Testosterone replacement therapy (TRT) is prescribed to men with clinically confirmed hypogonadism to restore hormone levels and improve symptoms such as low libido and fatigue. Whilst TRT can enhance sexual function, many men wonder whether testosterone treatment affects ejaculation. The physical act of ejaculation typically remains intact during treatment, though the composition of seminal fluid—particularly sperm count—is often significantly reduced. Understanding how testosterone therapy influences both ejaculatory function and fertility is essential for informed decision-making. This article explores the mechanisms behind these effects, potential side effects, and when to seek medical advice.

How Testosterone Treatment Works in the Body

Testosterone replacement therapy (TRT) is prescribed to men with clinically confirmed hypogonadism—a condition where the testes produce insufficient testosterone. Diagnosis typically requires two separate early-morning blood tests showing low testosterone levels, along with assessment of luteinising hormone (LH) and follicle-stimulating hormone (FSH) to identify the underlying cause.

Treatment aims to restore testosterone to the mid-normal physiological range, with target levels individualised based on symptoms and clinical response. In the UK, testosterone can be administered through several routes: intramuscular injections (typically testosterone undecanoate given every 10–14 weeks after an initial 6-week loading dose, or shorter-acting preparations), or transdermal gels applied daily to the skin. Oral testosterone undecanoate and subcutaneous pellets are not routinely available or commissioned in NHS practice.

Once absorbed, exogenous testosterone binds to androgen receptors throughout the body, influencing multiple physiological systems. It supports muscle mass maintenance, bone density, red blood cell production, mood regulation, and sexual function. However, the introduction of external testosterone creates a negative feedback loop within the hypothalamic-pituitary-gonadal (HPG) axis.

When the brain detects adequate testosterone levels, it reduces production of luteinising hormone (LH) and follicle-stimulating hormone (FSH)—two hormones essential for natural testosterone production and sperm development within the testes. This suppression is the mechanism by which testosterone treatment can affect reproductive function, including both sperm production and potentially ejaculatory characteristics.

TRT is contraindicated in men with known or suspected prostate or breast cancer, high haematocrit (red blood cell concentration), severe untreated obstructive sleep apnoea, or severe cardiac, hepatic or renal insufficiency. Regular monitoring of testosterone levels, full blood count, liver function, and prostate-specific antigen (PSA) is essential during treatment.

Effects on Sperm Production and Fertility

Testosterone replacement therapy commonly impacts male fertility through its suppressive effect on the HPG axis. When exogenous testosterone is administered, the resulting decrease in LH and FSH leads to reduced or absent sperm production (oligospermia or azoospermia) in most men. Clinical studies indicate that a significant proportion of men on TRT experience substantial reductions in sperm count, potentially affecting fertility during treatment.

This effect typically develops within 3–6 months of starting therapy and is generally reversible upon discontinuation, though recovery timelines vary considerably between individuals. Some men may regain normal sperm production within 6–12 months of stopping treatment, whilst others require longer periods. A small proportion may experience persistent suppression, particularly those with pre-existing fertility issues or after prolonged treatment duration.

Regarding ejaculation specifically, the physical process of ejaculation usually remains intact during testosterone treatment. Most men maintain ejaculatory function, though individual variations in ejaculate volume and orgasmic sensation can occur. The key distinction is between ejaculation (the physical release of seminal fluid) and fertility (the presence of viable sperm within that fluid)—the seminal fluid typically contains significantly fewer or no sperm cells during treatment.

For men wishing to preserve fertility, the primary approach should be to avoid TRT if actively trying to conceive. Sperm banking before initiating treatment provides a definitive fertility preservation option. In some specialist settings, alternative treatments such as human chorionic gonadotropin (hCG) with or without FSH, or clomifene (off-label), may be considered instead of conventional testosterone therapy.

The MHRA-approved product information for testosterone preparations clearly states that men of reproductive age should receive comprehensive counselling about these fertility implications before commencing testosterone therapy, ensuring informed decision-making about their reproductive future.

Managing Sexual Side Effects During Treatment

Whilst testosterone replacement therapy is often prescribed to improve sexual symptoms associated with hypogonadism—including low libido and erectile dysfunction—some men experience unexpected sexual side effects during treatment. Understanding these potential effects and management strategies is essential for optimising treatment outcomes.

Common sexual side effects may include changes in erectile function, alterations in libido (either increased or, paradoxically, decreased in some cases), and changes in orgasmic sensation. Some men report differences in ejaculatory experience, though these effects vary considerably between individuals. Testicular atrophy (shrinkage) occurs in many men due to reduced LH stimulation, which, whilst not directly affecting sexual function, can cause psychological distress.

Other common side effects include acne or oily skin, fluid retention, application site reactions with gels, and increased red blood cell production (erythrocytosis). Men using testosterone gel must take precautions to avoid transferring the medication to partners or children through skin contact.

Management approaches should be individualised and may include:

• Dose optimisation: Working with your clinician to adjust testosterone dosage or change delivery method can help minimise side effects whilst maintaining therapeutic benefits

• Monitoring and adjustment: Regular blood tests ensure testosterone levels remain within target range—levels that are too high or too low can both cause sexual dysfunction

• Addressing concurrent factors: Cardiovascular health, diabetes control, psychological wellbeing, and relationship factors all significantly influence sexual function and should be addressed holistically

• Combination therapies: For persistent erectile dysfunction, phosphodiesterase-5 inhibitors (such as sildenafil) can be used alongside TRT in most men, but must never be used with nitrate medications

It's worth noting that sexual function improvements from TRT typically develop gradually over 3–6 months. Men should maintain realistic expectations and understand that testosterone therapy addresses only the hormonal component of sexual function. If you experience any suspected side effects from testosterone treatment, you can report these through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

When to Speak with Your GP About Concerns

Open communication with your GP or specialist is essential throughout testosterone treatment. Certain symptoms or concerns warrant prompt medical review to ensure treatment safety and effectiveness, and to address any complications early.

You should contact your GP if you experience:

• Significant changes in sexual function that concern you or affect your quality of life, including new or worsening erectile dysfunction, complete loss of libido, or painful ejaculation

• Fertility concerns: If you're planning to conceive or have concerns about future fertility, discuss this before starting treatment or as soon as the concern arises

• Testicular pain or significant shrinkage that causes discomfort or distress

• Mood changes, including depression, anxiety, irritability, or aggression

• Physical symptoms such as breast tenderness or enlargement (gynaecomastia), unexplained weight gain, persistent headaches, or visual disturbances

• Cardiovascular symptoms including chest pain, shortness of breath, or leg swelling, as testosterone can affect red blood cell production and cardiovascular risk

Seek urgent medical attention (call 999 or 111) for acute chest pain, severe shortness of breath, unilateral leg swelling, or urinary retention.

Regular monitoring is a fundamental component of safe testosterone therapy. Blood tests are typically performed at 3, 6, and 12 months after initiation, then at least annually thereafter. These tests assess testosterone levels, full blood count (to monitor for high haematocrit, which should remain below 0.54), liver function, and in men over 50 or at increased risk, prostate-specific antigen (PSA) with digital rectal examination according to local policy.

Before starting treatment, ensure you've had a thorough discussion about your reproductive plans, as decisions about fertility preservation must be made proactively. If you're currently on treatment and circumstances change—such as deciding you'd like to father children—speak with your GP promptly about options including treatment modification or temporary cessation of TRT.

Your healthcare provider can also refer you to specialist services when appropriate, including urology for complex sexual dysfunction, endocrinology or andrology clinics for comprehensive male reproductive health assessment, or NHS fertility services for fertility concerns. Never discontinue testosterone therapy abruptly without medical guidance, as this can cause significant hormonal fluctuations and symptom recurrence.

Frequently Asked Questions