Viagra (Sildenafil)

Viagra is available in three strengths for erectile dysfunction: 25mg, 50mg and 100mg. The most appropriate dose for you depends on your medical history, other medicines you take, how well Viagra works for you and whether you experience side effects.

Viagra 25mg - A lower strength of Viagra that can be considered if the 50mg dose is not well tolerated or where certain medical conditions or interacting medicines mean a lower dose is more appropriate.

Viagra 50mg - The usual, recommended starting dose of Viagra for most adult men with erectile dysfunction.

Viagra 100mg - The maximum recommended dose of Viagra. It can be considered if the 50mg dose has been well tolerated but has not produced a sufficient response.

Viagra is normally taken as needed, approximately one hour before sexual activity. If the response is insufficient or side effects occur, our prescribing team can review whether a different strength is appropriate.

The maximum recommended dose of Viagra is 100mg and the maximum number of doses per day is one tablet. Taking doses above the recommended maximum intake can increase the likelihood and severity of side effects without providing additional effects.

Do not increase your dose or combine different strengths without consulting with your prescriber.

Viagra is typically taken approximately one hour before sexual activity. In clinical studies, sildenafil (the active ingredient in Viagra) reached its highest blood concentration within around 30 to 120 minutes after taking it when taken without food. Some men can respond sooner and individual responses vary.

A large and/or high-fat meal can delay absorption of Viagra and can make it take longer to work. This is why some men prefer to take it before food or after a lighter meal.

Recommended reading: How Long Does Viagra Take to Kick In?

Viagra typically can help achieve and maintain an erection around four hours after taking a dose, although the strength and duration of the effect vary between individuals and gradually reduce over time.

Clinical studies found that sildenafil could still support an erection in response to sexual stimulation around four to five hours after a dose. It is important to be aware that this does not mean that the effect remains equally strong throughout this period or that you will have an erection continuously for four hours.

Viagra only helps you get or maintain an erection when you are sexually stimulated. Once sexual stimulation has ended, your erection should normally subside.

Never take another Viagra tablet to try to extend the treatment effectiveness window, as the maximum recommended dosing frequency is one tablet per day.

The amount of sildenafil in the body falls gradually after you take Viagra. Sildenafil has a half-life of approximately three to five hours, which means that the amount present in the bloodstream substantially reduces over time.

It is important to be aware that the time sildenafil remains in the body is not the same as the length of its effects on erectile dysfunction.

Certain medicines and/or medical conditions can affect how quickly sildenafil leaves your body, which is why your medical history and current medicines you are taking are reviewed before Viagra is prescribed to you.

Viagra is a well-established treatment for erectile dysfunction, and sildenafil has been extensively studied in clinical trials.

In fixed-dose clinical studies reported in the official Viagra product information, the proportion of men who reported improved erections was:

• 62% with Viagra 25mg
• 74% with Viagra 50mg
• 82% with Viagra 100mg
• 25% with placebo

It is important to be aware that these figures do not mean that a higher dose is automatically the best option for you. The appropriate strength depends on how well the medicine works, how well it is tolerated and your individual medical circumstances, including your medical history and medicines you take.

The effects of Viagra can also vary depending on the underlying cause of erectile dysfunction as well as whether Viagra has been taken correctly, food and alcohol intake, other medicines and psychological factors such as stress or performance anxiety.

For more detailed clinical information, see the official Viagra Summary of Product Characteristics on the electronic Medicines Compendium (eMC). General patient guidance is also available from the NHS guidance on sildenafil.

If taking Viagra did not produce the response and effects you expected, this does not necessarily mean that the medicine will not work for you.

Viagra requires sexual stimulation and will not produce an erection automatically. Factors that can reduce the likelihood of results can also include taking the tablet after a large meal, drinking too much alcohol, not allowing enough time for the medicine to work, stress, anxiety or taking the medicine incorrectly.

If Viagra does not help you to get an erection, or the erection does not last long enough for satisfactory sexual activity, speak to your prescriber. Some patients may need to use sildenafil correctly on multiple separate occasions before deciding whether the treatment is not working for them.

If Viagra has been correctly used on multiple occasions but has not produced sufficient effect, it is recommended to:

• Review the dose: if you have been prescribed 25mg or 50mg dose of Viagra and it has been well tolerated, the prescribing team can consider if a higher strength of Viagra is more appropriate for you
• Check how you take it: allowing sufficient time, avoiding a large meal beforehand and limiting excessive alcohol consumption can improve the likelihood of effects
• Consider a different ED treatment: Tadalafil, Vardenafil and Avanafil (Spedra) are alternative erectile dysfunction treatments that are also PDE-5 inhibitors
• Consider whether other factors are contributing: underlying health conditions, smoking, poor sleep, stress and anxiety can all contribute to the risk of erectile dysfunction

Do not take another Viagra tablet (or any PDE-5 inhibitor) within 24 hours or take more than 100mg in an attempt to get better results.

Recommended reading: Which Erectile Dysfunction Treatment Is Best For Me?

Healthy lifestyle changes can sometimes help improve erectile dysfunction, especially where factors such as excess weight, smoking, alcohol, stress or physical inactivity are contributing to erectile dysfunction. They can also help support your overall cardiovascular health.

The NHS recommends several lifestyle changes that can help erectile dysfunction:

• Lose weight if you are overweight
• Stop smoking
• Eat a healthy, balanced diet
• Exercise regularly
• Try to reduce stress and anxiety
• Drink no more than 14 units of alcohol per week
• Take a break from cycling for a while if you regularly cycle for more than three hours per week

These changes can help improve erectile function over time. However, persistent erectile dysfunction can sometimes be linked to an underlying health condition such as high blood pressure, high cholesterol, diabetes, anxiety or hormonal problems.

If you experience persistent erection problems, speak to your GP or a healthcare professional to assess the potential underlying causes.

For more information, see the NHS guidance on erectile dysfunction.

Viagra is suitable for many adult men with erectile dysfunction, but some medical conditions, medicines and other factors can make Viagra unsuitable. Pharmica also has additional eligibility requirements for prescribing Viagra safely through our online service.

As a result, there are circumstances where we may not be able to prescribe Viagra online, even if sildenafil could potentially be considered following a more detailed assessment with your GP or another healthcare professional. Your suitability will be assessed from the information you provide during the consultation.

Medical conditions that may mean Viagra is not suitable through Pharmica

We will not be able to prescribe Viagra through our online service if you:

• Are under 18 or over 75 years of age
• Have had an allergic reaction or serious side effect from tadalafil, sildenafil, vardenafil, avanafil or another erectile dysfunction medicine
• Have ever had a heart attack
• Have ever had a stroke
• Have unstable angina or angina that occurs during sexual activity
• Have been advised to avoid sexual activity or strenuous exercise, or would have difficulty walking quickly for five minutes because of breathlessness, chest pain, dizziness or another health problem
• Have any heart problem, including angina, chest pain, heart failure, irregular heartbeats, heart attack (myocardial infarction), left-ventricular outflow obstruction, cardiomyopathy or valvular heart disease such as aortic stenosis
• Have very low blood pressure
• Have been diagnosed with high blood pressure or take any medicine to treat high blood pressure
• Have any liver problem
• Have any kidney problem or are on dialysis
• Have experienced sudden loss of vision in one or both eyes, including sight loss caused by poor circulation such as non-arteritic anterior ischaemic optic neuropathy (NAION)
• Have a condition that increases the risk of prolonged erections, such as sickle cell anaemia, leukaemia, multiple myeloma, Peyronie's disease or a previous erection lasting longer than four hours
• Have a bleeding disorder such as haemophilia or an active stomach ulcer
• Have a known hereditary degenerative retinal disorder
• Have galactose intolerance, Lapp lactase deficiency or glucose-galactose malabsorption, as Viagra tablets contain lactose
• Have any serious or unstable medical condition that may require urgent medical attention or hospital care

If you have ever had a heart attack or stroke, Pharmica will not be able to prescribe Viagra through our online service. We recommend speaking to your GP or another healthcare professional who can assess whether treatment may be appropriate following a more detailed medical review.

Medicines and recreational drugs that may affect your suitability for Viagra through Pharmica

Some medicines and recreational substances can interact with sildenafil, the active ingredient in Viagra. Other medicines and substances may require additional assessment or fall within Pharmica's eligibility criteria for online prescribing.

Please tell us during your consultation if you take or use any of the following:

• Other erectile dysfunction medicines or PDE-5 inhibitors, including sildenafil, tadalafil, vardenafil or avanafil, as these need to be reviewed before Viagra can be prescribed
• Medicinal nitrates used to treat chest pain or heart conditions, including glyceryl trinitrate (GTN), isosorbide mononitrate or isosorbide dinitrate
• Nitric oxide donors or recreational nitrates known as “poppers”, including amyl nitrite
• Riociguat, which is used to treat certain forms of pulmonary hypertension
• Alpha-blockers such as doxazosin or tamsulosin, which can increase the risk of symptomatic low blood pressure when combined with sildenafil
• Medicines used to treat high blood pressure or pulmonary hypertension
• Ritonavir or other antiviral medicines used to treat HIV
• Antifungal medicines such as ketoconazole or itraconazole
• Antibiotics such as erythromycin or clarithromycin
• Cimetidine
• Nicorandil
• Rifampicin or other medicines that can reduce sildenafil concentrations in the body
• Bosentan
• St John's Wort or other herbal medicines and supplements that may interact with sildenafil
• Recreational drugs, as these can interact unpredictably with sildenafil and may increase the risk of serious side effects

Your eligibility will be assessed through our online consultation. Our prescribing team will then review your medical history, current medicines and consultation answers before deciding whether Viagra can be prescribed safely through Pharmica.

If we are unable to prescribe Viagra through our online service, this does not necessarily mean that sildenafil is unsuitable for you in every clinical setting. We may recommend that you speak to your GP or another healthcare professional who can consider your individual circumstances in more detail.

Like all medicines, Viagra can cause side effects, although not everyone experiences them and they vary between individuals taking it.

The most commonly reported side effects of sildenafil include headache, facial flushing, indigestion, nasal congestion, dizziness, nausea, hot flushes and temporary visual symptoms such as blurred vision or changes in colour perception.

Stop taking Viagra and seek urgent medical advice if you experience any of the following:

• An erection that lasts longer than four hours (known as priapism) as this can cause permanent damage if it is not treated as soon as possible
• Sudden loss or significant reduction of vision
• Sudden reduction or loss of hearing
• Chest pain, severe breathlessness, fainting or symptoms of a serious heart problem
• A seizure
• Signs of a serious allergic reaction, including swelling of the face, lips, mouth or throat, difficulty breathing or a widespread rash

If you develop an erection that lasts longer than four hours, seek emergency medical treatment immediately.

Official medicine information is available in the Viagra Patient Information Leaflet on the electronic Medicines Compendium (eMC).

You can also report side effects to the MHRA through the Yellow Card Scheme.

Recommended reading: Viagra Side Effects

Viagra and its active ingredient, sildenafil, have an established safety profile when it is prescribed after a medical assessment and is taken according to the recommended dose. The official Viagra safety profile is based on thousands of patients studied in placebo-controlled clinical trials.

However, Viagra is not suitable for everyone and can cause side effects. The most important safety considerations are related to cardiovascular health, blood pressure, as well as other medicines that interact with sildenafil and conditions that increase the risk of prolonged erections or certain eye problems.

Completing the medical consultation allows the prescribing team to assess whether Viagra is appropriate for you.

Some men with high blood pressure may be able to use sildenafil following an appropriate medical assessment. However, Pharmica applies additional eligibility criteria when prescribing Viagra through our online service.

We are unable to prescribe Viagra through Pharmica if you have been diagnosed with high blood pressure or take medicine to treat high blood pressure. If this applies to you, speak to your GP or another healthcare professional who can assess whether sildenafil may be suitable for you in a different clinical setting.

Never stop or change any blood pressure medicine in order to take Viagra unless you have been specifically advised to do so by an appropriate healthcare professional.

The price of Viagra at Pharmica depends on the strength and number of tablets selected:

If you are looking for a cheaper alternative, Generic Sildenafil contains the same active ingredient as branded Viagra and works in the same way as branded Viagra, but is available at a lower cost as it is a generic medicine.

Prescription Viagra in 25mg, 50mg and 100mg strengths is a Prescription-Only Medicine (POM) in the UK. This means it must only be supplied against a valid prescription following an assessment from registered healthcare professionals.

Pharmica is a UK-registered online pharmacy. You can view our General Pharmaceutical Council registration and inspection information for GPhC reference 9012030.

Orders for prescription Viagra are subject to an online consultation questionnaire and review by our UK-based prescribers before treatment can be approved and dispensed.

Viagra was originally developed by Pfizer, and Viatris is the current company that is responsible for the branded Viagra medicine in the UK.

Branded Viagra tablets are blue, rounded, diamond-shaped tablets marked with “Viagra” and the relevant strength code. However, appearance alone cannot confirm that a medicine is genuine, as counterfeit products can imitate legitimate packaging and tablets.

The safest way to get genuine Viagra is through a regulated pharmacy that verifies suitability, supplies treatment against an appropriate prescription and obtains medicines through legitimate pharmaceutical supply chains.

Yes. Branded Viagra in the 25mg, 50mg and 100mg strengths offered by Pharmica is a Prescription-Only Medicine in the UK and requires a valid prescription.

At Pharmica, the prescription is issued after completing our online consultation questionnaire that is then assessed by our UK-based prescriber to check if the treatment is suitable for you.

Recommended reading: Why Do I Need a Prescription to Buy Viagra?

No, prescription Viagra in 25mg, 50mg and 100mg strengths cannot be purchased without a prescription in the UK, as Viagra is classified as Prescription-Only Medicine (POM).

However, Viagra Connect 50mg is classified as a Pharmacy (P) medicine and can be supplied without a prescription following an assessment by a pharmacist. Pharmacy medicines can be supplied through registered high-street pharmacies and regulated online pharmacy services, subject to the required suitability assessment.

If you require Viagra 25mg or 100mg, these strengths are available as prescription Viagra and require an appropriate prescriber assessment and prescription.

Complete a short online consultation covering your erectile dysfunction symptoms, medical history and any other medicines you take.

Our UK-based prescriber will review your answers and, if Viagra is suitable for you, a free prescription will be issued. Your treatment will then be dispensed by our pharmacy team in discreet, plain packaging.

If Viagra is not suitable for you, our prescribing team will explain why and, where appropriate, suggest another treatment or recommend that you speak to your GP or another healthcare professional.

Viagra orders placed through Pharmica are dispatched in plain, discreet packaging once the prescription has been approved, and the medicine has been dispensed by our pharmacy team.

Delivery options can include next-day delivery, Same Day Delivery and Collect Near You options, depending on your location and availability. If collection is available for your order, the available collection option will be shown during the ordering process.

See our delivery information for current options, costs and estimated delivery times.

Watch our patient care expert explain everything you need to know about Viagra.

You can drink alcohol while taking Viagra, but drinking large amounts of it can make it more difficult to get an erection and can reduce the effectiveness of the treatment. Alcohol can also make dizziness or light-headedness worse.

For the most consistent effects, avoid drinking large amounts of alcohol around the time you take Viagra.

For more information, read our detailed guide to Viagra and alcohol.

Yes. Viagra can be taken with or without food, but a large and/or high-fat meal can delay the absorption of sildenafil and make it take longer to work.

If the timing of the effects is important, you can take Viagra before food or after a lighter meal to increase the chance of faster results.

Viagra and Sildenafil contain the same active ingredient, sildenafil citrate, and work in the same way to treat erectile dysfunction (ED).

Viagra is the original branded medicine developed by Pfizer, while Sildenafil is the generic version manufactured by other licensed pharmaceutical companies.

Before a generic sildenafil medicine can be marketed in the UK, it must have an appropriate marketing authorisation and meet the regulatory requirements assessed by the Medicines and Healthcare products Regulatory Agency (MHRA).

For a generic application, the manufacturer must demonstrate that the medicine contains the same active substance, has the same pharmaceutical form as the reference medicine and is bioequivalent to it (which means the generic medicine delivers the active ingredient into the body in a sufficiently comparable way to the reference product).

This allows the generic medicine to rely on the established safety and efficacy evidence for the authorised reference medicine, while the MHRA assesses the generic product against the applicable requirements, including its quality and evidence of bioequivalence, before granting a UK marketing authorisation.

The main differences are branding, tablet appearance, inactive ingredients, packaging and price, where generic Sildenafil is cheaper than branded Viagra.

For a more detailed comparison, read our Viagra vs Sildenafil guide.

Both Viagra and Viagra Connect contain sildenafil, but they differ in how they are supplied and the strengths available.

Prescription Viagra is available in 25mg, 50mg and 100mg strengths and requires a prescription following a clinical assessment to be supplied.

Viagra Connect is a 50mg pharmacy medicine and can be supplied without a prescription following a suitability assessment by a pharmacist.

Viagra and Cialis are both PDE-5 inhibitors used to treat erectile dysfunction, but they contain different active ingredients and have different durations of action.

Viagra contains sildenafil and is generally taken approximately one hour before sexual activity, with effects typically lasting for around four hours. Cialis, on the other hand, contains tadalafil, which can remain effective for up to 36 hours and is also available as a lower-dose daily treatment.

Neither treatment is universally better than the other. The most suitable option depends on factors such as how often you anticipate sexual activity, how you respond to treatment, food interactions, side effects and your medical history.

Read our Viagra vs Cialis guide for a full comparison.

Viagra can be safely ordered online when it is supplied by a legitimate UK-registered pharmacy following an appropriate prescribing assessment.

A regulated service should verify that the medicine is suitable for you, require relevant information about your medical history and current medicines and supply treatment through a registered pharmacy.

Be cautious of websites offering prescription Viagra without any consultation or prescription, as medicines obtained from unregulated sources may be counterfeit, incorrectly dosed or otherwise unsafe.

Viagra is normally taken as needed before sexual activity and should not be taken more than once in any 24-hour period.

Do not begin taking Viagra every day unless this has been specifically discussed with your prescriber. If you anticipate sexual activity frequently, a daily erectile dysfunction treatment such as low-dose Tadalafil can be a more suitable alternative depending on your medical suitability and treatment preference.

Several other treatments are available for erectile dysfunction.

If tablet treatments are unsuitable or do not work adequately, other options can include vacuum erection devices or treatments such as alprostadil following assessment by an appropriate healthcare professional.

If you are unsure which treatment may suit you, read our guide to choosing an erectile dysfunction treatment.

Positive lifestyle changes can improve erectile dysfunction for some men, especially where smoking, excess weight, alcohol, inactivity, stress or other factors are contributing to the problem.

However, products promoted as “Natural Viagra” or herbal erectile dysfunction treatments do not have the same clinical evidence base or regulatory review as licensed medicines such as sildenafil. Some unregulated products may also contain undeclared pharmaceutical ingredients.

Viagra should not be taken at the same time as another PDE-5 inhibitor or erectile dysfunction medicine without specific medical assessment.

Combining Viagra with Sildenafil, Tadalafil, Vardenafil or Avanafil can increase the risk of side effects, including a significant fall in blood pressure, dizziness and prolonged erections.

If Viagra has not worked as expected, contact our prescribing team to discuss changing the strength or switching treatment rather than combining medicines yourself.

Viagra is licensed to treat erectile dysfunction, not premature ejaculation. It can help a man get and maintain an erection when sexually stimulated, but it does not directly delay ejaculation.

Some men with erectile dysfunction can feel more confident or find it easier to resume sexual activity after ejaculation, but this is different from treating premature ejaculation itself.

For more information, read our guide: Can Viagra Help You Last Longer in Bed?

Viagra is not licensed for the treatment of erectile dysfunction in women.

Women experiencing problems with sexual function should speak to their healthcare professional to assess the underlying causes and discuss appropriate treatment or support.

Read more in our guide to Viagra for women.

Taking more Viagra than you have been prescribed can increase the likelihood and severity of side effects and does not necessarily make the treatment more effective.

If you have taken more than your prescribed dose, contact NHS 111 for advice.

Seek urgent medical help if you experience severe symptoms such as chest pain, fainting, a seizure, a serious allergic reaction or an erection lasting longer than four hours.

Keep Viagra out of the sight and reach of children. The branded Viagra product information advises storing the tablets below 30°C and keeping them in the original packaging to protect them from moisture.

Do not use Viagra after the expiry date printed on the packaging. Unwanted or expired medicines should be returned to a pharmacy for safe disposal rather than disposed of through household wastewater.

• Viagra 50mg Summary of Product Characteristics, electronic Medicines Compendium (eMC). Official clinical information covering indications, dosage, contraindications, interactions, clinical efficacy, pharmacokinetics and adverse effects. [Accessed 24 September 2026]
• Viagra 50mg Patient Information Leaflet, electronic Medicines Compendium (eMC). Official patient information for branded Viagra. [Accessed 24 September 2026]
• Viagra Connect 50mg Patient Information Leaflet, electronic Medicines Compendium (eMC). Official patient information for Viagra Connect 50mg. [Accessed 24 September 2026]
• NHS: Sildenafil (Viagra). NHS guidance on taking sildenafil, suitability, side effects, interactions, food and alcohol. [Accessed 24 September 2026]
• NHS: Erectile dysfunction. NHS guidance on causes, lifestyle measures and treatment of erectile dysfunction. [Accessed 24 September 2026]
• General Pharmaceutical Council: Pharmica, GPhC reference 9012030. Pharmacy registration and inspection information. [Accessed 24 September 2026]
• MHRA Yellow Card Scheme. UK service for reporting suspected medicine side effects and safety concerns. [Accessed 24 September 2026]
• MHRA: Types of application for marketing authorisations. MHRA guidance on UK marketing authorisation applications, including the regulatory requirements for generic medicines and demonstrating bioequivalence to a reference medicine. [Accessed 25 September 2026]
• MHRA: 20 million illegal erectile dysfunction pills seized as MHRA warns against risky online buys. MHRA guidance and safety information on the risks of buying unauthorised erectile dysfunction medicines, including counterfeit and illegally supplied products. [Accessed 25 September 2026]