Many men wonder whether testosterone treatment can increase penis size, particularly if they are concerned about their dimensions or experiencing symptoms of low testosterone. Testosterone is essential for penile development during specific life stages—foetal development and puberty—but its role in adult penile size is often misunderstood. Once puberty is complete, the penis has typically reached its adult dimensions, and additional testosterone does not stimulate further growth. This article examines the evidence surrounding testosterone and penile size, explains when testosterone treatment is medically appropriate, and provides guidance on speaking to your GP about concerns.

Understanding Testosterone and Penile Development

Testosterone is the primary male sex hormone (androgen) responsible for the development of male sexual characteristics during puberty. Produced predominantly in the testes, testosterone plays a crucial role in penile growth during specific developmental windows—primarily during foetal development and throughout puberty.

During foetal development, testosterone exposure between weeks 8 and 24 of gestation is essential for the formation of male external genitalia. Subsequently, during puberty (typically between ages 10 and 16), rising testosterone levels trigger significant penile growth alongside other secondary sexual characteristics such as increased muscle mass, deepening of the voice, and facial hair development. The majority of penile growth occurs during this pubertal window, with most males reaching adult penile size by late adolescence, though some individuals may continue development into their late teens.

Once puberty is complete, the penis has typically reached its adult dimensions. At this stage, the body's natural testosterone levels maintain sexual function, libido, and general male characteristics, but they do not stimulate further penile growth. The relationship between testosterone and penile size is therefore time-dependent and confined to specific developmental periods.

It is important to understand that normal adult testosterone levels vary considerably between individuals (typically 8–30 nmol/L, though ranges vary by laboratory and assay method), and these variations do not correlate with penile size in adults. Men with testosterone levels within the normal range will not experience penile growth from additional testosterone supplementation, as the developmental window for such growth has closed.

A true micropenis (stretched penile length more than 2.5 standard deviations below the mean for age) is rare and requires early assessment by a paediatric endocrinologist or urologist.

Can Testosterone Treatment Increase Penis Size in Adults?

There is no clinical evidence that testosterone treatment increases penis size in adult men with normal testosterone levels. Once puberty is complete, the penis does not respond to testosterone with further growth. Testosterone replacement therapy (TRT) is a legitimate medical treatment prescribed for confirmed hypogonadism—a condition where the body produces insufficient testosterone—but penile enlargement is not an expected or documented outcome in adults.

Testosterone replacement therapy, when clinically indicated, can improve symptoms associated with low testosterone such as reduced libido, erectile dysfunction, fatigue, decreased muscle mass, and mood disturbances. The Medicines and Healthcare products Regulatory Agency (MHRA) has approved various testosterone formulations (gels, injections, patches) specifically for treating hypogonadism, not for cosmetic or enhancement purposes.

In rare cases involving delayed puberty or specific endocrine disorders, testosterone treatment administered during adolescence may support normal penile development if puberty has not yet completed. However, this requires specialist paediatric endocrinology assessment and is entirely different from adult testosterone use. Such treatment must be carefully monitored and is only appropriate when genuine hormonal deficiency is confirmed through blood tests and clinical evaluation.

Using testosterone without medical indication carries significant risks, including:

• Possible cardiovascular effects (caution is advised in men with pre-existing cardiovascular disease)

• Suppression of natural testosterone production and fertility (can markedly reduce sperm production)

• Worsening of lower urinary tract symptoms due to prostate enlargement

• Mood disturbances and psychological effects

• Testicular atrophy

• Polycythaemia (excessive red blood cell production)

• Acne, oedema, gynaecomastia, and sleep apnoea exacerbation

Testosterone is contraindicated in men with known or suspected prostate or breast cancer. Treatment requires regular monitoring of blood counts, PSA (prostate-specific antigen), blood pressure, and liver function.

The European Medicines Agency (EMA) and MHRA emphasise that testosterone therapy should only be used when testosterone deficiency has been confirmed by clinical signs and biochemical tests, not for age-related decline without confirmed hypogonadism.

If you experience side effects from prescribed testosterone, report them through the MHRA Yellow Card scheme.

Evidence-Based Alternatives for Size Concerns

Concerns about penile size are common, yet research consistently shows that most men who worry about their size actually fall within the normal range. A comprehensive systematic review published in the British Journal of Urology International found that the average erect penis length is approximately 13.12 cm (5.16 inches), with considerable natural variation. Perceived inadequacy often stems from unrealistic comparisons rather than genuine medical concerns.

Most products marketed for penile enlargement—including pills, creams, and supplements—lack robust clinical evidence and are not regulated as medicines by the MHRA. Many such products may contain undeclared ingredients or make unsubstantiated claims.

Penile traction devices (which should have UKCA or CE marking if properly regulated) have limited evidence for modest increases in length (typically 1-2 cm after months of consistent use), but are not routinely recommended for cosmetic purposes and should only be used following specialist advice. Vacuum devices may temporarily increase size but do not create permanent changes.

For men experiencing genuine distress about penile size (a condition sometimes termed "penile dysmorphic disorder" or small penis anxiety), psychological support is the most evidence-based intervention. Cognitive behavioural therapy (CBT) has demonstrated effectiveness in addressing body image concerns and can be accessed through NHS Talking Therapies services or via GP referral.

Surgical options for penile lengthening or girth enhancement do exist but are rarely recommended due to:

• Limited effectiveness (typically 1–2 cm gain at most)

• Significant complication rates (scarring, deformity, erectile dysfunction)

• High dissatisfaction rates post-procedure

• Lack of NHS funding (considered cosmetic)

The British Association of Urological Surgeons advises extreme caution regarding penile enhancement procedures and emphasises that such interventions should only be considered in exceptional circumstances with full informed consent regarding risks and realistic outcomes.

If you have a medical condition affecting penile appearance or function, such as Peyronie's disease (penile curvature) or buried penis due to obesity, speak to your GP about appropriate referral to urology services.

Speaking to Your GP About Testosterone Treatment

If you are considering testosterone treatment for any reason, the first step is an honest conversation with your GP. Your doctor can assess whether you have genuine symptoms of testosterone deficiency and arrange appropriate investigations. It is important to be open about your concerns and motivations, as this allows your GP to provide tailored advice and address any misconceptions.

Your GP will typically:

• Take a detailed medical history, including symptoms such as reduced libido, erectile difficulties, fatigue, mood changes, or reduced muscle mass

• Arrange blood tests to measure testosterone levels (taken in the morning between 7-11am when levels are highest, and repeated to confirm results)

• Assess for underlying causes of low testosterone, such as obesity, diabetes, or pituitary disorders

• Discuss realistic expectations of any treatment

According to UK clinical guidance, testosterone replacement is generally considered when testosterone levels are below 8 nmol/L with symptoms. For borderline levels (8-12 nmol/L), treatment may be considered if symptoms are present and free testosterone is low. Additional tests including luteinising hormone (LH), follicle-stimulating hormone (FSH), prolactin, and sex hormone binding globulin (SHBG) help determine the cause of low testosterone.

Referral to an endocrinologist is appropriate if secondary hypogonadism is suspected (low testosterone with normal or low LH/FSH), particularly with symptoms such as headaches, visual disturbances, or high prolactin levels that might suggest pituitary disease. Referral to urology may be appropriate for primary testicular disorders or fertility concerns.

If testosterone treatment is initiated, regular monitoring is essential, including:

• Blood counts (haematocrit)

• PSA and prostate examination (in men over 40)

• Blood pressure

• Lipid profile and liver function tests

Your GP can also provide reassurance if your concerns about penile size are unfounded or refer you to appropriate psychological support services if body image concerns are affecting your quality of life. If erectile dysfunction is a concern, your GP can explore evidence-based treatments such as phosphodiesterase-5 inhibitors (e.g., sildenafil) or investigate underlying causes.

Never obtain testosterone from unregulated sources such as online suppliers or gyms. Unregulated testosterone products may be counterfeit, contaminated, or incorrectly dosed, and using them without medical supervision poses serious health risks. If you have concerns about sexual health, size, or hormone levels, your GP is your safest and most reliable first point of contact.

Frequently Asked Questions