Is Testogel or injection better for testosterone replacement therapy (TRT)? Both transdermal testosterone gel (such as Testogel) and intramuscular testosterone injections (such as Sustanon 250 or Nebido) are effective, evidence-based treatments for men with confirmed hypogonadism. Neither option is universally superior—the choice depends on individual patient factors including lifestyle, preference for administration route, tolerance of side effects, and practical considerations. This article examines how each treatment works, compares their effectiveness and safety profiles, and explores practical factors to help you and your clinician make an informed, personalised decision about testosterone replacement therapy.

Understanding Testosterone Replacement Therapy Options

Testosterone replacement therapy (TRT) is prescribed for men diagnosed with hypogonadism—a condition where the testes produce insufficient testosterone. According to NICE Clinical Knowledge Summaries (CKS), TRT should only be initiated following confirmed biochemical testosterone deficiency (two fasting morning samples, ideally taken before 11am, showing low total testosterone) alongside relevant clinical symptoms such as reduced libido, erectile dysfunction, fatigue, or loss of muscle mass.

Diagnosis requires careful assessment. Blood tests should include luteinising hormone (LH), follicle-stimulating hormone (FSH), and sex hormone-binding globulin (SHBG) to calculate free testosterone if total testosterone is borderline. Men with symptoms suggesting pituitary disease—such as headache, visual disturbance, or galactorrhoea—or those with low or inappropriately normal LH/FSH alongside low testosterone require urgent specialist referral to endocrinology. TRT is indicated for confirmed pathological hypogonadism, not routinely for age-related decline in testosterone.

In the UK, the two most commonly prescribed forms of TRT are transdermal testosterone gel (such as Testogel) and intramuscular testosterone injections (such as Sustanon 250, testosterone enantate, or long-acting testosterone undecanoate [Nebido]). Both aim to restore testosterone levels to the normal physiological range, thereby alleviating symptoms of deficiency. However, they differ significantly in their delivery method, pharmacokinetics, and practical implications for daily life.

The choice between gel and injections is not simply a matter of clinical superiority—both are effective when used appropriately. Instead, the decision often depends on individual patient factors including lifestyle, preference for administration route, tolerance of side effects, fertility plans, and the ability to maintain consistent treatment adherence. Understanding how each option works, their respective benefits and drawbacks, and practical considerations can help patients and clinicians make an informed, personalised treatment decision.

It is essential that TRT is prescribed and monitored by a qualified healthcare professional, typically an endocrinologist or specialist with experience in male hypogonadism. Men wishing to father children should avoid TRT, as it suppresses natural sperm production; they should be referred to andrology or endocrinology to discuss alternative treatments such as gonadotrophins.

How Testogel and Testosterone Injections Work

Testogel is a transdermal gel containing testosterone, typically applied once daily to clean, dry skin. In the UK, common formulations include Testogel 16.2 mg/g gel (supplied in a pump dispenser) and Testogel 1% (50 mg testosterone in 5 g gel, supplied in sachets). Application sites differ by product: Testogel 16.2 mg/g should be applied to the shoulders and upper arms only, whilst Testogel 1% may be applied to the shoulders, upper arms, or abdomen. The gel must never be applied to the genital area. Testosterone is absorbed through the skin into the bloodstream over several hours, providing a relatively steady release throughout the day.

The gel's pharmacokinetic profile aims to mimic the body's natural diurnal testosterone rhythm, with levels peaking a few hours after application and gradually declining. Patients must allow the gel to dry completely (typically 3–5 minutes) before dressing. The gel is flammable until dry, so avoid smoking or going near naked flames during this time. To prevent inadvertent transfer to others—particularly women and children, which can cause virilisation (including genital enlargement, premature puberty, aggressive behaviour, and advanced bone age)—patients should wash their hands immediately after application, cover application sites with clothing once dry, and wash the application area before any anticipated close skin-to-skin contact. If accidental contact occurs, the exposed skin of the other person should be washed with soap and water as soon as possible.

Testosterone injections deliver a depot formulation of testosterone directly into the muscle (usually the gluteal or thigh muscle). In the UK, Sustanon 250 or testosterone enantate are typically administered every 2–3 weeks, whilst longer-acting testosterone undecanoate (Nebido) is given every 10–14 weeks after an initial loading phase. Nebido should be administered by a trained healthcare professional in a clinical setting due to the large injection volume and the risk of pulmonary oil microembolism (POME) and anaphylaxis; patients should be observed for at least 30 minutes after each injection. Shorter-acting injections may be administered by a healthcare professional or, with appropriate training, self-administered at home by the patient.

Injections produce an initial peak in testosterone levels shortly after administration, followed by a gradual decline until the next dose. This creates more pronounced fluctuation in serum testosterone compared to daily gel application. Longer intervals between doses with undecanoate formulations can reduce this variability, though some fluctuation remains inherent to the injection route.

Comparing Effectiveness: Testogel vs Injections

Both Testogel and testosterone injections are clinically effective at restoring testosterone levels and improving symptoms of hypogonadism when used correctly. Clinical trials and systematic reviews have demonstrated that both modalities can successfully normalise serum testosterone, improve sexual function, increase muscle mass and strength, enhance mood and energy levels, and improve bone mineral density over time. Direct head-to-head evidence comparing different TRT formulations is limited, but available data suggest no significant differences in efficacy for improving hypogonadal symptoms when testosterone levels are adequately restored.

The effectiveness of Testogel depends significantly on consistent daily application and adequate skin absorption. Individual variation in skin permeability, application technique, and adherence can affect therapeutic outcomes. Some patients may require dose adjustments to achieve target testosterone levels. Regular monitoring is essential to ensure adequate replacement, with serum testosterone typically measured 2–4 hours after gel application once steady state is reached (usually after one week of treatment). The aim is to achieve mid-normal serum testosterone levels (approximately 15–25 nmol/L, individualised to the patient).

Testosterone injections provide more predictable pharmacokinetics in terms of total dose delivered, as the entire administered amount enters the systemic circulation. However, the fluctuating levels between injections can result in corresponding symptom variation—some men report feeling energetic shortly after injection but experience declining energy and mood as levels drop before the next dose. Longer-acting formulations like testosterone undecanoate provide more stable levels and may reduce this "peak and trough" effect. For injections, serum testosterone is typically measured at trough (immediately before the next dose) to ensure levels remain within the target range.

The choice should be individualised based on patient preference, tolerability, and practical considerations rather than assumed superiority of one delivery method over another. Treatment can be switched if the initial choice proves unsuitable, with ongoing monitoring of testosterone levels, symptom response, and side effects allowing for treatment optimisation.

Side Effects and Safety Considerations

Both Testogel and testosterone injections carry similar systemic risks associated with testosterone replacement, as outlined by the MHRA and product summaries of product characteristics (SmPCs). These include polycythaemia (increased red blood cell production), which can increase cardiovascular and thromboembolic risk; potential worsening of obstructive sleep apnoea; acne and oily skin; breast tenderness or gynaecomastia; testicular atrophy; and suppression of spermatogenesis, leading to reduced or absent fertility.

Regular monitoring is essential for all patients on TRT. According to NICE CKS and product guidance, monitoring should include serum testosterone levels, full blood count (haematocrit/haemoglobin), and prostate assessment (digital rectal examination and prostate-specific antigen [PSA] in men over 40 or those at higher risk). Blood tests are typically performed at 3–6 months after initiation or dose change, then at least annually, with timing tailored to the formulation used. If haematocrit rises above 54%, consider withholding TRT, investigating the cause, and seeking specialist advice; venesection may be required. Additional monitoring (such as liver function tests or lipid profiles) may be appropriate in men with relevant comorbidities or cardiovascular risk factors. TRT is contraindicated in men with prostate or breast cancer.

Testogel-specific considerations include the risk of transfer to others through skin contact, which can cause virilisation in women and children. Patients must take strict precautions as described above. Local skin reactions—including irritation, redness, or allergic contact dermatitis—occur in approximately 5–10% of users and may necessitate switching to an alternative formulation or delivery method.

Injection-specific side effects include local reactions at the injection site such as pain, swelling, bruising, or rarely abscess formation. With testosterone undecanoate (Nebido), there is a risk of pulmonary oil microembolism (POME) and anaphylaxis; symptoms may include cough, shortness of breath, chest tightness, dizziness, or throat tightening during or immediately after injection. This is why Nebido must be administered by a healthcare professional with appropriate observation. The pronounced fluctuations in testosterone levels with shorter-acting injections may cause mood swings, irritability, or aggression in some individuals.

When to seek urgent medical attention: Call 999 or go to A&E immediately if you experience severe chest pain, sudden shortness of breath, unilateral leg swelling or pain, sudden visual loss, or signs of a severe allergic reaction (such as facial swelling, difficulty breathing, or widespread rash). For persistent but less urgent side effects—such as troublesome acne, mood changes, or inadequate symptom improvement—contact your GP or specialist.

Patients are encouraged to report suspected side effects via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or via the Yellow Card app.

Practical Factors: Convenience, Cost and Lifestyle

Convenience and lifestyle compatibility often significantly influence treatment choice. Testogel requires daily application, which some men find burdensome or difficult to remember consistently. However, it offers flexibility and can be easily adjusted or discontinued if needed. The requirement to avoid skin contact with others for several hours after application, and to wash before close contact, can be problematic for men with young children or intimate partners, and may affect spontaneity in relationships.

Testosterone injections eliminate the need for daily administration, with intervals ranging from 2–3 weeks (Sustanon 250, testosterone enantate) to 10–14 weeks (Nebido). This can be more convenient for men who prefer less frequent treatment. However, injections require either regular clinic visits (particularly for Nebido) or confidence in self-administration technique for shorter-acting preparations. Some men experience anxiety about needles or find intramuscular injection uncomfortable or impractical.

Cost considerations within the NHS are generally not a direct concern for patients, as both treatments are available on prescription when clinically indicated. From a healthcare system perspective, costs vary by formulation, frequency, and whether administration requires healthcare professional time. Private prescription costs vary widely by provider and formulation; patients should discuss costs with their prescribing clinician or pharmacy.

Adherence patterns may differ between formulations. Some studies suggest that adherence to daily gel application may decline over time, particularly in younger men or those with busy lifestyles, though individual variation is considerable. Conversely, scheduled injections—especially when administered by healthcare professionals—may promote better long-term adherence for some patients. However, others prefer the autonomy and control offered by daily gel application.

Travel and work schedules may also influence choice. Men who travel frequently may find carrying gel more convenient than arranging injections abroad, though airport security and customs regulations should be considered; carrying a letter from your prescriber is advisable. Shift workers or those with irregular schedules might find daily gel application challenging to maintain consistently. Men in certain occupations or sports may need to provide documentation to comply with anti-doping regulations; discuss this with your prescribing clinician if relevant.

Which Testosterone Treatment Is Right for You?

The decision between Testogel and testosterone injections should be made collaboratively between patient and clinician, taking into account individual circumstances, preferences, clinical factors, and fertility plans. Neither option is universally "better"—both are effective, evidence-based treatments when used appropriately.

Testogel may be more suitable for men who prefer daily self-administration, want to avoid needles, desire more stable testosterone levels throughout the day, or need flexibility to adjust or stop treatment quickly. It may also be preferred by those who can reliably apply the gel at the same time daily and can manage the skin contact precautions effectively.

Testosterone injections may be preferable for men who struggle with daily adherence, prefer less frequent administration, have concerns about gel transfer to family members, or have skin conditions that might affect gel absorption or cause local reactions. Longer-acting formulations like testosterone undecanoate (Nebido) are particularly suitable for those seeking minimal treatment burden and more stable levels over extended periods, provided they can attend clinic for administration and observation.

Clinical factors should also inform the decision. Men with significant skin conditions, allergies to gel components, or those who cannot reliably avoid skin-to-skin contact may be better suited to injections. Conversely, those with needle phobia, bleeding disorders, or difficulty accessing healthcare facilities for regular injections might prefer gel. Men who are planning to father children should not start TRT, as it suppresses natural sperm production; they should be referred to andrology or endocrinology to discuss fertility-preserving alternatives.

It is important to recognise that treatment can be switched if the initial choice proves unsuitable. Regular follow-up is essential, including symptom review and blood tests at 3–6 months after initiation or dose changes, then at least annually (or more frequently as clinically indicated), with timing tailored to the formulation used. The aim is to achieve mid-normal serum testosterone levels (approximately 15–25 nmol/L, individualised) whilst monitoring for side effects and ensuring symptom improvement. Patients should discuss any concerns about their current treatment with their prescribing clinician rather than discontinuing therapy independently.

When to seek medical advice: Contact your GP or specialist if you experience inadequate symptom improvement after 3–6 months of treatment, troublesome side effects, signs of polycythaemia (such as persistent headaches, dizziness, or visual disturbances), new or worsening urinary symptoms, or significant mood changes. Call 999 or go to A&E immediately for severe chest pain, sudden shortness of breath, unilateral leg swelling, or sudden visual loss. Regular monitoring as recommended by your healthcare team is essential for safe, effective long-term testosterone replacement therapy.

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