Can I have Nebido and Testogel together? This is a common question amongst men receiving testosterone replacement therapy (TRT) for hypogonadism. Nebido (testosterone undecanoate injection) and Testogel (testosterone gel) are both licensed testosterone preparations used to restore normal testosterone levels in men with confirmed deficiency. However, combining these two formulations is not recommended in routine clinical practice. Using both simultaneously would typically result in excessive testosterone dosing, increasing the risk of serious adverse effects such as polycythaemia, cardiovascular complications, and suppression of natural hormone production, without providing additional therapeutic benefit. This article explains why these treatments should not be combined and what safe alternatives exist if your current therapy is not working effectively.

Can You Use Nebido and Testogel Together?

In general, Nebido and Testogel are not recommended to be used together. Both are testosterone replacement therapies (TRT) prescribed for male hypogonadism—a condition where the body does not produce sufficient testosterone. Using both preparations simultaneously would typically result in an excessive total dose of testosterone, increasing the risk of adverse effects without providing additional clinical benefit.

Nebido (testosterone undecanoate) is a long-acting intramuscular injection administered every 10–14 weeks after an initial loading regimen, whilst Testogel (testosterone gel) is a topical preparation applied daily to the skin. Each is designed to restore testosterone levels to the normal physiological range when used alone. Combining them would generally lead to supraphysiological testosterone levels, which can cause serious side effects.

There is no standard clinical indication for routinely combining these two testosterone formulations. The British Society for Sexual Medicine (BSSM) guidelines and NICE Clinical Knowledge Summary recommend using a single testosterone preparation at the appropriate dose, with regular monitoring of serum testosterone levels and haematocrit. If your current treatment is not achieving adequate symptom control or testosterone levels, your doctor should adjust the dose or consider switching to an alternative formulation rather than adding a second testosterone product.

Before starting any testosterone therapy, you should have had two separate morning blood tests confirming low testosterone with associated symptoms, and appropriate investigations including LH/FSH levels. Testosterone therapy is contraindicated in men with prostate or breast cancer, haematocrit >0.54, severe cardiac, hepatic or renal failure, or untreated sleep apnoea.

If you are considering changes to your testosterone replacement therapy, it is essential to discuss this with your GP or endocrinologist. Never combine or alter testosterone treatments without medical supervision, as this can lead to significant health risks.

How Nebido and Testogel Work in Testosterone Replacement

Nebido and Testogel both deliver exogenous testosterone but through different routes and with distinct pharmacokinetic profiles. Understanding how each works helps explain why combining them is unnecessary and potentially harmful.

Nebido (testosterone undecanoate injection) is administered as a deep intramuscular injection, typically into the gluteal muscle. The testosterone undecanoate ester is slowly released from the injection depot and hydrolysed to release free testosterone into the bloodstream. This formulation follows a loading schedule with the second injection at 6 weeks after the first, then maintenance injections every 10–14 weeks. Peak levels occur within the first few days after injection followed by a gradual decline. The long duration of action makes Nebido convenient, requiring only 3-4 injections per year once steady state is achieved.

Testogel is available in the UK as either 50 mg sachets (1% gel) or as a 16.2 mg/g pump dispenser. It is applied daily to clean, dry skin on the shoulders, upper arms, or abdomen. The testosterone is absorbed transdermally and enters the systemic circulation, bypassing first-pass hepatic metabolism. Steady-state testosterone levels are typically achieved within a few days of starting treatment. The daily application allows for dose flexibility and can be discontinued quickly if adverse effects occur.

Both preparations aim to restore serum testosterone to the normal adult male range (as defined by your local laboratory reference range). When used correctly as monotherapy, each formulation is effective at relieving hypogonadal symptoms such as reduced libido, erectile dysfunction, fatigue, reduced muscle mass, and mood disturbances. Regular monitoring through blood tests ensures testosterone levels remain within the therapeutic window—morning pre-dose levels for Testogel, and trough levels (just before the next injection) for Nebido.

Why Combining Two Testosterone Treatments Is Not Recommended

Combining Nebido and Testogel would result in testosterone overdose, leading to potentially serious adverse effects. The primary concern is achieving supraphysiological testosterone levels—concentrations significantly above the normal physiological range—which offers no additional clinical benefit but substantially increases health risks.

Key risks of excessive testosterone include:

• Polycythaemia and erythrocytosis: Testosterone stimulates red blood cell production. Elevated haematocrit (>0.54) increases blood viscosity, raising the risk of thrombotic events including stroke, myocardial infarction, and venous thromboembolism. Regular full blood count monitoring is essential during TRT, and combining preparations would accelerate this risk.

• Cardiovascular considerations: The MHRA has stated that the evidence for increased cardiovascular risk with licensed testosterone use is not conclusive. However, supraphysiological testosterone levels may adversely affect lipid profiles, blood pressure, and endothelial function, potentially increasing risk.

• Suppression of spermatogenesis: High-dose testosterone suppresses the hypothalamic-pituitary-gonadal axis, reducing luteinising hormone (LH) and follicle-stimulating hormone (FSH) secretion. This can lead to testicular atrophy and infertility—a particular concern for men of reproductive age.

• Mood and behavioural changes: Supraphysiological levels may cause irritability, aggression, mood swings, and sleep disturbances.

Nebido injections specifically carry a risk of pulmonary oil microembolism (POME), which can cause symptoms like cough, shortness of breath, chest pain, dizziness, or flushing immediately after injection. These require urgent medical attention.

The MHRA and prescribing guidelines emphasise individualised dosing with a single testosterone preparation. If symptom control is inadequate, the appropriate response is dose optimisation or formulation change—not adding a second testosterone product. Your healthcare provider should conduct regular monitoring including testosterone levels, haematocrit, prostate-specific antigen (PSA), and clinical assessment. If you experience side effects, report them to your doctor and consider using the MHRA Yellow Card scheme.

When Your Doctor Might Switch Between Nebido and Testogel

Switching between testosterone formulations is a recognised clinical practice when the current preparation is not meeting treatment goals or causing tolerability issues. Your doctor may consider changing from Nebido to Testogel, or vice versa, in several circumstances.

Reasons for switching from Nebido to Testogel:

• Injection-related problems: Some patients experience pain, anxiety, or local reactions at injection sites. Needle phobia or difficulty attending clinic appointments every 10–14 weeks may make daily gel application more practical.

• Fluctuating testosterone levels: Whilst Nebido generally provides stable levels, some men experience symptomatic decline towards the end of the dosing interval ("trough symptoms"). Testogel's daily administration may provide more consistent levels.

• Adverse effects: If polycythaemia develops on Nebido, switching to a formulation with more flexible dosing may help manage haematocrit levels.

Reasons for switching from Testogel to Nebido:

• Poor adherence: Daily gel application requires consistent compliance. Men who struggle with daily medication may benefit from quarterly injections.

• Skin reactions: Testogel can cause local irritation, dryness, or allergic contact dermatitis in some users.

• Transfer concerns: There is a risk of testosterone transfer to partners or children through skin contact. Nebido eliminates this concern.

• Inadequate absorption: Some patients have suboptimal transdermal absorption, resulting in persistently low testosterone levels despite appropriate gel dosing.

The switching process requires careful planning. When transitioning between formulations, your doctor will follow the appropriate loading schedule for Nebido (injections at 0 and 6 weeks, then maintenance) or initiate Testogel according to the product guidelines. Any overlap period should only occur under specialist supervision with close monitoring of testosterone levels and haematocrit.

If using Testogel during any transition period, remember to apply it to clean, dry skin, allow it to dry completely, wash your hands thoroughly afterwards, and cover the application site with clothing to prevent transfer to others. Never attempt to switch formulations or combine treatments without medical supervision.

Safe Alternatives If Your Current Testosterone Treatment Isn't Working

If your current testosterone replacement therapy is not adequately controlling symptoms or achieving target testosterone levels, several evidence-based alternatives exist beyond simply adding another testosterone product.

Dose optimisation is the first-line approach. For Testogel 16.2 mg/g pump, doses can be adjusted between 20.25 mg and 81 mg daily. For Testogel 50 mg sachets, the dose can be adjusted to 50-100 mg daily. For Nebido, injection frequency can be modified—some men benefit from injections every 10 weeks rather than 12–14 weeks if trough symptoms occur. Your doctor will use blood test results (trough levels just before the next injection for Nebido, or morning pre-dose levels for Testogel) to guide dose adjustments.

Alternative testosterone formulations available in the UK include:

• Tostran 2% gel: A different transdermal gel with a metered-dose pump for precise dosing

• Testim gel: An alternative transdermal gel with different absorption characteristics

• Sustanon injections: A shorter-acting testosterone ester blend requiring injections every 2–3 weeks

• Testosterone enantate: Another short-acting injectable option

Addressing underlying factors is crucial. Poor response to TRT may indicate:

• Incorrect diagnosis: Symptoms attributed to low testosterone may have other causes (thyroid disorders, depression, sleep apnoea, diabetes)

• Suboptimal administration: Testogel applied to incorrect sites or at wrong times; injection technique issues

• Concurrent medications: Some drugs may interfere with testosterone metabolism

• Lifestyle factors: Obesity, excessive alcohol, poor sleep, and lack of exercise can impair treatment response

When to contact your GP or endocrinologist:

• Persistent symptoms despite treatment

• Side effects from current therapy, including haematocrit >0.54 (may require dose reduction or venesection)

• Difficulty adhering to your treatment regimen

• Concerns about fertility

• New symptoms such as chest pain, severe headaches, or leg swelling

NICE recommends specialist referral if primary care management is unsuccessful or if there are complex issues such as fertility concerns, pituitary disorders, or unclear diagnosis. Never self-adjust testosterone doses or combine formulations—always discuss treatment changes with your healthcare provider to ensure safe, effective therapy tailored to your individual needs.

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