Testogel is a prescription-only testosterone replacement therapy licensed in the UK for adult males with confirmed hypogonadism—a condition where the body cannot produce adequate testosterone. Available as a transdermal gel applied daily to the skin, Testogel delivers testosterone directly into the bloodstream, helping restore normal hormone levels. Diagnosis requires two separate morning blood tests showing low serum testosterone alongside clinical symptoms such as reduced libido, fatigue, loss of muscle mass, and low mood. Treatment must be initiated and monitored by a qualified healthcare professional, typically an endocrinologist, with regular follow-up to assess efficacy and detect potential side effects.

What Is Testogel and How Does It Work?

Testogel is a transdermal testosterone replacement therapy (TRT) available in the UK as a clear, colourless gel containing testosterone as the active ingredient. It is applied directly to the skin, where the hormone is absorbed into the bloodstream. Testogel is manufactured by Besins Healthcare and is available in two formulations:

• Testogel 50 mg/5 g (1%) gel in single-use sachets: Each sachet contains 50 mg testosterone in 5 g of gel. The usual starting dose is one sachet (50 mg) applied once daily.

• Testogel 16.2 mg/g (1.62%) gel in metered-dose pump: Each pump actuation delivers approximately 20.25 mg of testosterone. The usual starting dose is two actuations (approximately 40.5 mg) applied once daily.

The mechanism of action involves supplementing endogenous testosterone in men whose bodies do not produce adequate amounts of this essential androgen hormone. Once absorbed through the skin, testosterone enters the systemic circulation and binds to androgen receptors throughout the body. This helps restore normal physiological testosterone levels, which are crucial for numerous bodily functions including sexual development, muscle mass maintenance, bone density, red blood cell production, and overall wellbeing.

Testosterone replacement works by mimicking the body's natural hormone production. In healthy males, testosterone is primarily produced by the Leydig cells in the testes, with smaller amounts synthesised by the adrenal glands. When natural production is insufficient—a condition known as hypogonadism—external supplementation through preparations like Testogel can help restore hormonal balance. The transdermal route offers steady absorption and avoids the first-pass hepatic metabolism associated with oral testosterone preparations, providing more stable serum testosterone levels throughout the day. This delivery method also allows for dose adjustments based on individual patient response and monitoring of testosterone levels.

Application sites differ by formulation: The 1% sachets may be applied to the shoulders, upper arms, or abdomen. The 16.2 mg/g pump formulation should be applied only to the shoulders and upper arms (not the abdomen). The gel should never be applied to the genital area. Important safety note: Testogel is flammable until dry. Avoid open flames and do not smoke during and immediately after application until the gel has completely dried.

What Conditions Does Testogel Treat?

Testogel is licensed in the UK specifically for testosterone replacement therapy in adult males with hypogonadism. Hypogonadism is a clinical condition characterised by the body's inability to produce normal amounts of testosterone due to problems with the testes (primary hypogonadism) or with the pituitary gland and hypothalamus (secondary hypogonadism). This deficiency must be confirmed through both clinical symptoms and biochemical evidence.

Diagnosis requires:

• Two separate morning blood tests (ideally taken between 8 and 11 am) showing low serum testosterone levels

• Interpretation of results: Total testosterone <8 nmol/L is generally considered low; levels between 8–12 nmol/L are borderline and should be interpreted alongside sex hormone-binding globulin (SHBG) and calculated free testosterone, as well as clinical symptoms

• Further investigations to identify the underlying cause: luteinising hormone (LH), follicle-stimulating hormone (FSH), prolactin, SHBG, thyroid function, and ferritin/iron studies. Pituitary imaging may be required if secondary hypogonadism is suspected

Clinical features of hypogonadism that Testogel aims to address include:

• Sexual dysfunction: reduced libido, erectile dysfunction, and decreased sexual activity

• Physical changes: loss of muscle mass and strength, increased body fat (particularly abdominal), reduced bone mineral density leading to osteoporosis risk

• Psychological symptoms: low mood, irritability, poor concentration, reduced energy, and fatigue

• Other manifestations: reduced facial and body hair growth, and gynaecomastia (breast tissue development)

According to NICE Clinical Knowledge Summaries (CKS), testosterone replacement should only be initiated when there is clear biochemical evidence of testosterone deficiency alongside relevant symptoms. The Medicines and Healthcare products Regulatory Agency (MHRA) emphasises that testosterone preparations like Testogel are not indicated for age-related low testosterone in the absence of an identified pathological cause, nor should they be used for performance enhancement or bodybuilding purposes.

Important fertility consideration: Testogel is not a treatment for infertility. Testosterone replacement therapy suppresses spermatogenesis (sperm production) and is contraindicated in men who are actively trying to conceive. Men wishing to preserve or restore fertility should be referred to an endocrinologist or andrologist to discuss alternative treatments such as human chorionic gonadotrophin (hCG).

It is important to note that whilst some men may experience declining testosterone levels with age (sometimes termed 'andropause' or late-onset hypogonadism), there is no official indication for treating age-related testosterone decline unless it meets the diagnostic criteria for hypogonadism with associated symptoms and significantly low testosterone levels confirmed by laboratory testing.

Who Can Use Testogel in the UK?

Testogel is a prescription-only medicine (POM) in the UK and should only be used under the supervision of a qualified healthcare professional. Treatment is typically initiated by an endocrinologist or specialist with expertise in male reproductive health, though ongoing management may be shared with primary care under local shared-care protocols. The decision to prescribe Testogel requires careful patient selection based on established diagnostic criteria and consideration of potential contraindications.

Suitable candidates for Testogel therapy include adult males (typically over 18 years) who have:

• Confirmed biochemical hypogonadism with two separate morning serum testosterone measurements showing levels consistently below the normal reference range

• Clear clinical symptoms attributable to testosterone deficiency

• No absolute contraindications to testosterone therapy

• Completed appropriate baseline investigations to exclude underlying pathology

Absolute contraindications to Testogel use (as per the Summary of Product Characteristics) include:

• Known or suspected prostate cancer or male breast cancer (current or previous)

• Hypersensitivity to testosterone or any excipients in the formulation

• Testogel is not licensed for use in women or children

Cautions requiring careful risk-benefit assessment and close monitoring include:

• Severe cardiac, hepatic, or renal insufficiency or ischaemic heart disease (risk of complications including fluid retention and oedema)

• Benign prostatic hyperplasia with significant urinary symptoms

• Epilepsy and migraine (may be exacerbated)

• Obstructive sleep apnoea (may be worsened by testosterone therapy)

• Conditions that may be exacerbated by fluid retention

• Polycythaemia: Therapy should not be initiated or should be paused if haematocrit exceeds 0.54 (54%). The cause should be investigated and treated, and therapy resumed only when it is safe to do so

Important note on fertility: Men who are actively trying to conceive should not use Testogel, as testosterone replacement suppresses spermatogenesis. These men should be referred to specialist care to discuss fertility-preserving alternatives.

Testogel should never be applied to female partners or children due to the risk of virilisation (development of male characteristics). Pregnant or breastfeeding women must avoid any contact with Testogel application sites.

Baseline assessments are essential before initiating treatment:

• Repeat morning total testosterone to confirm diagnosis

• Hormonal profile: LH, FSH, SHBG, prolactin

• Prostate assessment: Digital rectal examination (DRE) and prostate-specific antigen (PSA) testing in men over 40 years or those at increased prostate cancer risk

• Full blood count (to check haematocrit and haemoglobin)

• Metabolic and cardiovascular screening: Blood pressure, lipid profile, fasting glucose or HbA1c

• Iron studies (ferritin) if indicated

• Pituitary imaging if secondary hypogonadism is suspected (low testosterone with low or inappropriately normal LH/FSH, or other pituitary hormone deficiencies)

These investigations help identify any pre-existing conditions that might contraindicate testosterone therapy or require closer monitoring.

How to Apply Testogel Safely and Effectively

Correct application technique is crucial for ensuring optimal absorption, therapeutic efficacy, and minimising the risk of inadvertent transfer to others. Testogel should be applied once daily, preferably at the same time each day (typically in the morning) to mimic the body's natural circadian rhythm of testosterone production.

Step-by-step application guidance:

1. Prepare the application site: Choose clean, dry, intact skin. Application sites differ by formulation:

2. 1% sachets: Apply to the shoulders, upper arms, or abdomen

3. 16.2 mg/g pump: Apply to the shoulders and upper arms only (do not apply to the abdomen)

4. Never apply to the genital area, as this increases the risk of transfer to partners. Do not apply to broken, irritated, or recently shaved skin. Rotate application sites to minimise skin irritation.

5. Apply the gel: Open the sachet completely or use the pump dispenser as directed. Squeeze the entire contents of the sachet (single-use only; discard after use) or the prescribed number of pump actuations onto the application site and spread thinly over a large area using your finger. Do not rub vigorously—gentle spreading is sufficient. Do not cover the application site with an occlusive dressing.

6. Allow to dry: Let the gel dry for 3–5 minutes before dressing. The gel is flammable until dry—avoid open flames and do not smoke during and immediately after application. The application site should be covered with clothing once dry to prevent transfer to others through skin-to-skin contact.

7. Wash hands thoroughly: Immediately after application, wash your hands with soap and water to remove any residual gel.

Important safety precautions to prevent testosterone transfer:

• Avoid skin-to-skin contact with others (particularly women and children) at the application site for at least 6 hours after application

• Cover the application site with clothing once the gel has dried

• Wash the application site thoroughly with soap and water before any situation where close skin contact is anticipated (e.g., intimate contact, contact with children)

• If accidental skin contact occurs, the affected person should wash the contact area with soap and water immediately

• Wash clothing and bed linen regularly, as testosterone can transfer to fabrics

Timing considerations: If you forget a dose, apply it as soon as you remember on the same day. If it is nearly time for the next dose, skip the missed dose—do not apply a double dose. Showering and swimming: To ensure optimal absorption, avoid showering, bathing, or swimming for at least 6 hours after application. Washing the application site earlier may reduce the amount of testosterone absorbed. Consistency in application timing and technique helps maintain stable testosterone levels and improves treatment outcomes.

Potential Side Effects and Safety Considerations

Like all medicines, Testogel can cause side effects, though not everyone experiences them. Understanding potential adverse effects helps patients recognise when to seek medical advice and enables informed decision-making about treatment continuation.

Common side effects (frequencies as per the Summary of Product Characteristics) include:

• Skin reactions at application site: redness, itching, dry skin, acne, or allergic contact dermatitis

• Prostate-related changes: elevated PSA levels, benign prostatic hyperplasia

• Erythrocytosis: increased red blood cell count, raised haematocrit and haemoglobin (which increases blood viscosity and thrombotic risk)

• Headache and dizziness

• Mood and behavioural changes: mood swings, increased aggression, irritability, or anxiety

• Changes in libido: either increased or, paradoxically, decreased sexual desire

• Gynaecomastia: breast tenderness or enlargement

• Peripheral oedema and fluid retention

• Hypertension (raised blood pressure)

• Weight gain

Serious but less common side effects requiring prompt medical attention include:

• Cardiovascular events: chest pain, shortness of breath, or signs of heart attack or stroke. The MHRA has issued safety warnings that testosterone therapy may be associated with increased cardiovascular risk in some patient populations, particularly those with pre-existing cardiovascular disease, though the evidence remains under review.

• Polycythaemia/erythrocytosis: Excessive red blood cell production increases blood viscosity and the risk of thrombosis (blood clots). Symptoms may include headache, visual disturbances, flushing, or unexplained leg swelling.

• Severe allergic reactions: difficulty breathing, swelling of face or throat, severe skin reactions

• Priapism: prolonged, painful erection lasting more than 4 hours (requires emergency medical attention)

• Sleep apnoea: Testosterone may worsen obstructive sleep apnoea in predisposed men. Be alert for loud snoring, witnessed breathing pauses during sleep, or excessive daytime sleepiness.

• Hepatic dysfunction: Although rare with transdermal testosterone, seek medical advice if you develop jaundice (yellowing of skin or eyes), dark urine, or persistent nausea

Important drug interactions:

• Anticoagulants (e.g., warfarin): Testosterone may enhance the anticoagulant effect, increasing bleeding risk. More frequent monitoring of INR (international normalised ratio) may be required.

• Antidiabetic medicines (insulin, oral hypoglycaemics): Testosterone may alter blood glucose control; monitor blood glucose levels and adjust antidiabetic therapy as needed.

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

When to contact your GP or healthcare provider:

• Persistent or severe skin reactions at application sites

• Significant mood changes, depression, or aggressive behaviour

• Urinary symptoms such as difficulty passing urine, increased frequency, or weak stream

• Unexplained leg swelling, persistent headaches, visual disturbances, or flushing

• Any signs of cardiovascular problems (chest pain, breathlessness, palpitations)

• Symptoms suggesting sleep apnoea (loud snoring, witnessed apnoeas, excessive daytime sleepiness)

• Prolonged or painful erection

Patients should also be aware that inadvertent transfer to others can cause virilisation in women (deepening voice, facial hair growth, menstrual irregularities, acne) and premature sexual development in children (early puberty, genital enlargement, aggressive behaviour). If transfer is suspected, the affected person should wash the area immediately with soap and water and seek medical advice.

Reporting side effects: If you experience any side effects, talk to your doctor or pharmacist. 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. Reporting helps provide more information on the safety of medicines.

Monitoring and Follow-Up Care with Testogel

Regular monitoring is essential for patients using Testogel to ensure treatment efficacy, detect potential adverse effects early, and adjust dosing as needed. NICE Clinical Knowledge Summaries (CKS) and the Specialist Pharmacy Service (SPS) recommend structured follow-up protocols for all men receiving testosterone replacement therapy.

Initial monitoring phase (first 3–6 months):

• Testosterone levels: Measured approximately 2–4 weeks after starting treatment or after any dose adjustment to guide titration, then again at 3–6 months once the dose is stable. Blood samples should be taken in the morning before the daily dose (trough levels) to evaluate steady-state concentrations. The aim is to achieve testosterone levels in the normal reference range for adult men.

• Clinical response assessment: Evaluation of symptom improvement, including sexual function, energy levels, mood, and physical changes (muscle mass, body composition)

• Haematocrit (full blood count): Checked at baseline, at 3–6 months, and then at least annually. Therapy should be paused if haematocrit exceeds 0.54 (54%); investigate and treat the cause, and resume only when safe.

• Prostate monitoring: Digital rectal examination (DRE) and PSA testing in men over 40 years or those at increased prostate cancer risk. PSA should be measured in micrograms per litre (µg/L), the standard UK unit. Follow local laboratory reference ranges and NICE guideline NG12 (Suspected cancer: recognition and referral) for referral thresholds. Refer urgently to urology if there is an abnormal DRE, a persistently rising PSA, or other concerning features.

• Blood pressure and cardiovascular assessment: Monitor blood pressure and assess for symptoms of cardiovascular disease.

• Metabolic profile: Lipid profile and fasting glucose or HbA1c, particularly in men with cardiovascular risk factors or diabetes.

Long-term monitoring (after stabilisation):

Once testosterone levels are stable and symptoms have improved, monitoring frequency can be reduced to:

• Annual testosterone level checks (morning, pre-dose) to ensure levels remain within the therapeutic range

• Annual PSA and prostate assessment (DRE and PSA) in men over 40 years or at increased risk

• Annual full blood count to monitor haematocrit and haemoglobin

• Annual blood pressure and cardiovascular risk assessment

• Periodic lipid profile and glucose/HbA1c as clinically indicated

• Bone density scans (DEXA) if osteoporosis was a presenting feature or if other risk factors are present

Liver function tests are not routinely required for transdermal testosterone but may be checked if there is clinical concern or pre-existing liver disease.

Dose adjustments may be necessary based on testosterone levels and clinical response. If levels remain suboptimal despite good compliance, the dose may be increased (up to the maximum licensed dose as per the Summary of Product Characteristics). Conversely, if testosterone levels are supraphysiological or adverse effects occur (e.g., erythrocytosis, oedema), dose reduction should be considered.

When to refer or seek specialist advice:

• Suspected prostate cancer: Abnormal DRE, persistently rising PSA, or lower urinary tract symptoms (refer urgently per NICE NG12)

• Suspected pituitary disease: Visual field defects, severe persistent headaches, hyperprolactinaemia, or evidence of multiple pituitary hormone deficiencies (refer to endocrinology)

• Persistent symptoms despite adequate testosterone levels: Consider alternative diagnoses or contributing factors

• Haematocrit >0.54: Pause therapy, investigate cause, refer to haematology if needed

• Cardiovascular events or significant risk factors: Liaise with cardiology as appropriate

Treatment review: Testosterone replacement is typically a long-term therapy for men with permanent hypogonadism (e.g., primary testicular failure, pituitary disease). However, in cases of secondary hypogonadism due to potentially reversible causes (such as obesity, certain medications, or acute illness), periodic treatment breaks may be considered under specialist guidance to reassess whether endogenous testosterone production has recovered. Any decision to discontinue treatment should be made in consultation with a specialist, as abrupt cessation can lead to recurrence of hypogonadal symptoms. Patients should maintain regular contact with their healthcare team and report any concerns promptly to ensure safe, effective long-term management.

Frequently Asked Questions