Does Testogel contain Sustanon? No, Testogel does not contain Sustanon. These are two entirely separate testosterone replacement therapy (TRT) products with distinct formulations and delivery methods. Testogel is a transdermal gel applied daily to the skin, containing testosterone as its sole active ingredient. Sustanon, conversely, is an intramuscular injection comprising four different testosterone esters designed for sustained release. Whilst both treat male hypogonadism by restoring testosterone levels, their pharmacokinetic profiles, dosing schedules, and patient suitability differ considerably. Understanding these differences helps patients and clinicians select the most appropriate treatment option based on individual clinical needs, lifestyle factors, and treatment goals.

Understanding Testogel and Sustanon: Key Differences

Testogel does not contain Sustanon. These are two distinct testosterone replacement therapy (TRT) products with fundamentally different formulations, delivery methods, and pharmacokinetic profiles. Understanding these differences is essential for patients and healthcare professionals when selecting the most appropriate treatment option.

Testogel is a transdermal gel containing testosterone as a single active ingredient. It is applied daily to the skin, typically on the shoulders, upper arms, or abdomen, where the hormone is absorbed gradually through the dermal layers into the bloodstream. This topical formulation provides relatively stable serum testosterone concentrations throughout the day, with less pronounced fluctuations than some injectable alternatives.

Sustanon, by contrast, is an intramuscular injection containing a blend of four different testosterone esters: testosterone propionate, testosterone phenylpropionate, testosterone isocaproate, and testosterone decanoate. This combination was specifically designed to provide both immediate and sustained testosterone release following a single injection, typically administered every three weeks (though this may be adjusted according to clinical need). The different ester chain lengths result in varying absorption and elimination rates, creating a complex pharmacokinetic profile.

The confusion between these products may arise because both are licensed testosterone preparations used for male hypogonadism. However, their administration routes, dosing schedules, and patient suitability profiles differ considerably. Testogel offers convenience and non-invasive administration, whilst Sustanon provides longer intervals between doses but requires injection technique and is typically administered by healthcare professionals. The choice between them depends on individual patient factors, lifestyle considerations, and clinical response to treatment.

Active Ingredients in Testogel vs Sustanon

The active pharmaceutical ingredients in these two products are chemically distinct, despite both ultimately delivering testosterone to the body.

Testogel contains testosterone in a 1% gel formulation. In the UK, Testogel is available as 50 mg/5 g gel sachets. The gel vehicle includes excipients such as carbomer 980, isopropyl myristate, ethanol 96%, and purified water. The testosterone molecule in Testogel is unmodified and is absorbed directly through the skin. The prescribed dose is adjusted according to serum testosterone monitoring.

Sustanon 250 contains a proprietary blend of four testosterone esters in each 1 ml ampoule:

• Testosterone propionate 30 mg (short-acting ester)

• Testosterone phenylpropionate 60 mg (short-to-medium acting)

• Testosterone isocaproate 60 mg (medium-acting)

• Testosterone decanoate 100 mg (long-acting ester)

These esters are testosterone molecules with different fatty acid chains attached. Once injected into muscle tissue, enzymes gradually cleave these ester bonds, releasing free testosterone into the circulation at different rates. The propionate ester provides an initial testosterone surge within 24–48 hours, whilst the decanoate ester continues releasing testosterone for up to three weeks.

This fundamental difference in formulation means that whilst both products deliver bioidentical testosterone, the kinetics, dosing frequency, and plasma concentration profiles differ substantially. Testogel provides more stable daily levels, whereas Sustanon produces characteristic peak-and-trough patterns between injections. Neither product contains the other's formulation components.

How Testogel and Sustanon Work in the Body

Both Testogel and Sustanon aim to restore physiological testosterone levels in men with confirmed hypogonadism, but their mechanisms of delivery and pharmacokinetic behaviour differ considerably.

Testogel's mechanism of action begins with dermal application. The alcohol-based gel vehicle facilitates testosterone penetration through the stratum corneum (the skin's outer layer). Once absorbed, testosterone enters the systemic circulation via dermal capillaries, bypassing first-pass hepatic metabolism. This transdermal route produces relatively stable serum testosterone concentrations throughout the 24-hour dosing interval, with peak levels typically occurring 2–4 hours post-application. Daily application maintains steady-state concentrations, with less pronounced fluctuations than injectable formulations. The gel must be allowed to dry completely before dressing, and skin-to-skin contact with others should be avoided for at least 6 hours after application to prevent inadvertent testosterone transfer. If contact is anticipated before this time, the application site should be washed thoroughly with soap and water.

Sustanon's mechanism involves intramuscular depot injection, typically into the gluteal muscle or thigh. The four testosterone esters form an oil-based depot within the muscle tissue. Esterases (enzymes present in blood and tissues) progressively hydrolyse the ester bonds, releasing free testosterone. The rate of hydrolysis depends on ester chain length: shorter esters (propionate) are cleaved rapidly, producing an early testosterone peak, whilst longer esters (decanoate) provide sustained release over weeks. This results in supraphysiological testosterone levels shortly after injection, followed by gradual decline until the next dose.

Once in circulation, testosterone from either source binds to sex hormone-binding globulin (SHBG) and albumin, with approximately 2% remaining as free, biologically active hormone. Testosterone exerts its effects by binding to androgen receptors in target tissues (muscle, bone, brain, reproductive organs), promoting protein synthesis, erythropoiesis, libido, and secondary sexual characteristics. Both formulations undergo similar metabolism, primarily in the liver, converting to dihydrotestosterone (DHT) and oestradiol via 5α-reductase and aromatase enzymes respectively.

Choosing Between Testogel and Sustanon for TRT

The selection between Testogel and Sustanon for testosterone replacement therapy should be individualised, considering clinical factors, patient preference, lifestyle, and treatment goals. UK guidance from NICE Clinical Knowledge Summaries (CKS) and the British Society for Sexual Medicine (BSSM) emphasises shared decision-making and regular monitoring regardless of formulation chosen.

Testogel may be preferred when:

• Convenience and non-invasive administration are priorities—many patients prefer avoiding injections

• Stable testosterone levels are clinically desirable, particularly in men sensitive to hormonal fluctuations

• Needle phobia or coagulation disorders make injections problematic

• Flexibility in dose adjustment is needed—gel doses can be titrated more readily than injection intervals

• Patients can reliably apply the gel daily and observe transfer precautions (particularly important for those with partners or children)

Sustanon may be preferred when:

• Adherence concerns exist with daily topical therapy—three-weekly injections may improve compliance

• Cost considerations are relevant—according to the BNF, injectable testosterone is generally less expensive than transdermal preparations in the UK

• Skin conditions or reactions preclude topical application

• Patients prefer less frequent dosing despite the injection requirement

• There are concerns about testosterone transfer risk to household contacts

Clinical monitoring is essential with both treatments. Baseline investigations should include serum testosterone (measured between 8–10 am), full blood count, prostate-specific antigen (PSA) in men at risk of prostate cancer, and liver function tests. Follow-up testosterone levels should be checked at 3 months, then 6–12 monthly once stable. For Testogel, blood sampling should occur 2–6 hours post-application; for Sustanon, trough levels (just before the next injection is due) are most informative.

True contraindications include known or suspected prostate or breast cancer. Cautions include cardiac impairment, epilepsy, migraine, sleep apnoea, and pre-existing polycythaemia. Some patients may trial one formulation and switch to another based on tolerability, efficacy, or lifestyle changes. Regular review with a GP or endocrinologist ensures optimal therapeutic outcomes and safety monitoring.

Safety and Side Effects: Comparing Both Treatments

Both Testogel and Sustanon carry similar systemic side effects related to testosterone therapy itself, but differ in administration-related adverse events and monitoring requirements.

Common side effects shared by both treatments include:

• Polycythaemia (increased red blood cell production)—requires regular full blood count monitoring; haematocrit >0.54 may necessitate dose reduction or temporary cessation

• Prostate effects—benign prostatic hyperplasia symptoms may worsen; PSA elevation requires investigation

• Mood and behavioural changes—irritability, aggression, or mood swings, particularly with fluctuating levels

• Acne and oily skin—due to increased sebaceous gland activity

• Gynaecomastia—breast tissue development from testosterone aromatisation to oestradiol

• Fluid retention and oedema—particularly in those with cardiac or renal impairment

• Sleep apnoea—testosterone may worsen existing obstructive sleep apnoea

• Reduced fertility—exogenous testosterone suppresses gonadotrophin secretion, reducing spermatogenesis

• Venous thromboembolism—testosterone therapy may increase risk of blood clots

Testogel-specific considerations:

• Skin reactions—application site irritation, erythema, or allergic contact dermatitis occur in approximately 5–7% of users

• Transfer risk—inadvertent testosterone exposure to partners or children through skin contact is a significant concern; patients must wash hands thoroughly after application and cover application sites with clothing for at least 6 hours

• Application site variability—absorption can vary with skin condition, temperature, and application technique

Sustanon-specific considerations:

• Injection site reactions—pain, swelling, or abscess formation at injection sites

• Peak-trough fluctuations—some men experience mood swings, energy fluctuations, or libido changes corresponding to the injection cycle

• Supraphysiological peaks—testosterone levels may exceed normal range shortly after injection

When to seek medical advice:

Patients should contact their GP urgently if they experience chest pain, shortness of breath, leg swelling or pain (possible DVT), severe headaches, visual disturbances, or signs of allergic reaction. Routine monitoring appointments should not be missed, as serious complications like polycythaemia or prostate abnormalities may be asymptomatic initially.

The MHRA advises that testosterone therapy should only continue if clinical and biochemical hypogonadism is confirmed, and benefits outweigh risks on ongoing assessment. Patients should report any suspected side effects via the MHRA Yellow Card Scheme.

Frequently Asked Questions