Can Cialis cause gynaecomastia? This is an understandable concern for men prescribed tadalafil for erectile dysfunction or lower urinary tract symptoms in the UK. Gynaecomastia — the development of enlarged glandular breast tissue in men — has several well-established causes, including certain medicines and hormonal conditions. However, based on current clinical evidence and the MHRA-approved Summary of Product Characteristics, gynaecomastia is not a recognised adverse reaction of tadalafil. This article examines the pharmacology of Cialis, its known side effect profile, and what men should do if they notice breast changes during treatment.

Can Cialis Cause Gynaecomastia?

Gynaecomastia is not a recognised adverse reaction of tadalafil; neither the MHRA nor the EMA has identified breast tissue changes as an expected consequence of Cialis treatment.

Experiencing these side effects? Our pharmacists can help you navigate them →

Cialis (tadalafil) is a prescription medicine widely used in the UK to treat erectile dysfunction (ED) and lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH). One question that occasionally arises among patients and healthcare professionals is whether Cialis can cause gynaecomastia — the development of enlarged glandular breast tissue in men.

Based on current clinical evidence, the UK Summary of Product Characteristics (SmPC) approved by the European Medicines Agency (EMA) and referenced by the Medicines and Healthcare products Regulatory Agency (MHRA), gynaecomastia is not listed as a recognised adverse reaction of tadalafil. The EMA's European Public Assessment Report (EPAR) for Cialis similarly does not identify breast tissue changes as an expected consequence of treatment. There is no established pharmacological mechanism by which tadalafil directly causes breast tissue enlargement in men.

It is worth noting that breast swelling in men can sometimes reflect pseudogynaecomastia — fatty tissue enlargement due to obesity — rather than true glandular gynaecomastia. Clinical examination is needed to distinguish between the two, as their causes and management differ.

If a man taking Cialis notices breast swelling, tenderness, or nipple discharge, these symptoms should not be automatically attributed to tadalafil, nor should they be dismissed. They warrant prompt medical assessment to identify any underlying hormonal, hepatic, or medication-related cause. It is always advisable to speak to a GP or pharmacist rather than stopping prescribed medication without guidance.

How Tadalafil Works and Its Effects on Hormones

Tadalafil is a PDE5 inhibitor that does not interact with the hypothalamic-pituitary-gonadal axis and has no known direct effect on testosterone, oestrogen, prolactin, or aromatase activity.

Tadalafil belongs to a class of medicines known as phosphodiesterase type 5 (PDE5) inhibitors. Its primary mechanism of action involves blocking the PDE5 enzyme, which leads to increased levels of cyclic guanosine monophosphate (cGMP) in smooth muscle cells. This promotes relaxation of smooth muscle and vasodilation — particularly in the penile vasculature — facilitating erection. Tadalafil is also licensed to improve LUTS associated with BPH, although the precise mechanism underlying this benefit has not been fully established.

Importantly, tadalafil does not directly interact with the hypothalamic-pituitary-gonadal (HPG) axis, which governs testosterone and oestrogen production. It does not inhibit or stimulate aromatase — the enzyme responsible for converting androgens into oestrogens — and it has no known direct effect on prolactin levels. These hormonal pathways are the primary drivers of gynaecomastia development. Tadalafil does not meaningfully alter sex hormone concentrations, as reflected in the MHRA/EMC SmPC and EMA EPAR for Cialis.

However, men prescribed tadalafil for ED or LUTS may already have underlying conditions — such as hypogonadism, obesity, or liver disease — that independently predispose them to hormonal imbalances and gynaecomastia. Distinguishing between a drug effect and a pre-existing or concurrent condition is therefore essential in clinical assessment.

Known Side Effects of Cialis Reported in the UK

Common side effects of tadalafil include headache, flushing, dyspepsia, nasal congestion, back pain, and dizziness; gynaecomastia does not appear in the MHRA-approved SmPC.

The MHRA-approved SmPC for tadalafil outlines a well-characterised side effect profile. The most commonly reported adverse effects include:

• Headache — the most frequently reported side effect

• Flushing — due to peripheral vasodilation

• Dyspepsia and indigestion

• Nasal congestion

• Back pain and myalgia — dose-related; more common at higher doses (10–20 mg)

• Dizziness and hypotension — tadalafil is contraindicated with nitrate-based medicines (e.g., glyceryl trinitrate, isosorbide mononitrate) and with soluble guanylate cyclase (sGC) stimulators such as riociguat, due to the risk of severe hypotension; caution is required with alpha-blockers, and blood pressure should be monitored when tadalafil is used alongside other antihypertensive medicines

Less common but clinically important effects include:

• Visual disturbances, including non-arteritic anterior ischaemic optic neuropathy (NAION) — patients should seek immediate medical attention if sudden vision loss occurs

• Sudden hearing loss — requires immediate medical assessment

• Priapism — a prolonged erection lasting four hours or more is a medical emergency requiring urgent treatment to prevent permanent injury

Gynaecomastia does not appear in the SmPC as a listed adverse reaction for tadalafil, and neither the MHRA nor the EMA has issued any safety communication linking tadalafil to breast tissue changes.

Patients are encouraged to report any unusual or unexpected symptoms — including breast changes — through the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk or via the MHRA Yellow Card app. If breast changes occur during tadalafil treatment, a thorough medication review — including all concurrent medicines and supplements — is the appropriate first step.

Other Medicines and Conditions Linked to Gynaecomastia

Gynaecomastia is more commonly caused by medicines such as spironolactone, finasteride, or anti-androgens, and by conditions including hypogonadism, liver disease, and obesity, rather than tadalafil.

Gynaecomastia is a relatively common condition in men, affecting a significant proportion of adolescent boys transiently and a notable proportion of older men. It arises from an imbalance between oestrogen and androgen activity in breast tissue. Understanding its true cause requires a careful review of all potential contributing factors, including the distinction between true glandular gynaecomastia and pseudogynaecomastia (fatty enlargement without glandular proliferation).

Medicines commonly associated with gynaecomastia include:

• Spironolactone — an aldosterone antagonist with anti-androgenic properties

• 5-alpha-reductase inhibitors (e.g., finasteride, dutasteride) — used for BPH and male-pattern hair loss

• Anti-androgens (e.g., bicalutamide, cyproterone acetate) — used in prostate cancer treatment

• GnRH analogues (e.g., goserelin, leuprorelin) — used in prostate cancer

• Anabolic steroids and exogenous testosterone — through peripheral aromatisation to oestradiol

• Oestrogens — including those used in gender-affirming therapy

• Cimetidine — an older H2 receptor antagonist

• Digoxin — through oestrogen-like activity

• Ketoconazole and other azole antifungals — via inhibition of androgen synthesis

• Certain antiretrovirals (e.g., efavirenz) — mechanism not fully established

• Some antipsychotics and antidepressants — via hyperprolactinaemia

• Cannabis — an association has been reported, though the evidence remains mixed and inconclusive

Underlying medical conditions that can cause gynaecomastia include hypogonadism, hyperthyroidism, chronic liver disease, chronic kidney disease, and testicular, adrenal, or hCG-secreting tumours. Obesity is also a significant contributing factor, as adipose tissue contains aromatase, increasing peripheral oestrogen production.

For men taking Cialis who develop gynaecomastia, it is far more likely that the cause lies with one of the above factors rather than tadalafil itself. A thorough drug history, hormonal blood tests, and clinical examination are essential components of the diagnostic workup. Further information on causes and assessment is available via NICE Clinical Knowledge Summaries (CKS) on gynaecomastia and the NHS gynaecomastia page.

When to Speak to a GP or Pharmacist

Any man experiencing breast swelling, nipple tenderness, discharge, or a firm lump should seek prompt GP assessment; NICE NG12 recommends urgent two-week-wait referral for unexplained breast lumps in men aged 30 and over.

Any man who notices breast swelling, tenderness, or a lump beneath the nipple — whether or not he is taking Cialis or any other medication — should seek medical advice promptly. Whilst gynaecomastia is often benign, it can occasionally signal an underlying condition that requires investigation and treatment, and in rare cases may require assessment to exclude malignancy.

You should contact your GP if you experience:

• Unilateral or bilateral breast swelling or enlargement

• Nipple tenderness or pain

• Nipple discharge of any kind

• A firm or hard lump beneath the nipple

• Breast changes accompanied by other symptoms such as fatigue, weight changes, or reduced libido

Referral thresholds: In line with NICE guidance on suspected cancer recognition and referral (NG12), GPs should consider an urgent suspected cancer (two-week wait) referral for men aged 30 and over with an unexplained breast lump, or for those with suspicious skin changes or nipple abnormalities. Men aged 50 and over with unilateral nipple discharge, nipple retraction, or other concerning features should also be considered for urgent referral. If malignancy cannot be excluded clinically, urgent referral is appropriate regardless of age.

A pharmacist can also provide initial guidance, particularly regarding whether any other medicines — including over-the-counter products, herbal supplements, or bodybuilding supplements — may be contributing to hormonal changes. It is important not to stop taking prescribed medication without first consulting your GP, as abrupt discontinuation may carry its own risks.

Your GP may arrange blood tests to assess testosterone, luteinising hormone (LH), follicle-stimulating hormone (FSH), oestradiol, prolactin, human chorionic gonadotrophin (hCG), thyroid function, liver enzymes, and renal function. Testicular examination and, where indicated, testicular ultrasound should be considered to exclude an hCG-secreting tumour. Clinical examination will also help distinguish true glandular gynaecomastia from pseudogynaecomastia. In some cases, referral to an endocrinologist or urologist may be appropriate. Further guidance is available via NICE CKS on gynaecomastia and NICE NG12.

MHRA Guidance and Reporting Suspected Side Effects

The MHRA has not issued any safety communication linking tadalafil to gynaecomastia; suspected side effects should be reported via the Yellow Card scheme at yellowcard.mhra.gov.uk.

The MHRA is the UK's regulatory authority responsible for ensuring that medicines, including tadalafil, meet acceptable standards of safety, quality, and efficacy. The MHRA continuously monitors the safety of licensed medicines through post-marketing surveillance, including data collected via the Yellow Card scheme — the UK's system for reporting suspected adverse drug reactions (ADRs).

If you believe you have experienced a side effect from Cialis — including any unexpected symptom such as breast changes — you are encouraged to report it via the Yellow Card scheme at yellowcard.mhra.gov.uk or via the MHRA Yellow Card app. Reports can be submitted by patients, carers, and healthcare professionals alike. These reports contribute to the ongoing safety monitoring of medicines and can prompt regulatory review if a pattern of unexpected reactions emerges.

Healthcare professionals should also be aware that the EMA's pharmacovigilance framework requires manufacturers to submit periodic safety update reports (PSURs) for tadalafil, ensuring that any emerging signals — including rare or unexpected effects — are systematically evaluated. At present, neither the MHRA nor the EMA has issued any safety communication linking tadalafil to gynaecomastia.

In summary, current evidence does not support a causal link between Cialis and gynaecomastia. Any new or unexplained physical symptom during treatment should nonetheless be assessed clinically. Reporting suspected side effects through the Yellow Card scheme helps protect public health and supports the evidence base for medicine safety in the UK.

Frequently Asked Questions