Tadalafil Tablets UK: Uses, Dosage and How to Buy Safely
Tadalafil tablets are long-acting PDE5 inhibitors used mainly to treat erectile dysfunction in adult men. In the UK they are supplied in authorised 2.5mg, 5mg, 10mg and 20mg strengths, with dosing based on whether tadalafil is used on demand or once daily.
Tadalafil is also used at specific doses for urinary symptoms associated with benign prostatic hyperplasia, and specialist products are used for pulmonary arterial hypertension.
The key questions are not just which strength to choose, but whether the medicine is suitable, how daily and on-demand regimens differ, what interactions matter, and how to avoid illegal or counterfeit supply.
Key things to know
- For on-demand treatment, the usual starting dose is 10mg, taken at least 30 minutes beforehand
- 20mg may be considered where 10mg does not provide an adequate effect
- The maximum standard frequency is once per day
- For frequent use, the daily regimen is 5mg once a day, reducible to 2.5mg for tolerability
- Tadalafil can remain effective for up to around 36 hours after an on-demand dose
- It can be taken with or without food, and still requires sexual stimulation to work
What Tadalafil Tablets Are
Tadalafil belongs to a group of medicines called phosphodiesterase type 5 inhibitors.
During appropriate stimulation, nitric oxide increases the concentration of a chemical messenger called cGMP, which helps smooth muscle relax so blood can flow more easily into erectile tissue.
PDE5 normally breaks cGMP down. Tadalafil inhibits it, allowing that signalling pathway to remain active for longer.
It supports the natural blood-flow response, but only assists in producing an erection when stimulation occurs.
What They Are Used For
The main use is erectile dysfunction in adult men. Depending on the strength and product licence, tadalafil is also used for:
- Benign prostatic hyperplasia
- Erectile dysfunction and benign prostatic hyperplasia occurring together
- Pulmonary arterial hypertension, under specialist treatment
The dose used for one condition should not be applied to another. Tadalafil 20mg on demand is a very different thing from tadalafil 5mg once daily.
UK Strengths and What Each Is For
Authorised UK products include 2.5mg, 5mg, 10mg and 20mg tablets, each with a different practical role.
| Strength | Role |
|---|---|
| 2.5mg | Reduced once-daily dose where 5mg daily is not well tolerated. Not an on-demand dose |
| 5mg | The usual once-daily dose for frequent treatment, and the standard dose for benign prostatic hyperplasia, including in men treated for both conditions |
| 10mg | The usual starting dose for on-demand treatment |
| 20mg | The maximum standard on-demand dose, considered where 10mg has not produced an adequate response |
The Normal Dose
For on-demand treatment: 10mg to start, increasing to 20mg if required and appropriate. Maximum once per day, and no more than one tablet in any 24 hours.
For daily treatment: 5mg once daily, potentially reduced to 2.5mg according to tolerability.
For benign prostatic hyperplasia: 5mg once daily.
These regimens should not be mixed independently. Tadalafil supports erections around sexual activity but does not increase desire.
Are 10mg and 20mg Daily Tablets?
No. UK prescribing information states that 10mg and 20mg are intended for use before anticipated sexual activity, and are not recommended for continuous daily use.
If frequent treatment is required, the lower once-daily regimen is the appropriate route, at 5mg or in some cases 2.5mg.
How the Two Regimens Work
On Demand
On-demand tadalafil is taken before it is expected to be needed, at least 30 minutes beforehand.
Its long duration means the timing does not need planning as precisely as with some shorter-acting options.
Daily
Daily tadalafil maintains relatively consistent exposure rather than linking each tablet to a particular occasion. The usual dose is 5mg once daily at approximately the same time each day.
That suits people who anticipate needing treatment frequently. It does not mean an erection is continuously present. Stimulation is still required.
How Long It Takes to Work
For on-demand treatment, tadalafil can begin supporting an erectile response from approximately 30 minutes after dosing. The effect is not necessarily at its maximum at exactly 30 minutes.
Individual response depends on the dose, metabolism, the underlying cause, stimulation and other medicines.
How Long It Lasts
Tadalafil may remain capable of supporting an erectile response for up to approximately 36 hours after an on-demand dose. The NHS also notes that effects can last up to 36 hours.
That does not mean an erection lasts 36 hours. It means tadalafil may continue to assist the normal response within that period when stimulation occurs.
Food
Tadalafil can be taken with or without food, which is a practical difference from some other PDE5 inhibitors whose absorption can be delayed by high-fat meals.
You do not need to avoid meals or take it on an empty stomach.
How It Compares With Sildenafil
Viagra contains sildenafil, not tadalafil. They are different medicines within the same PDE5 inhibitor class, so a tablet labelled tadalafil should not be described as Viagra.
Both work the same way, but their duration differs substantially. Tadalafil is known for a treatment window of up to 36 hours, while sildenafil is shorter acting and generally taken closer to anticipated activity.
Tadalafil also has a recognised 5mg once-daily regimen, while sildenafil is generally used on demand.
Which suits you better depends on medical suitability, how often you need treatment, side effects and preference.
Generic Tadalafil
Authorised generic tadalafil contains the same active ingredient at the labelled dose, and is expected to be equivalent even where the presentation differs. UK listings show numerous authorised products from multiple manufacturers.
Generic tablets can differ in shape, colour, markings, packaging and inactive ingredients, but the active medicine remains tadalafil.
Appearance depends on the manufacturer, so it is not a reliable way to judge whether a tablet is genuine. More useful checks are regulated supply, original packaging, the patient information leaflet, the manufacturer, the labelled dose and the pharmacy's details.
Buying Tadalafil in the UK
Tadalafil is available through pharmacy and prescription routes. The NHS states that it is mostly available with a prescription, although a specific 10mg pharmacy product can be supplied after an appropriate pharmacist assessment.
The MHRA's reclassification applies to that particular 10mg product for adult men. Other tadalafil medicines remain available through prescription routes.
That does not mean every tadalafil tablet can be bought without clinical checks. For most products a prescribing assessment is required, and even the pharmacy route involves a professional suitability assessment.
Buying Online
Buying online is safe only through regulated pharmacy and prescribing routes. For prescription tadalafil, the process typically involves:
- Completing a confidential medical questionnaire
- Clinical review by an independent prescriber
- Confirmation of suitability
- A prescription being issued
- Pharmacy dispensing
- Delivery
Tadalafil has significant contraindications and interactions, including with nitrates and riociguat, which is exactly what that process exists to catch.
A service offering tadalafil with no questions asked should not be regarded as offering a benefit.
Checking a Seller
The MHRA advises avoiding erectile dysfunction medicines sold through unknown websites, social media accounts or messaging apps, because unauthorised medicines may contain the wrong amount of active ingredient, no active ingredient at all, or harmful substances.
You can also use the MHRA's online service to check whether a website appears on its Not Recommended list.
Warning signs include no medical assessment, no pharmacist involvement, no verifiable pharmacy information, social media or messaging-app ordering, claims of unrestricted prescription medicine supply, and unusual or unlicensed strengths.
The Scale of Illegal Supply
The MHRA reported that approximately 19.5 million illegally traded erectile dysfunction medicine doses were seized between 2021 and 2025, including products containing tadalafil. About 4.4 million were seized in 2025 alone.
The MHRA has also warned that unauthorised products may contain no active ingredient, excessive active ingredient, or toxic substances.
That creates particular risks because tadalafil interacts seriously with cardiovascular medicines. A tablet containing more tadalafil than stated can increase adverse effects, while one containing none may lead someone to take extra doses unnecessarily.
Safety and Interactions
An assessment should consider cardiovascular disease, blood pressure, nitrate medicines, riociguat, kidney and liver function, alpha blockers, other erectile dysfunction medicines and any medicines affecting CYP3A4.
Prescribing information contains important cardiovascular contraindications, including certain recent heart attacks, recent strokes, unstable angina, uncontrolled arrhythmias and very low blood pressure.
Nitrates and Riociguat
Tadalafil must not be taken with organic nitrate medicines, because the combination can cause potentially dangerous blood pressure lowering.
That applies at every strength, and to both daily and on-demand use. Changing the dose does not remove the interaction.
It should not be combined with riociguat either, for the same reason.
Blood Pressure Medicines and Alpha Blockers
Because tadalafil can lower blood pressure, it may add to the effects of antihypertensive medicines. Some combinations are relatively well tolerated, while others require more caution, so give a complete current medicine list during the consultation.
Alpha blockers also lower blood pressure. Pharmacy guidance states that people taking them should discuss treatment with a prescriber, since a lower daily dose may sometimes be more appropriate.
Antibiotics and Grapefruit
Tadalafil is primarily metabolised through CYP3A4, and medicines that inhibit that enzyme can increase exposure. Examples include erythromycin, clarithromycin, ketoconazole and itraconazole.
Grapefruit juice can inhibit CYP3A4 in the same way. Pharmacy guidance advises people using CYP3A4 inhibitors, including grapefruit juice, to seek medical advice, because a different regimen may be more suitable.
Alcohol
Small amounts may be tolerated by many people, but excessive alcohol can increase dizziness, light-headedness on standing and low blood pressure.
It can also independently make erectile function less reliable. Authorised pharmacy guidance advises avoiding large amounts before anticipated activity.
Other ED Medicines
Do not independently combine tadalafil with sildenafil, vardenafil or avanafil. Tadalafil information states that the safety and effectiveness of such combinations have not been established.
A poor response to one tablet should prompt a treatment review rather than unsupervised stacking.
Side Effects
Recognised side effects include headache, dizziness, indigestion, back pain, muscle pain, limb pain, facial flushing and nasal congestion.
Most are mild to moderate and temporary, and the exact likelihood depends partly on dose and individual susceptibility.
Headache is among the most commonly reported, and may be more noticeable during the early stages of treatment. Back pain and muscle aches are particularly recognised with tadalafil compared with some shorter-acting PDE5 inhibitors. Less common gastrointestinal effects include reflux, stomach discomfort, nausea and vomiting.
Persistent or severe symptoms should be discussed with a pharmacist or prescriber.
When to Seek Urgent Help
An erection lasting four hours or longer is a medical emergency, because prolonged pressure can damage erectile tissue. It is not a sign that the medicine is working especially well.
A sudden decrease or loss of vision requires urgent assessment. Do not wait for a significant visual change to resolve on its own.
Sudden hearing decrease or loss has also been reported with PDE5 inhibitors. Seek prompt attention for sudden hearing changes, particularly alongside tinnitus or dizziness.
If It Does Not Work
Several factors can contribute to apparent treatment failure: insufficient time, inadequate stimulation, the wrong dose, heavy alcohol use, interactions, severe underlying erectile dysfunction, or unrealistic expectations.
If 10mg has been used correctly but remains insufficient, 20mg may be considered after clinical assessment. Do not increase the dose beyond 20mg for ordinary treatment.
Do not take tadalafil more often than prescribed. The maximum frequency is once per day. If treatment repeatedly fails, check dose, timing, stimulation, other medicines and underlying causes rather than taking extra tablets.
The Key Takeaway
Tadalafil tablets are long-acting PDE5 inhibitors available in several UK strengths, with different doses designed for different treatment patterns.
For on-demand treatment, the normal starting dose is 10mg, with 20mg considered when 10mg is insufficient, taken at least 30 minutes beforehand and no more than once per day.
For daily treatment, the normal regimen is 5mg once daily, with possible reduction to 2.5mg. 5mg once daily is also the established dose for benign prostatic hyperplasia, and 20mg should not be used as a stronger daily alternative.
Tadalafil has a long duration, remaining capable of supporting an erectile response for up to approximately 36 hours after an on-demand dose, and can be taken with or without food.
Most products are supplied through prescription routes, although a specific authorised 10mg pharmacy medicine can be supplied following pharmacist assessment. Either way, the medicine should come through a legitimate UK pharmacy and a proper clinical assessment.
