Does tadalafil increase muscle growth? This question has emerged in fitness communities, but the evidence does not support tadalafil as a muscle-building agent. Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor licensed in the UK for erectile dysfunction, benign prostatic hyperplasia, and pulmonary arterial hypertension. Whilst it improves blood flow by relaxing vascular smooth muscle, there is no robust clinical evidence demonstrating meaningful effects on skeletal muscle mass or strength in healthy individuals. Using tadalafil off-licence for bodybuilding purposes carries health risks without proven benefits. This article examines the evidence, potential risks, and safe, evidence-based approaches to muscle development.

What Is Tadalafil and How Does It Work in the Body?

Tadalafil is a prescription medication primarily licensed in the UK for the treatment of erectile dysfunction (ED), benign prostatic hyperplasia (BPH), and pulmonary arterial hypertension (PAH). It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, which also includes sildenafil and vardenafil. The Medicines and Healthcare products Regulatory Agency (MHRA) has approved tadalafil under brand names such as Cialis, as well as generic formulations.

The drug works by inhibiting the PDE5 enzyme, which is responsible for breaking down cyclic guanosine monophosphate (cGMP) in smooth muscle cells. When PDE5 is blocked, cGMP levels increase, leading to relaxation of smooth muscle in blood vessel walls. This results in vasodilation—widening of blood vessels—which improves blood flow to specific areas of the body, particularly the penis during sexual stimulation. In BPH, tadalafil works by relaxing smooth muscle in the prostate and bladder neck, helping to relieve urinary symptoms.

Tadalafil is available in different strengths (2.5 mg, 5 mg, 10 mg, and 20 mg) and can be taken either on-demand (typically 10-20 mg for ED) or as a daily low-dose regimen (2.5-5 mg for ED; 5 mg for BPH), depending on the indication. The medication has a relatively long half-life of approximately 17.5 hours, which distinguishes it from other PDE5 inhibitors and allows for more flexible dosing. After oral administration, tadalafil is absorbed from the gastrointestinal tract and metabolised primarily in the liver by the cytochrome P450 enzyme CYP3A4.

It is important to note that tadalafil is not licensed or indicated for muscle building, athletic performance enhancement, or bodybuilding purposes. Its mechanism of action targets vascular smooth muscle rather than skeletal muscle tissue, and there is no official therapeutic indication for its use in muscle growth or strength training.

Does Tadalafil Increase Muscle Growth? Examining the Evidence

The question of whether tadalafil increases muscle growth has gained attention in fitness communities, but the scientific evidence does not support its use as a muscle-building agent. While some animal studies have suggested potential effects on muscle metabolism, these findings have not been replicated in robust human clinical trials, and there is no official link established between tadalafil use and increased muscle mass in humans.

Some preliminary research has explored whether PDE5 inhibitors might influence muscle blood flow during exercise. The theoretical rationale is that improved blood flow could enhance nutrient and oxygen delivery to working muscles, potentially supporting performance or recovery. However, the available evidence in healthy individuals shows inconsistent or negligible effects on exercise capacity, muscle strength, or hypertrophy. The vasodilatory effects of tadalafil appear to be predominantly localised to specific vascular beds and current evidence does not demonstrate meaningful changes in skeletal muscle physiology in healthy individuals.

A small number of studies have investigated PDE5 inhibitors in clinical populations with muscle-wasting conditions, such as Duchenne muscular dystrophy or heart failure-related cachexia. Results have been mixed, with most trials in Duchenne muscular dystrophy showing negative outcomes. Any modest improvements in exercise tolerance seen in heart failure patients relate to disease-specific cardiovascular mechanisms rather than direct effects on muscle growth in healthy individuals.

The absence of high-quality evidence means that any claims about tadalafil promoting muscle growth remain speculative and unsupported by regulatory bodies such as NICE or the MHRA. No UK regulator endorses tadalafil for muscle growth, and use for bodybuilding purposes is off-licence and not recommended. Healthcare professionals should be aware that patients may encounter such claims online or in fitness forums, but these are not grounded in evidence-based medicine. Using tadalafil off-licence for bodybuilding purposes carries risks without proven benefits.

Potential Risks of Using Tadalafil for Muscle Building

Using tadalafil for unapproved purposes such as muscle building exposes individuals to unnecessary health risks without established benefits. As with all medications, tadalafil can cause adverse effects, and taking it without medical supervision or appropriate indication increases the likelihood of harm.

Common adverse effects of tadalafil include:

• Headache (very common)

• Dyspepsia (indigestion) and gastrointestinal discomfort (common)

• Back pain and myalgia (muscle aches), which typically resolve within 48 hours (common)

• Flushing and nasal congestion (common)

• Dizziness, particularly when standing quickly due to blood pressure changes (common)

More serious risks include cardiovascular effects. Tadalafil can cause hypotension (low blood pressure), especially when combined with nitrates, which is contraindicated and potentially life-threatening. Nitrates should not be used for at least 48 hours after taking tadalafil due to its long half-life. The combination with guanylate cyclase stimulators (such as riociguat) is also contraindicated. Use with alpha-blockers requires caution due to the risk of hypotension, and the combination for treating LUTS/BPH is generally not recommended.

Individuals with underlying cardiovascular disease, including recent myocardial infarction, unstable angina, or uncontrolled hypertension, should not use tadalafil without specialist assessment. Seek immediate medical attention if chest pain occurs during or after sexual activity.

There is also a risk of priapism—a prolonged, painful erection lasting more than four hours—which constitutes a medical emergency requiring immediate treatment to prevent permanent tissue damage. Visual disturbances, including rare cases of non-arteritic anterior ischaemic optic neuropathy (NAION), and sudden hearing loss have been reported with PDE5 inhibitors and require urgent medical attention.

Drug interactions represent another significant concern. Tadalafil is metabolised by CYP3A4 enzymes, and concurrent use of strong inhibitors (such as ritonavir, ketoconazole, or clarithromycin) can substantially increase tadalafil plasma concentrations, raising the risk of adverse effects. Conversely, CYP3A4 inducers may reduce efficacy.

Obtaining tadalafil without prescription—through online sources or the black market—carries additional risks, including counterfeit or contaminated products that may contain incorrect doses or harmful substances. Always use GPhC-registered pharmacies and avoid unregulated sources. Suspected side effects should be reported via the MHRA Yellow Card scheme. Individuals considering or currently using tadalafil for non-approved purposes should consult their GP to discuss safer, evidence-based alternatives.

Safe and Evidence-Based Approaches to Building Muscle Mass

For individuals seeking to increase muscle mass, there are well-established, evidence-based strategies that are both safe and effective, without resorting to off-licence medication use. The UK Chief Medical Officers' Physical Activity Guidelines and NHS advice emphasise the importance of structured exercise and adequate nutrition as the cornerstones of muscle development.

Progressive resistance training is the most effective method for stimulating muscle hypertrophy. This involves:

• Compound exercises such as squats, deadlifts, bench presses, and rows that engage multiple muscle groups

• Progressive overload—gradually increasing weight, repetitions, or training volume over time

• Adequate frequency—training each major muscle group 2–3 times per week

• Proper form and technique to maximise effectiveness and minimise injury risk

Nutritional support is equally critical. For individuals undertaking regular resistance training, protein intake should be optimised, with evidence suggesting 1.6–2.2 grams per kilogram of body weight daily. Those with kidney disease or other health conditions should consult a healthcare professional before increasing protein intake. Protein should be distributed across meals to support muscle protein synthesis. Whole food sources such as lean meats, fish, eggs, dairy, legumes, and plant-based proteins are preferable to supplements, though whey or plant-based protein powders can be convenient adjuncts.

Adequate energy intake is essential—muscle growth requires a caloric surplus or at minimum, sufficient calories to support training demands. Carbohydrates provide fuel for intense workouts, while healthy fats support hormone production, including testosterone, which plays a role in muscle development.

Recovery and sleep are often underestimated but crucial components. Muscle repair and growth occur during rest periods, and inadequate sleep (aim for 7–9 hours nightly) can impair recovery and hormonal balance, including growth hormone and testosterone secretion.

For individuals with specific health conditions, underlying hormonal imbalances, or those not responding to standard approaches, consultation with a GP or sports medicine specialist is appropriate. Conditions such as hypogonadism (low testosterone) can be properly diagnosed and treated under medical supervision. Referral to a registered dietitian or exercise physiologist may also be beneficial for personalised guidance. These evidence-based approaches offer sustainable, safe results without the risks associated with off-licence medication use.

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