Erectile dysfunction affects a significant number of men across the UK — estimates suggest around half of all men between 40 and 70 experience some degree of difficulty achieving or maintaining erections. Despite being so common, it remains a topic many men find difficult to discuss, which means too many go without effective treatment that could genuinely improve their quality of life.
Tadalafil is one of the most widely prescribed medications for erectile dysfunction in the UK. You may know it better by its original brand name, Cialis. Since the patent expired in 2017, generic tadalafil has become significantly more affordable and accessible, making it a practical option for men who previously found the cost prohibitive.
This guide covers everything you need to know about using tadalafil for erectile dysfunction: how it works, the different dosing options, who can and cannot take it, what side effects to expect, how it compares to sildenafil (Viagra), and importantly, when erectile dysfunction might be signalling something else that deserves clinical attention.
What Is Tadalafil?
Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor. It was first approved for the treatment of erectile dysfunction in 2003 under the brand name Cialis and quickly became one of the most prescribed ED medications worldwide. It is also licensed for the treatment of benign prostatic hyperplasia (BPH) and pulmonary arterial hypertension (under the brand name Adcirca), though this guide focuses on its use for erectile dysfunction.
PDE5 inhibitors are a class of medications that also includes sildenafil (Viagra), vardenafil (Levitra), and avanafil (Spedra). What distinguishes tadalafil from its counterparts is its remarkably long duration of action — up to 36 hours, which earned it the nickname “the weekend pill.”
How Tadalafil Works
To understand how tadalafil works, it helps to understand the physiology of an erection. When a man becomes sexually aroused, the brain sends signals through the nervous system that trigger the release of nitric oxide in the erectile tissue of the penis. Nitric oxide activates an enzyme called guanylate cyclase, which increases levels of a chemical messenger called cyclic guanosine monophosphate (cGMP). It is cGMP that causes the smooth muscle in the blood vessels of the penis to relax, allowing blood to flow in and produce an erection.
The enzyme PDE5 breaks down cGMP. In men with erectile dysfunction, this breakdown happens too quickly or the cGMP response is insufficient, meaning the blood flow needed for a firm erection is not adequately maintained.
Tadalafil blocks the PDE5 enzyme, preventing it from breaking down cGMP. This allows cGMP to accumulate and do its job more effectively, promoting stronger and longer-lasting blood flow to the penis during sexual arousal.
Important: Tadalafil does not cause erections on its own. Sexual stimulation is still required to initiate the release of nitric oxide and start the process. The medication simply enhances the body’s natural response to arousal.
Dosage Options
One of the significant advantages of tadalafil is the flexibility in how it can be dosed. There are two distinct prescribing approaches, and the right one for you depends on how frequently you have sexual intercourse and your personal preferences.
On-demand dosing (10 mg or 20 mg)
This approach involves taking a tablet before anticipated sexual activity. The standard starting dose is 10 mg, taken at least 30 minutes before sex, though many men find the medication works best if taken one to two hours beforehand. If 10 mg is insufficient, your clinician may increase the dose to 20 mg. If 10 mg produces good results with notable side effects, the dose may be reduced to 5 mg.
The key advantage of on-demand dosing is the long window of effectiveness. Unlike sildenafil, which is typically effective for four to six hours, a single dose of tadalafil can remain active for up to 36 hours. This does not mean you will have an erection for 36 hours — it means that during that window, your ability to achieve and maintain an erection in response to sexual stimulation is enhanced. This longer window provides significantly more spontaneity and removes the pressure of precise timing.
On-demand dosing is best suited for: Men who have sexual intercourse once or twice per week and prefer to take medication only when needed.
Daily dosing (2.5 mg or 5 mg)
The daily dosing approach involves taking a low dose of tadalafil every day, at approximately the same time, regardless of whether sexual activity is planned. The standard daily dose is 5 mg, though 2.5 mg may be sufficient for some men.
Daily dosing maintains a constant low level of tadalafil in the bloodstream, which means the medication is always working. There is no need to plan around taking a tablet — you are always ready. This approach tends to produce the most natural-feeling sexual experience, as the medication effect is consistent rather than peaking and fading.
Daily dosing is best suited for: Men who have sexual intercourse more than twice per week, men who prefer complete spontaneity, men who also have symptoms of benign prostatic hyperplasia (daily tadalafil is licensed for this), and men who experience anxiety around the timing of on-demand medication.
| Dosing Approach | Dose | When to Take | Duration of Effect | Best For |
|---|---|---|---|---|
| On-demand | 10 mg or 20 mg | 30–60 minutes before sexual activity | Up to 36 hours | Less frequent intercourse; flexible timing |
| Daily | 2.5 mg or 5 mg | Same time each day | Continuous | Frequent intercourse; maximum spontaneity |
How Long Does Tadalafil Last?
The duration of action is where tadalafil truly distinguishes itself from other PDE5 inhibitors. After a single on-demand dose, the medication reaches peak plasma concentration in approximately two hours, but clinically significant effects can last for up to 36 hours. Some studies have shown residual effects extending beyond this window, though the effect diminishes over time.
This extended duration is due to tadalafil’s pharmacokinetic profile. It has a half-life of approximately 17.5 hours — substantially longer than sildenafil (approximately 4 hours) or vardenafil (approximately 5 hours). This means tadalafil is eliminated from the body much more slowly, providing a prolonged therapeutic window.
For the daily dosing regimen, steady-state blood levels are typically achieved within five days of starting treatment, after which the effect is continuous.
Side Effects of Tadalafil
Like all medications, tadalafil can cause side effects. Most are mild to moderate, dose-dependent, and tend to diminish with continued use as the body adjusts. The most common side effects reported in clinical trials include:
Common side effects (affecting more than 1 in 10 users)
- Headache: The most frequently reported side effect. Usually mild and responds to standard over-the-counter pain relief. Tends to become less frequent with continued use.
- Dyspepsia (indigestion): A sensation of discomfort or burning in the upper abdomen. Taking the medication with food can help reduce this.
Common side effects (affecting 1 in 10 to 1 in 100 users)
- Flushing: Warmth and redness in the face and neck due to blood vessel dilation.
- Nasal congestion: A blocked or stuffy nose caused by vasodilation in the nasal passages.
- Back pain and myalgia (muscle pain): More commonly reported with tadalafil than with other PDE5 inhibitors. Usually occurs 12 to 24 hours after taking the medication and resolves within 48 hours. This side effect is thought to relate to PDE5 inhibition in smooth muscle outside the penis.
Uncommon side effects
- Dizziness
- Blurred vision
- Tinnitus (ringing in the ears)
- Palpitations
- Skin rash
Rare but serious side effects
- Priapism: A prolonged, painful erection lasting more than four hours. This is a medical emergency requiring immediate treatment. It is extremely rare with PDE5 inhibitors but men should be aware of it.
- Sudden hearing loss: Very rarely reported. Seek medical attention immediately if you experience sudden reduction or loss of hearing.
- Non-arteritic anterior ischaemic optic neuropathy (NAION): A very rare condition affecting blood supply to the optic nerve, which can cause sudden vision loss. Men with certain pre-existing eye conditions may be at higher risk.
If you experience any concerning side effects, contact your prescribing clinician or seek medical attention as appropriate.
Who Can and Cannot Take Tadalafil
Tadalafil is suitable for most men with erectile dysfunction, but there are important contraindications and precautions that must be assessed before prescribing.
Absolute contraindications (you must not take tadalafil if):
- You take nitrate medications: This includes glyceryl trinitrate (GTN spray or patches), isosorbide mononitrate, isosorbide dinitrate, and recreational nitrates (“poppers” containing amyl nitrite or butyl nitrite). The combination of tadalafil with nitrates can cause a severe and potentially life-threatening drop in blood pressure. This is the single most important safety consideration with all PDE5 inhibitors.
- You have had a recent heart attack or stroke: Generally, PDE5 inhibitors should be avoided for at least 90 days after a major cardiovascular event.
- You have severe liver or kidney impairment: Dose adjustments are required for moderate impairment; tadalafil may not be appropriate for severe impairment.
- You have a known allergy to tadalafil or any of its excipients.
Use with caution:
- Men taking alpha-blocker medications for prostate conditions (risk of hypotension)
- Men with certain cardiovascular conditions where sexual activity itself carries risk
- Men with anatomical penile deformities (e.g., Peyronie’s disease)
- Men with conditions predisposing to priapism (e.g., sickle cell anaemia, multiple myeloma, leukaemia)
A thorough medical assessment is essential before starting tadalafil. This is why it is a prescription-only medication in the UK — a clinician needs to review your medical history, current medications, and cardiovascular status to ensure it is safe for you.
Tadalafil vs Sildenafil (Viagra): How Do They Compare?
This is one of the most common questions men ask when exploring ED treatment. Both are PDE5 inhibitors with proven efficacy, but there are meaningful differences that may make one more suitable than the other depending on your circumstances.
| Feature | Tadalafil (Cialis) | Sildenafil (Viagra) |
|---|---|---|
| Duration of action | Up to 36 hours | 4–6 hours |
| Onset of action | 30–60 minutes | 30–60 minutes |
| Effect of food | Minimal impact | Reduced absorption with fatty meals |
| Daily dosing option | Yes (2.5 mg or 5 mg) | No (on-demand only) |
| Back pain as side effect | More common | Less common |
| Visual disturbances | Less common | More common (blue tinge to vision) |
| Available OTC in UK | No (prescription only) | Yes (Viagra Connect 50 mg, pharmacy only) |
| Generic cost (approx.) | £0.50–£2 per tablet | £0.30–£1.50 per tablet |
The most clinically significant difference is duration of action. Tadalafil’s 36-hour window provides far more flexibility and spontaneity than sildenafil’s four-to-six-hour window. Many men and their partners prefer this because it removes the need to time sexual activity around when the medication was taken.
Tadalafil is also less affected by food. A fatty meal can significantly delay the absorption of sildenafil, reducing its effectiveness. Tadalafil can be taken with or without food with minimal impact on its performance.
On the other hand, sildenafil is available over the counter in the UK as Viagra Connect (50 mg), which can be purchased from pharmacies without a prescription after a pharmacist consultation. Tadalafil remains prescription-only, though obtaining a prescription from an online or private clinic is straightforward.
Neither medication is objectively “better” — the right choice depends on your lifestyle, frequency of sexual activity, side effect profile, and personal preference. Some men try both and settle on the one that works best for them.
Cost of Tadalafil in the UK
When tadalafil was only available as branded Cialis, it was expensive — often £30 or more for four tablets. Since the patent expired in 2017, generic tadalafil has become dramatically more affordable.
Current generic tadalafil prices in the UK typically range from:
- On-demand (10 mg or 20 mg): Approximately £0.50 to £2 per tablet through legitimate online pharmacies and clinics.
- Daily (5 mg): Approximately £0.30 to £1 per tablet, which works out to roughly £9 to £30 per month.
Tadalafil is also available on the NHS for erectile dysfunction. Since April 2023, NHS England guidelines have allowed GPs to prescribe generic tadalafil for ED without the quantity restrictions that previously applied. This means that for men registered with an NHS GP, tadalafil may be available for the standard prescription charge (£9.90 per item in England, or free in Scotland, Wales, and Northern Ireland).
If you are purchasing tadalafil privately, ensure you are using a legitimate, regulated provider. The MHRA maintains a register of approved online pharmacies. Avoid purchasing from unregulated sources, as counterfeit ED medications are one of the most commonly encountered fake drugs in the UK.
When to See a Doctor About Erectile Dysfunction
While tadalafil is an effective treatment for the symptom of erectile dysfunction, it is important to recognise that ED can be a marker of underlying health conditions that deserve investigation in their own right.
Erectile dysfunction shares many risk factors with cardiovascular disease: it is associated with diabetes, hypertension, high cholesterol, obesity, and smoking. In some cases, ED can be an early warning sign of cardiovascular disease, appearing several years before more overt cardiac symptoms. The NHS recommends that men with ED have a cardiovascular risk assessment, particularly if they are over 40 or have other risk factors.
You should see a doctor about erectile dysfunction if:
- The problem is persistent (lasting more than a few weeks)
- It is causing distress or affecting your relationship
- You have other symptoms such as fatigue, low mood, reduced libido, or loss of morning erections (which may suggest hormonal causes)
- You have cardiovascular risk factors or a family history of heart disease
- You are taking medications that may contribute to ED (antidepressants, beta-blockers, etc.)
The Link Between Erectile Dysfunction and Low Testosterone
While PDE5 inhibitors like tadalafil address the vascular mechanism of erections, they do not address the hormonal component. Testosterone plays a crucial role in sexual desire, arousal, and erectile function. Men with low testosterone often experience reduced libido alongside erectile difficulties, and in these cases, tadalafil alone may not provide complete symptom resolution.
Research has shown that testosterone and PDE5 inhibitors work synergistically. Testosterone is needed for the production of nitric oxide synthase — the enzyme that produces the nitric oxide required to initiate the erection cascade. When testosterone levels are low, this pathway is impaired, which can reduce the effectiveness of PDE5 inhibitors.
If you have erectile dysfunction that responds poorly to PDE5 inhibitors, or if your ED is accompanied by other symptoms of low testosterone (fatigue, low mood, reduced muscle mass, increased body fat, poor concentration), we recommend having your testosterone levels checked. A comprehensive testosterone blood test can determine whether hormonal factors are contributing to your symptoms.
In men with confirmed low testosterone, testosterone replacement therapy combined with tadalafil often produces significantly better results than either treatment alone. Our clinicians at Evernu can assess whether this combined approach is appropriate for you.
Practical Tips for Getting the Best Results from Tadalafil
- Give it time: Tadalafil may not work perfectly the first time. The BSSM recommends trying a PDE5 inhibitor on at least six to eight occasions before concluding it is not effective for you.
- Timing matters (for on-demand): While tadalafil can work within 30 minutes, many men find it most effective when taken one to two hours before sexual activity.
- Reduce alcohol intake: Excessive alcohol impairs erectile function independently and can reduce the effectiveness of tadalafil.
- Address lifestyle factors: Regular exercise, a healthy diet, maintaining a healthy weight, good sleep, and stress management all support erectile function and can enhance the effects of medication.
- Communicate with your partner: Many men find that ED-related anxiety is itself a significant contributor to the problem. Open communication can reduce performance pressure.
- Do not buy from unregulated sources: Ensure your tadalafil comes from a registered pharmacy. Counterfeit medications may contain incorrect doses, no active ingredient at all, or dangerous contaminants.
Taking the Next Step
Erectile dysfunction is treatable, and there is no reason to accept it as an inevitable part of ageing. Whether tadalafil, lifestyle changes, testosterone optimisation, or a combination approach is right for you depends on your individual circumstances — and that starts with a proper clinical assessment.
If you are experiencing erectile difficulties alongside other symptoms such as fatigue, low mood, or reduced motivation, these may be signs of low testosterone. Our free online testosterone assessment can help you understand whether your symptoms warrant further investigation. If your concerns are primarily related to erectile function, speak with your GP or contact our clinical team to discuss treatment options.
You do not need to manage this alone, and effective help is available.
This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before starting or changing any medication. Evernu is regulated by the Regulation and Quality Improvement Authority (RQIA).
