Testogel is a transdermal testosterone replacement therapy licensed in the UK for treating male hypogonadism, a condition characterised by abnormally low testosterone levels. Applied daily to the shoulders and upper arms, the gel delivers testosterone through the skin, bypassing the liver and providing relatively stable hormone levels. Clinical evidence demonstrates that Testogel effectively normalises testosterone concentrations in men with confirmed deficiency, leading to improvements in libido, energy, mood, and quality of life. However, it works specifically for diagnosed hypogonadism—not for performance enhancement or anti-ageing in men with normal testosterone—and requires careful patient selection, proper application technique, and ongoing medical monitoring to ensure safety and efficacy.

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 characterised by abnormally low testosterone levels. The current UK-licensed formulation is Testogel 16.2 mg/g gel, supplied in pump or sachet form. It is applied once daily to clean, dry skin on the shoulders and upper arms only. The gel is absorbed through the skin, delivering testosterone directly into the bloodstream and bypassing first-pass hepatic metabolism.

The mechanism of action involves supplementing endogenous testosterone to restore physiological levels. Once absorbed, testosterone binds to androgen receptors throughout the body, influencing multiple systems including muscle and bone metabolism, sexual function, mood regulation, and erythropoiesis (red blood cell production). The transdermal route provides relatively steady day-to-day serum testosterone concentrations compared with intramuscular injections, which can produce more pronounced peaks and troughs.

Testogel is formulated to dry quickly on the skin, forming a reservoir from which testosterone is gradually released over 24 hours. This sustained-release profile provides more stable testosterone levels than injections, though it does not reproduce the body's natural early-morning peak seen with endogenous production. The gel must be applied consistently at approximately the same time each day to maintain stable therapeutic levels.

Important application and safety considerations include:

• Apply only to the shoulders and upper arms—never to the genitals, abdomen, or broken or irritated skin

• Allow the gel to dry completely before dressing (typically 3–5 minutes)

• Wash hands thoroughly with soap and water immediately after application

• The gel is alcohol-based and flammable until dry—avoid naked flames and do not smoke during or immediately after application

• Cover the application site with clothing once dry

• To prevent inadvertent testosterone transfer to partners or children, wash the application site with soap and water before any situation where close skin-to-skin contact is anticipated, or wait at least 2 hours before showering or swimming

• Avoid direct skin-to-skin contact with others at application sites until the area has been washed

These precautions minimise the risk of testosterone transfer to partners or children, which can cause virilisation in women (acne, excess body hair, voice deepening) or premature sexual development in children—a significant safety concern with all transdermal testosterone preparations.

Clinical Evidence: Does Testogel Work for Low Testosterone?

Robust clinical evidence supports the efficacy of testosterone gel in normalising serum testosterone levels in men with confirmed hypogonadism. Multiple randomised controlled trials and real-world studies demonstrate that transdermal testosterone gel consistently raises total and free testosterone concentrations into the physiological range in the majority of appropriately selected patients. Normal reference ranges are assay-dependent but typically fall around 8–30 nmol/L for total testosterone in UK laboratories.

Pivotal studies submitted to the European Medicines Agency (EMA) for testosterone gel products show that the majority of men with hypogonadism achieve target testosterone levels within the normal reference range after dose optimisation. Importantly, these biochemical improvements translate into clinically meaningful benefits: participants in controlled trials report significant improvements in libido, erectile function, energy levels, and overall quality of life compared to baseline measurements. Mood parameters, including symptoms of depression and irritability, also show statistically significant improvement in several trials.

NICE Clinical Knowledge Summary (CKS) on testosterone deficiency in adult males and guidance from the UK Society for Endocrinology and British Society for Sexual Medicine (BSSM) acknowledge testosterone replacement therapy as an appropriate treatment for men with confirmed hypogonadism. Diagnosis requires consistently low testosterone levels on at least two morning samples (taken before 11 am), accompanied by relevant symptoms. TRT should only be initiated after excluding reversible causes of low testosterone, such as obesity, poorly controlled type 2 diabetes, obstructive sleep apnoea, certain medications (e.g., opioids, glucocorticoids), or excessive alcohol intake. The evidence base is strongest for men with organic hypogonadism (testicular or pituitary pathology) rather than age-related decline alone.

Important limitations and warnings:

• Testogel works specifically for testosterone deficiency—it will not provide benefits in men with normal testosterone levels

• There is no evidence supporting use for athletic performance enhancement or anti-ageing in men with normal testosterone (eugonadal men), and such use is not licensed

• TRT suppresses sperm production (spermatogenesis) and is not suitable for men actively trying to conceive. Men wishing to father children should be referred to endocrinology or andrology for alternative treatments such as gonadotrophin therapy

• For late-onset (age-related) hypogonadism, UK guidance emphasises that lifestyle modifications—including weight loss, increased physical activity, improved sleep quality, and optimised management of comorbidities—should be attempted first, as these interventions can naturally raise testosterone levels

• Response rates vary, and approximately 10–15% of patients may require dose adjustment or alternative formulations to achieve optimal results

Expected Results and Timeline for Testogel Treatment

Understanding the timeline for Testogel's effects helps set realistic patient expectations and supports treatment adherence. Different symptoms respond at varying rates, reflecting the diverse physiological actions of testosterone across multiple organ systems. Timelines are based on UK specialist guidance and clinical trial data.

Early improvements (within 2–4 weeks) typically include:

• Enhanced libido and sexual interest

• Improved mood and sense of wellbeing

• Increased energy levels and reduced fatigue

• Better concentration and mental clarity

These initial changes often occur before testosterone levels have fully stabilised, possibly reflecting both pharmacological effects and psychological factors associated with treatment initiation.

Intermediate effects (3–6 months) encompass:

• Improvements in erectile function and sexual performance

• Increased muscle mass and strength (particularly when combined with resistance exercise)

• Reduction in fat mass, especially visceral adiposity

• Gradual increases in haemoglobin and haematocrit (red blood cell parameters)

Longer-term benefits (6–12 months and beyond) include continued improvements in body composition, sustained sexual function, and progressive increases in bone mineral density. Clinically meaningful improvements in bone density typically require at least 12 months of ongoing therapy.

Dose optimisation for Testogel 16.2 mg/g usually occurs after the first few weeks of treatment. The typical starting dose is 40.5 mg (2.5 g gel) once daily, which can be adjusted in steps of 20.25 mg (1.25 g gel) based on clinical response and serum testosterone measurements. The usual maintenance dose range is 40.5–81 mg daily. Blood samples for testosterone monitoring should be taken at steady state (after at least one week of consistent dosing) and timed according to the product's pharmacokinetic profile—your doctor will advise on the appropriate timing for your formulation.

Patients should attend regular monitoring appointments to assess both biochemical response and symptomatic improvement. It is crucial to understand that Testogel requires ongoing, consistent use—benefits diminish if treatment is discontinued, as the underlying hypogonadism remains. Patience during the initial months is essential, as maximal therapeutic effects develop progressively rather than immediately. Individual responses vary, and some men may require several months and dose adjustments to achieve optimal benefit.

Who Benefits Most from Testogel Therapy?

Testogel is specifically indicated for men with confirmed hypogonadism—a diagnosis requiring both biochemical evidence (persistently low testosterone levels on at least two morning samples taken before 11 am) and relevant clinical symptoms. The therapy works most effectively in clearly defined patient groups where testosterone deficiency has been properly established and reversible causes have been excluded or addressed.

Primary hypogonadism (testicular failure) represents an ideal indication. This includes men with:

• Klinefelter syndrome or other genetic conditions affecting testicular function

• Testicular damage from chemotherapy, radiotherapy, or trauma

• Bilateral orchidectomy (surgical removal of testes)

• Mumps orchitis or other infectious causes of testicular failure

These patients typically show excellent, predictable responses to Testogel, as the therapy directly replaces the missing hormone.

Secondary hypogonadism (hypothalamic-pituitary dysfunction) also responds well, including conditions such as:

• Pituitary tumours or hypopituitarism

• Kallmann syndrome

• Hyperprolactinaemia (after treating the underlying cause)

• Certain chronic illnesses affecting the hypothalamic-pituitary-gonadal axis

Age-related (late-onset) hypogonadism presents a more nuanced picture. NICE CKS and UK specialist guidance suggest that whilst some older men with genuinely low testosterone and bothersome symptoms may benefit, treatment decisions should be individualised and made only after a trial of lifestyle interventions. Weight loss, increased physical activity, improved sleep hygiene, reduced alcohol intake, and optimised management of comorbidities such as type 2 diabetes and obstructive sleep apnoea should be attempted first, as these interventions can naturally raise testosterone levels and may obviate the need for TRT.

Important considerations for patient selection:

Men who require optimisation before or alongside TRT:

• Untreated obstructive sleep apnoea (treat first; may improve testosterone naturally)

• Severe obesity (weight loss often raises testosterone)

• Poorly controlled type 2 diabetes or other chronic diseases

• Medication review (opioids, glucocorticoids, and some other drugs lower testosterone)

Men who are unlikely to benefit or for whom TRT is inappropriate:

• Normal testosterone levels (TRT will not enhance performance or vitality in eugonadal men)

• Non-specific symptoms (e.g., fatigue, low mood) without biochemical confirmation of hypogonadism

• Men actively trying to conceive—TRT suppresses sperm production and is not a fertility treatment. These men should be referred to endocrinology or andrology for alternative management, such as gonadotrophin therapy, which can stimulate both testosterone production and spermatogenesis

• Men with prostate cancer, male breast cancer, or significantly elevated PSA (Testogel is contraindicated)

Careful patient selection, based on thorough endocrine assessment, exclusion of reversible causes, and consideration of fertility intentions, maximises treatment success and minimises inappropriate prescribing.

Potential Side Effects and Safety Considerations

Understanding potential adverse effects is essential for informed decision-making and safe Testogel use. Whilst many men tolerate the therapy well, all patients should be aware of possible complications and monitoring requirements.

Common local reactions include:

• Skin irritation, redness, or itching at application sites (affecting approximately 5–10% of users)

• Dry skin or contact dermatitis

• Acne or oily skin, particularly during initial treatment

Rotating application sites between shoulders and upper arms and ensuring skin is completely dry before application can minimise these effects. Persistent or severe skin reactions may necessitate switching to alternative testosterone formulations.

Systemic side effects that require monitoring include:

• Polycythaemia (elevated red blood cell count)—the most clinically significant concern. TRT stimulates red blood cell production, and excessive haematocrit (≥0.54 or 54%) increases the risk of blood clots (thrombosis). Regular full blood count monitoring is mandatory. If haematocrit rises above this threshold, dose reduction or temporary treatment cessation may be required.

• Venous thromboembolism (VTE)—blood clots in the legs (deep vein thrombosis) or lungs (pulmonary embolism) have been reported with testosterone therapy. Seek urgent medical attention if you develop severe leg swelling, chest pain, sudden breathlessness, or coughing up blood.

• Prostate effects—whilst there is no established causal link between physiological testosterone replacement and prostate cancer development, TRT can stimulate existing prostate tissue. UK guidance recommends baseline risk assessment and discussion of prostate-specific antigen (PSA) testing and digital rectal examination (DRE) based on age, family history, and individual risk factors, using a shared decision-making approach. Ongoing monitoring of PSA and assessment for lower urinary tract symptoms should continue during treatment as advised by your doctor.

• Cardiovascular considerations—fluid retention and oedema can occur, particularly in men with pre-existing cardiac, renal, or hepatic impairment. TRT should be used with caution in these conditions. Discuss any history of heart disease with your doctor before starting treatment.

• Reduced fertility—TRT suppresses the body's own testosterone and sperm production. Men may experience reduced sperm count or temporary infertility. This effect is usually reversible after stopping treatment, but recovery can take many months. TRT is not suitable for men trying to conceive.

• Other recognised effects include: – Gynaecomastia (breast enlargement) or breast tenderness – Mood changes, including increased irritability or aggression (though many men experience mood improvement) – Hair loss or male-pattern baldness – Changes in libido – Sleep apnoea worsening in susceptible individuals – Hypertension (high blood pressure)

Transfer risk represents a unique concern with transdermal preparations. Inadvertent testosterone transfer to female partners or children through skin-to-skin contact can cause virilisation in women (acne, excess body hair, voice deepening) or premature sexual development in children. Strict precautions include:

• Allowing the gel to dry completely before dressing

• Covering application sites with clothing

• Washing hands thoroughly with soap and water immediately after application

• Washing the application site with soap and water before any anticipated close skin-to-skin contact (e.g., intimate contact, holding children)

• Waiting at least 2 hours after application before showering or swimming

Contraindications (when Testogel must not be used) include:

• Prostate cancer or male breast cancer

• Known or suspected hypersensitivity to testosterone or any excipients

Use with caution (discuss with your doctor) if you have:

• Severe heart, liver, or kidney disease

• Polycythaemia or significantly elevated haematocrit

• Untreated or poorly controlled obstructive sleep apnoea

• Epilepsy or migraine (may worsen)

When to seek urgent medical attention:

• Chest pain or pressure

• Severe leg swelling, pain, or redness

• Sudden breathlessness or coughing up blood

• Signs of stroke (sudden weakness, speech difficulty, facial drooping)

• Persistent painful erections lasting more than 4 hours (priapism)

• Severe allergic reaction (rash, swelling of face/throat, difficulty breathing)

Regular monitoring is essential for safe, effective long-term therapy. Your GP or specialist will typically arrange:

• Baseline assessments before starting treatment: testosterone levels (two morning samples), full blood count, PSA (with discussion of risks/benefits), liver function tests, lipid profile, and assessment of cardiovascular risk factors

• Follow-up at 3 months, then 6 months, then annually (or more frequently if needed): testosterone levels (to guide dosing), full blood count (haematocrit monitoring), PSA, liver function, lipids, and symptom review

Reporting side effects: If you experience any side effects, talk to your doctor or pharmacist. This includes any possible side effects not listed here. You can also report 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. By reporting side effects, you can help provide more information on the safety of this medicine.

Frequently Asked Questions