Testogel is a prescription testosterone replacement therapy (TRT) gel licensed in the UK for treating male hypogonadism—a medical condition where the testes produce insufficient testosterone. Applied daily to the skin, Testogel delivers bioidentical testosterone directly into the bloodstream, helping to restore hormone levels to the normal physiological range. It is available in two formulations: 50 mg/5 g sachets and a 16.2 mg/g pump. This article explains what Testogel does for men with confirmed testosterone deficiency, how it works, its benefits, proper usage, and important safety considerations. Testogel is not licensed for bodybuilding, performance enhancement, or age-related testosterone decline in otherwise healthy men.

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 testes produce insufficient testosterone. It is available in two formulations: Testogel 50 mg/5 g (1%) sachets and Testogel 16.2 mg/g (1.62%) pump, both applied daily to the skin. The active ingredient is bioidentical testosterone, chemically identical to the hormone naturally produced by the body.

The mechanism of action involves absorption of testosterone through the skin into the bloodstream, where it binds to androgen receptors throughout the body. Once absorbed, testosterone exerts its effects on multiple organ systems, including muscle tissue, bone, the central nervous system, and reproductive organs. The gel formulation provides relatively steady serum testosterone levels with fewer peaks and troughs than some other forms of TRT such as intramuscular injections.

Testogel is specifically indicated for men with confirmed testosterone deficiency, which must be demonstrated through two separate early-morning blood tests showing low total testosterone levels, taken when levels are naturally highest. Diagnosis also requires assessment of symptoms (such as fatigue, reduced libido, and mood changes), measurement of luteinising hormone (LH), follicle-stimulating hormone (FSH), and sex hormone-binding globulin (SHBG), and consideration of free or bioavailable testosterone. Laboratory reference ranges vary by assay and age, so interpretation should be individualised. The MHRA emphasises that testosterone replacement should only be initiated after thorough clinical and biochemical evaluation, as symptoms of low testosterone can overlap with many other conditions.

It is important to note that Testogel is not licensed for performance enhancement, bodybuilding, or age-related decline in testosterone in otherwise healthy men (sometimes called 'andropause'). Prescribing should follow guidance from the Society for Endocrinology and the British Society for Sexual Medicine (BSSM), ensuring that treatment addresses a genuine medical need rather than lifestyle concerns.

Benefits and Expected Effects of Testogel Treatment

When used appropriately for confirmed hypogonadism, Testogel can produce several clinically meaningful benefits by restoring testosterone levels to the mid-normal physiological range appropriate for the patient's age and laboratory assay. The primary therapeutic goals include:

• Improved sexual function: Many men experience enhanced libido, improved erectile function, and increased sexual satisfaction. However, response varies individually, and testosterone replacement alone may not resolve erectile dysfunction if other factors (vascular, psychological, or neurological) are present.

• Increased muscle mass and strength: Testosterone promotes protein synthesis in skeletal muscle. Men often notice gradual improvements in muscle tone and physical strength over several months, particularly when combined with resistance exercise.

• Enhanced mood and sense of wellbeing: Some men with confirmed hypogonadism report improvements in mood, energy levels, concentration, and overall sense of wellbeing. Evidence for cognitive benefits is variable and most consistent in symptomatic hypogonadal men; effects should not be expected in men with normal testosterone levels.

• Bone density preservation: Testosterone plays a crucial role in maintaining bone mineral density. Long-term treatment may help reduce the risk of osteoporosis and fractures in men with hypogonadism, though clinically meaningful increases in bone density typically require at least 6–12 months of therapy and may continue for up to two years.

• Body composition changes: Patients may experience a reduction in fat mass, particularly visceral (abdominal) fat, alongside increases in lean body mass over several months.

The timeline for these effects varies considerably. Sexual symptoms may improve within a few weeks, whilst changes in body composition and muscle mass typically require several months. Bone density improvements generally take at least 6–12 months and may continue for up to two years. It is essential to maintain realistic expectations: Testogel restores deficient testosterone to normal levels but does not produce supraphysiological effects. Regular monitoring through blood tests (typically at around 3 months after initiation or dose adjustment, then at least annually) ensures treatment remains effective and safe. Monitoring should include full blood count (FBC) and haematocrit at baseline, 3–6 months, then annually, with dose reduction or temporary cessation if haematocrit exceeds 54%. Prostate-specific antigen (PSA) and digital rectal examination (if clinically indicated) should be performed at baseline and periodically thereafter according to individual risk and UK guidance.

How to Use Testogel Safely and Effectively

Correct application technique is crucial for optimal absorption and to minimise the risk of transferring testosterone to others. Dosing and application instructions differ between the two Testogel formulations:

Testogel 50 mg/5 g (1%) sachets: The usual starting dose is 50 mg daily (one 5 g sachet), applied once each morning to clean, dry, intact skin on the shoulders, upper arms, or abdomen. Your prescriber may adjust the dose based on blood testosterone levels, typically measured in the morning before the next application.

Testogel 16.2 mg/g (1.62%) pump: The usual starting dose is 40.5 mg daily (two pump actuations), applied once each morning to clean, dry, intact skin on the shoulders and upper arms only (not the abdomen). Blood testosterone levels are typically measured 2–4 hours after application to guide dose adjustment.

Application instructions for both formulations:

• Spread the gel thinly over a large area to maximise absorption. Allow it to dry for 3–5 minutes before dressing.

• Wash your hands thoroughly with soap and water immediately after application.

• Cover the application site with clothing once dry to prevent accidental transfer to others through skin-to-skin contact.

• Avoid swimming or showering for at least 6 hours after applying Testogel 1% sachets, or at least 2 hours after applying Testogel 16.2 mg/g pump, to ensure adequate absorption.

Critical safety precautions include preventing transfer to women and children, as even small amounts of testosterone can cause virilisation in females (deepening voice, facial hair growth) and premature puberty in children. If direct skin contact occurs, the affected area should be washed immediately with soap and water. Partners and family members should be informed of these risks.

Patients should attend regular follow-up appointments for monitoring, which typically includes:

• Testosterone levels (to ensure mid-normal physiological range for age and assay)

• Full blood count and haematocrit (testosterone can increase red blood cell production; if haematocrit exceeds 54%, dose reduction or temporary cessation and investigation are required)

• Prostate-specific antigen (PSA) at baseline and periodically thereafter, with digital rectal examination if clinically indicated, according to individual risk and local protocols

• Liver function tests and lipid profile if clinically indicated

According to the Summary of Product Characteristics (SmPC) and MHRA guidance, Testogel is contraindicated in men with known or suspected prostate cancer or male breast cancer. Cardiovascular disease is a caution requiring careful individual risk assessment rather than an absolute contraindication. Men with polycythaemia (elevated haematocrit) should have this corrected before starting treatment. Always inform your GP of any new medications or health changes during treatment.

Potential Side Effects and Risks of Testogel

Like all medicines, Testogel can cause side effects, though not everyone experiences them. Understanding potential adverse effects enables early recognition and appropriate management.

Common side effects include:

• Skin reactions at the application site: redness, itching, dry skin, or acne. These are usually mild and resolve with continued use or by rotating application sites.

• Increased haematocrit and haemoglobin: Testosterone stimulates red blood cell production, which can lead to polycythaemia (excessive red blood cells). This increases blood viscosity and may raise cardiovascular risk. Regular blood monitoring is essential, and if haematocrit exceeds 54%, dose reduction or temporary cessation and investigation are required.

• Gynaecomastia (breast enlargement) and breast tenderness may occur in some men.

• Fluid retention and oedema: Some men experience swelling, particularly of the ankles, or weight gain due to fluid retention.

• Changes in blood pressure: Both increases and decreases in blood pressure have been reported.

• Prostate changes: Testosterone can stimulate benign prostatic hyperplasia (BPH), causing urinary symptoms such as hesitancy, frequency, or nocturia. Whilst there is no definitive evidence that testosterone therapy causes prostate cancer, existing prostate cancer may be stimulated by testosterone. Baseline and periodic PSA monitoring according to individual risk and UK guidance is important.

• Mood and behavioural changes: Some men report increased irritability, aggression, or mood swings, particularly if testosterone levels become supraphysiological.

• Hair loss (alopecia) may occur or worsen in predisposed individuals.

Less common but serious risks include:

• Cardiovascular events: The relationship between testosterone therapy and cardiovascular risk remains an area of ongoing research and debate. The MHRA advises careful cardiovascular risk assessment before initiating treatment and ongoing monitoring, particularly in older men or those with pre-existing cardiovascular disease.

• Venous thromboembolism (VTE): The MHRA has issued warnings regarding an increased risk of deep vein thrombosis or pulmonary embolism, particularly in men with thrombophilia or a history of VTE. Increased haematocrit may further elevate this risk.

• Sleep apnoea: Testosterone can worsen obstructive sleep apnoea; men with this condition require specialist assessment before and during treatment.

• Fertility suppression: Testosterone therapy suppresses the hypothalamic-pituitary-gonadal axis, reducing sperm production. Men wishing to father children should discuss alternative treatments with their specialist.

When to seek medical advice: Contact your GP or seek urgent medical attention if you experience chest pain, shortness of breath, sudden severe headache, leg swelling or pain, signs of a severe allergic reaction (such as difficulty breathing or swelling of the face or throat), prolonged or painful erection (priapism), jaundice (yellowing of the skin or eyes), or marked oedema with rapid weight gain. Routine concerns such as skin irritation or mild acne can be discussed at your next scheduled appointment. Never adjust your dose without medical supervision, and inform all healthcare professionals that you are using testosterone replacement therapy.

If you experience any side effects, including those not listed here, you can report them via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or through the Yellow Card app. Reporting helps improve the safety information available about medicines.

Frequently Asked Questions