Physical changes, such as increased muscle mass and strength, generally become apparent after 3 to 6 months of consistent use, particularly when combined with resistance exercise. Changes in body composition, including reduced fat mass, follow a similar timeline.

Bone density improvements are slower, typically requiring 6 to 12 months or longer to become measurable. Bone density monitoring by dual-energy X-ray absorptiometry (DEXA) scanning is not routine for all men on TRT; it is indicated only for those with osteoporosis, a history of fragility fracture, or significant risk factors.

Biochemical response occurs relatively quickly: serum testosterone levels begin to rise within days of starting Testogel, and steady-state levels are typically achieved within the first few weeks. However, dose adjustments may be necessary based on follow-up blood tests. According to the Testogel Summary of Product Characteristics (SmPC), clinicians typically measure testosterone levels after the first month of treatment (timing and sampling relative to dose application vary by formulation and should follow SmPC guidance). Patients should be advised that individual responses vary, and patience is required to experience the full therapeutic benefits of testosterone replacement therapy.

Factors That Affect How Quickly Testogel Works

Several factors influence how rapidly and effectively Testogel works in individual patients. Application technique is critical: the gel must be applied to clean, dry, intact skin and allowed to dry for 3 to 5 minutes before dressing. After application, hands must be washed immediately with soap and water to prevent accidental transfer to others. The gel is flammable until dry; avoid flames or smoking during application and drying. Showering, bathing, or swimming should be avoided for a specified period after application—at least 6 hours for the pump formulation and at least 1 hour for the sachet formulation (always check the patient information leaflet for the specific product). Inconsistent application, premature washing, or failure to allow adequate drying can significantly reduce testosterone absorption and delay therapeutic effects. Covering the application site with clothing once the gel is dry provides additional protection against accidental transfer.

Skin characteristics also play a role. Men with thicker skin, excessive body hair, or dermatological conditions affecting the application site may experience reduced absorption. The gel must not be applied to broken or irritated skin, as this can lead to unpredictable absorption and higher-than-intended testosterone levels.

Baseline testosterone levels and severity of hypogonadism affect response time. Men with profoundly low testosterone may require higher doses or longer treatment duration to achieve symptom resolution compared to those with borderline deficiency. Age and overall health status are also relevant—older men or those with comorbidities such as obesity, type 2 diabetes, or metabolic syndrome may experience slower or less pronounced improvements.

Lifestyle factors significantly impact treatment outcomes. Regular physical activity, particularly resistance training, enhances the anabolic effects of testosterone on muscle mass and strength. Adequate sleep, stress management, and a balanced diet support optimal hormonal function. Conversely, excessive alcohol consumption, smoking, and sedentary behaviour can blunt the therapeutic response.

Concurrent medications may interact with testosterone. Important interactions include:

• Oral anticoagulants (e.g., warfarin): Testosterone may potentiate the effects of anticoagulants, increasing bleeding risk; more frequent INR monitoring may be required.

• Antidiabetic therapies (insulin or oral hypoglycaemics): Testosterone may improve insulin sensitivity, potentially necessitating dose adjustments to avoid hypoglycaemia.

• Corticosteroids or adrenocorticotrophic hormone (ACTH): Concurrent use may increase the risk of oedema, particularly in men with cardiac, renal, or hepatic disease.

• Certain anticonvulsants: May alter testosterone metabolism.

Patients should inform their GP of all medications and supplements they are taking to identify potential interactions that might affect treatment efficacy or safety. Consistent daily timing of application (typically in the morning) is recommended to maintain stable testosterone levels.

What to Expect During the First Weeks of Treatment

During the initial weeks of Testogel therapy, patients should be prepared for a gradual onset of benefits rather than immediate transformation. Early subjective improvements in mood, energy, and motivation are often the first signs that treatment is working. Some men describe feeling more alert, experiencing better concentration, and having improved emotional stability within the first 2 to 3 weeks.

Common side effects during the early treatment phase may include:

• Skin reactions at the application site (redness, itching, or dryness)

• Acne or oily skin, particularly on the face, chest, or back

• Mild fluid retention, causing slight weight gain or ankle swelling

• Breast tenderness or gynaecomastia (breast enlargement), due to peripheral conversion of testosterone to oestradiol

• Mood changes, including irritability or mood swings

• Hair loss (androgenic alopecia) in predisposed individuals

• Changes in blood pressure

• Increased haematocrit (red blood cell concentration), which requires monitoring through blood tests

These effects are generally mild and often resolve as the body adjusts to treatment. However, patients should contact their GP if side effects are severe, persistent, or concerning. Patients are encouraged to report any suspected adverse effects via the MHRA Yellow Card scheme (available at yellowcard.mhra.gov.uk or via the Yellow Card app).

Monitoring and follow-up are essential during the first weeks and throughout treatment. Baseline investigations before starting Testogel should include:

• Full blood count (FBC) and haematocrit

• Liver function tests

• Lipid profile

• Serum testosterone (at least two early-morning samples)

• LH, FSH, SHBG, and prolactin

• Prostate assessment: digital rectal examination (DRE) and prostate-specific antigen (PSA) measurement, tailored to the patient's age and risk factors (not limited to men over 40)

Follow-up monitoring should include:

• Testosterone levels: Measured after approximately 4 weeks of treatment (timing of blood sampling relative to gel application should follow the specific Testogel SmPC guidance for the formulation used). Dose adjustments may be necessary based on these results.

• FBC and haematocrit: Checked at 3, 6, and 12 months, then annually. If haematocrit exceeds 54%, consider dose reduction, temporary discontinuation, or investigation for underlying causes (e.g., obstructive sleep apnoea). Persistent erythrocytosis may require referral to haematology.

• Prostate monitoring: DRE and PSA should be repeated at regular intervals (e.g., 3 and 6 months, then annually), tailored to individual risk.

• Bone density (DEXA): Only if clinically indicated (e.g., osteoporosis, fragility fracture, or significant risk factors).

Patient safety advice is paramount:

• Prevent accidental transfer: Wash hands immediately after application. Cover the application site with clothing once the gel is dry. Avoid skin-to-skin contact with partners, children, or other household members for several hours after application. If accidental contact occurs, the exposed person should wash the affected skin promptly with soap and water. Testosterone transfer can cause virilisation in women and children (e.g., increased body hair, acne, genital changes).

• Fertility counselling: Men should be informed that testosterone replacement therapy suppresses spermatogenesis and may impair fertility. Those wishing to father children should discuss alternative treatments with their GP or specialist.

• Realistic expectations: While Testogel effectively treats hypogonadism, it is not a cure-all for every symptom. Comprehensive lifestyle modification—including regular exercise, healthy diet, adequate sleep, and stress management—remains important for optimal health outcomes.

Frequently Asked Questions