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Viagra (Sildenafil)

Viagra (Sildenafil)

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  • ✔️ Clinically proven to treat erectile dysfunction in adult men
  • ✔️ Works within 30–60 minutes of taking a single tablet
  • ✔️ Effective for up to 4–5 hours per dose
  • ✔️ Suitable for men with physical or psychological causes of ED
  • ✔️ Available in 25 mg, 50 mg, and 100 mg strengths

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What Are Sildenafil Tablets UK Used For?

 

Erectile dysfunction (ED) is more common than many men realise. In fact, it affects around one in five men in the UK at some point in their lives, and the numbers rise significantly with age. If you struggle to get or keep an erection firm enough for sex, you are far from alone — and there are clinically proven options available. Sildenafil tablets UK are one of the most widely used and well-studied treatments for ED, available from Cured Pharmacy following a short clinical assessment. You can also explore our wider range of products in our men's health collection.

Sildenafil is the active ingredient in the branded medicine Viagra, which has been licensed in the UK since 1998. The generic version became available in 2013, making effective ED treatment more accessible. At Cured Pharmacy, sildenafil is available from £37.95, dispensed by our GPhC-registered superintendent pharmacist.

 

How Does Viagra (Sildenafil) Work in the Body?

 

Sildenafil belongs to a class of medicines called phosphodiesterase type 5 (PDE5) inhibitors. It works by blocking the PDE5 enzyme, which normally breaks down a chemical called cyclic guanosine monophosphate (cGMP). When cGMP accumulates, the smooth muscle in the walls of penile blood vessels relaxes, allowing more blood to flow in. The result? A firmer, more sustained erection — but only when you are sexually stimulated. Sildenafil does not cause an erection on its own.

  • Sexual stimulation triggers the release of nitric oxide in penile tissue
  • Nitric oxide activates an enzyme that produces cGMP
  • cGMP relaxes smooth muscle and dilates blood vessels in the penis
  • Sildenafil prevents PDE5 from breaking down cGMP, prolonging the effect
  • Increased blood flow produces and maintains an erection

 

Who Is Suitable for Viagra (Sildenafil) Treatment?

 

Sildenafil is licensed for adult men (aged 18 and over) with erectile dysfunction. It is suitable whether your ED has a physical cause — such as diabetes, high blood pressure, or cardiovascular disease — or a psychological one, such as anxiety or stress. That said, it is not appropriate for everyone, and a clinical assessment is always required before dispensing.

  • Adult men aged 18 and over with diagnosed or suspected ED
  • Men whose ED has a physical or psychological cause
  • Men who are not taking nitrate medicines for chest pain
  • Men without severe cardiovascular, hepatic, or renal impairment

 

How Does Viagra (Sildenafil) Compare to Other ED Treatments?

 

Feature Sildenafil (Viagra) Tadalafil (Cialis)
Onset of action 30–60 minutes 30–60 minutes
Duration of effect Up to 4–5 hours Up to 36 hours
Affected by food Yes — high-fat meals delay absorption Minimal effect
Available as generic Yes Yes

 

How Should You Store Sildenafil Tablets?

 

Store your sildenafil tablets UK below 30°C in a dry place, away from direct sunlight and out of reach of children. Do not use the tablets after the expiry date printed on the packaging. If you are unsure whether your tablets are still suitable to use, speak to your pharmacist. For those managing other health conditions alongside ED, you may find our vitamins and supplements collection a useful complement to your overall health routine.

This product is a medicine. Speak to your doctor or pharmacist before using if you have an underlying medical condition or are taking other medicines.

Viagra (Sildenafil) specifications
Treatment category Erectile dysfunction
Active ingredient Sildenafil citrate
Mechanism of action PDE5 inhibitor — increases blood flow to the penis
Strengths 25 mg, 50 mg, 100 mg
Pack sizes 4, 8, 16 tablets (varies by supplier)
UK classification Prescription-only medicine (POM) / Pharmacy (P) for 50 mg OTC
Drug class Phosphodiesterase type 5 (PDE5) inhibitor
Preparation Film-coated tablet
Route of administration Oral
Suitable for Adult men aged 18 and over
Effective Within 30–60 minutes of taking

Specifications of Viagra (Sildenafil)

 

What Is Viagra (Sildenafil) and What Is It Used For?

 

Viagra (sildenafil) is a prescription-strength medicine used to treat erectile dysfunction in adult men. It belongs to the PDE5 inhibitor class of medicines and works by improving blood flow to the penis during sexual stimulation. It does not increase sexual desire and will not produce an erection without arousal. Sildenafil has been licensed in the UK for over two decades and has an extensive safety record when used correctly.

 

What Do You Need to Know Before Using Viagra (Sildenafil)?

 

Before taking sildenafil, it is essential to tell your doctor or pharmacist about all medicines you are currently taking and any health conditions you have. Some combinations can be dangerous.

Do not take sildenafil if you:

  • Are taking nitrate medicines (e.g. glyceryl trinitrate, isosorbide mononitrate) for chest pain or heart problems
  • Are taking riociguat or other soluble guanylate cyclase stimulators
  • Have severe liver disease
  • Have recently had a stroke or heart attack
  • Have low blood pressure (hypotension) or uncontrolled high blood pressure
  • Have a rare inherited eye condition such as retinitis pigmentosa
  • Are under 18 years of age

Known drug interactions — tell your pharmacist if you take:

  • Alpha-blockers (e.g. doxazosin, tamsulosin) — risk of low blood pressure
  • HIV protease inhibitors (e.g. ritonavir, saquinavir) — increase sildenafil levels in the blood
  • Antifungals such as ketoconazole or itraconazole
  • Other PDE5 inhibitors (e.g. tadalafil, vardenafil)
  • Erythromycin or cimetidine

 

How Should You Use Viagra (Sildenafil) Correctly?

 

  1. Take one tablet approximately 30 to 60 minutes before planned sexual activity
  2. Swallow the tablet whole with a glass of water
  3. Avoid high-fat meals before taking — they can delay how quickly the medicine works
  4. Sexual stimulation is required for the medicine to be effective
  5. Do not take more than one tablet in any 24-hour period
Indication Age Group Dose Frequency
Erectile dysfunction Adults (18–64) 50 mg (starting dose); may adjust to 25 mg or 100 mg Once daily maximum
Erectile dysfunction (elderly or hepatic/renal impairment) 65 and over 25 mg starting dose Once daily maximum

 

What Are the Possible Side Effects of Viagra (Sildenafil)?

 

Like all medicines, sildenafil can cause side effects, though not everyone experiences them. Most side effects are mild and short-lived. If you experience chest pain, a sudden loss of vision, or an erection lasting more than 4 hours (priapism), seek emergency medical attention immediately. You can also browse our condoms and sexual health collection for additional support products.

Common side effects (may affect up to 1 in 10 people):

  • Headache
  • Facial flushing (redness and warmth)
  • Indigestion or upset stomach
  • Nasal congestion
  • Dizziness
  • Visual disturbances (blurred vision, colour tinge)

Less common side effects (may affect up to 1 in 100 people):

  • Palpitations
  • Nausea
  • Skin rash
  • Muscle pain
  • Prolonged erection (priapism) — seek urgent help if erection lasts over 4 hours
  • Sudden hearing loss or tinnitus

 

How Should You Store Viagra (Sildenafil) Safely?

 

  • Store below 30°C in a dry place away from direct sunlight
  • Keep in the original packaging until use
  • Keep out of the sight and reach of children
  • Do not use after the expiry date printed on the pack
  • Do not dispose of medicines via wastewater or household waste — return unused tablets to your pharmacy

If you are managing other aspects of your health alongside ED treatment, our pain relief collection may be helpful for any associated discomfort.

Written and reviewed by our qualified team

Your safety and success are our highest priorities. Our medical team rigorously evaluates every product and piece of advice we provide, ensuring you receive only the most effective, science-backed solutions available.

Frequently Asked Questions

Where can I buy Viagra (sildenafil) online in the UK?

You can buy sildenafil tablets UK from Cured Pharmacy, a GPhC-registered online pharmacy. A short clinical questionnaire is completed before dispensing to confirm the medicine is safe and appropriate for you. This ensures you receive genuine, regulated medication with full pharmacist oversight.

How does Viagra (sildenafil) work in the body?

Sildenafil inhibits the PDE5 enzyme, which normally breaks down cGMP in penile smooth muscle tissue. When cGMP levels remain elevated, blood vessels in the penis relax and widen, allowing increased blood flow during sexual stimulation. It is important to understand that sildenafil only works when you are sexually aroused — it does not create an erection independently.

How long does Viagra (sildenafil) take to work?

Sildenafil typically begins to work within 30 to 60 minutes of taking it orally. The effect can last up to 4 to 5 hours, though this varies between individuals depending on factors such as age, metabolism, and whether a high-fat meal was eaten beforehand. Taking it on an empty stomach or after a light meal tends to give the fastest onset.

What is the correct dose of Viagra (sildenafil) for me?

The standard starting dose is 50 mg, taken approximately one hour before sexual activity. Depending on how well it works and how well you tolerate it, your doctor or pharmacist may recommend adjusting to 25 mg or 100 mg. Never take more than one dose in a 24-hour period.

What are the most common side effects of Viagra (sildenafil)?

The most frequently reported side effects include headache, facial flushing, nasal congestion, and indigestion. These are usually mild and resolve on their own within a few hours. If you experience chest pain, sudden vision loss, or an erection lasting more than 4 hours, seek emergency medical attention immediately.

Can I take Viagra (sildenafil) with alcohol?

Drinking alcohol alongside sildenafil can increase the risk of side effects such as dizziness, low blood pressure, and headache. It is advisable to limit alcohol intake when using this medicine. Excessive alcohol can also independently worsen erectile dysfunction, so moderation is sensible for both reasons.

Who should not take Viagra (sildenafil)?

Sildenafil must not be taken by anyone using nitrate medicines for chest pain, as the combination can cause a dangerous and potentially life-threatening drop in blood pressure. It is also not suitable for men with severe liver disease, recent stroke or heart attack, or those under 18 years of age. Always complete a clinical assessment before starting treatment.

How do I manage side effects of Viagra (sildenafil)?

Most side effects such as headache or flushing are mild and short-lived, and can often be managed by staying well hydrated and resting. If indigestion is a problem, try taking the tablet with a light meal rather than on an empty stomach. For persistent or severe side effects, speak to your pharmacist or GP — they may suggest a dose adjustment.

What are the alternatives to Viagra (sildenafil)?

Other licensed PDE5 inhibitors available in the UK include tadalafil (Cialis), vardenafil (Levitra), and avanafil (Spedra). Tadalafil is notable for its longer duration of action — up to 36 hours — making it a popular alternative for men who prefer more spontaneity. You can explore related products in our condoms and sexual health collection.

Does Viagra (sildenafil) work the first time you take it?

Sildenafil works for many men on the first attempt, but some men find it takes two or three tries before they notice the full benefit — particularly if anxiety is a contributing factor. If it does not seem to work initially, try taking it on an empty stomach and ensure you allow adequate time for sexual stimulation. If it consistently fails to work, speak to your GP.

Can I take Viagra (sildenafil) every day?

The standard formulation of sildenafil is intended to be taken as needed, not as a daily routine medicine. You should not take more than one dose in any 24-hour period. If you are looking for a daily ED treatment option, tadalafil 5 mg is licensed for daily use — speak to your GP or pharmacist about whether this might suit you better.

How long can you keep taking Viagra (sildenafil)?

There is no fixed maximum duration for sildenafil use, and many men take it safely over the long term. However, it is good practice to review your treatment periodically with your GP, particularly if your underlying health conditions change. Erectile dysfunction can sometimes be a sign of cardiovascular disease, so ongoing medical review is worthwhile.

Is Viagra (sildenafil) safe if I have high blood pressure?

Sildenafil can be used by some men with high blood pressure, but it requires careful assessment — particularly if you are taking antihypertensive medicines, as the combination can lower blood pressure further. Alpha-blockers in particular can interact with sildenafil. Always disclose your full medication list to your pharmacist or GP before starting treatment.

What are the latest studies on Viagra (sildenafil)?

Beyond erectile dysfunction, sildenafil is also licensed for pulmonary arterial hypertension under the brand name Revatio. Ongoing research has explored potential benefits in areas such as heart failure and altitude sickness, though these remain outside its licensed indications in the UK. For ED specifically, sildenafil remains one of the most extensively studied oral treatments available. You can find further general men's health information in our men's health collection.

What happens if I miss a dose of Viagra (sildenafil)?

Because sildenafil is taken as needed rather than on a fixed daily schedule, a missed dose simply means you did not take it before a particular occasion. There is no need to double up or take an extra dose to compensate. Just take it as planned the next time you intend to be sexually active, following the usual instructions.

How Should You Use Viagra (Sildenafil)?

Sildenafil is taken orally as a film-coated tablet. Always follow the instructions given by your pharmacist or doctor, and read the patient information leaflet supplied with your medicine before use. Taking it correctly gives you the best chance of it working well.

What Is the Correct Dose of Viagra (Sildenafil)?

The recommended starting dose for most adult men is 50 mg. Your doctor or pharmacist may adjust this based on how effective it is and how well you tolerate it. The lowest effective dose should always be used.

When Is the Best Time to Use Viagra (Sildenafil)?

Take sildenafil approximately 30 to 60 minutes before you plan to be sexually active. Some men find it works best when taken on an empty stomach or after a light, low-fat meal, as high-fat foods can delay how quickly the medicine is absorbed into the bloodstream. There is no single "best" time of day — it simply depends on when you plan to use it.

Avoid taking it more than 4 hours before sexual activity, as the effect may begin to diminish. Alcohol should be limited around the time of taking sildenafil, as it can increase the risk of side effects and may independently worsen erectile function.

How Long Can You Use Viagra (Sildenafil) For?

Sildenafil can be used on an ongoing, as-needed basis for as long as it remains appropriate for you. There is no set maximum treatment duration, and many men use it safely over months or years. However, it is important to have periodic reviews with your GP, particularly if your health circumstances change or if you develop new medical conditions.

Erectile dysfunction can sometimes indicate an underlying cardiovascular condition, so regular health checks are worthwhile. If sildenafil stops working as well as it did initially, speak to your doctor rather than simply increasing the dose yourself.

Do not exceed the recommended dose. If in doubt, speak to your pharmacist.

What Are the Most Common Side Effects of Viagra (Sildenafil)?

Most men who take sildenafil tolerate it well, but like all medicines, it can cause side effects. Common side effects affect up to 1 in 10 people and are usually mild and temporary, resolving within a few hours without any treatment.

  • Headache
  • Facial flushing (redness and warmth in the face)
  • Indigestion or stomach discomfort
  • Nasal congestion or a runny nose
  • Dizziness
  • Visual disturbances, including blurred vision or a blue-green colour tinge

What Are the Less Common Side Effects of Viagra (Sildenafil)?

Less common side effects affect fewer people but are still worth being aware of. If any of the following persist or become troublesome, contact your pharmacist or GP for advice.

  • Palpitations or awareness of your heartbeat
  • Nausea
  • Skin rash or itching
  • Muscle aches or back pain
  • Dry mouth
  • Tinnitus (ringing in the ears)
  • Sudden decrease or loss of hearing

What Are the Serious Side Effects of Viagra (Sildenafil)?

Serious side effects are rare but require immediate medical attention. Do not ignore these symptoms or wait to see if they resolve on their own.

Seek emergency help immediately if you experience:

  • Chest pain or tightness — particularly during or after sexual activity
  • A prolonged erection lasting more than 4 hours (priapism) — this can cause permanent damage if untreated
  • Sudden loss of vision in one or both eyes
  • Severe allergic reaction — swelling of the face, lips, tongue, or throat, difficulty breathing
  • Sudden severe drop in blood pressure — feeling faint, lightheaded, or collapsing

What Should You Do If You Experience Side Effects of Viagra (Sildenafil)?

For mild side effects such as headache or flushing, staying hydrated and resting usually helps. If indigestion is a problem, try taking the tablet with a light meal. If side effects are persistent, bothersome, or you are concerned about any symptom, stop taking the medicine and speak to your pharmacist or GP promptly.

You can also report suspected side effects directly to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk. This helps improve medicine safety for everyone.

Can Viagra (Sildenafil) Interact With Other Medicines?

Yes — sildenafil has several clinically significant interactions. The most dangerous is with nitrate medicines (used for chest pain), which can cause a severe and potentially life-threatening drop in blood pressure. Alpha-blockers, HIV protease inhibitors, certain antifungals, and other PDE5 inhibitors can also interact with sildenafil, either increasing its blood levels or amplifying its blood pressure-lowering effect.

Always tell your pharmacist or doctor about every medicine you are taking — including over-the-counter products, herbal remedies, and supplements — before starting sildenafil.

If you are concerned about any side effects, contact your pharmacist or GP immediately.

Frequently Asked Question

Normally, it kicks in by the half hour to hour mark, depending on your metabolism and whatyou’veeaten. Onceit’sactive, the effects can last for upto 4 hours allowing you to have and achieve strong, lasting erection.

Viagra should not be taken more than once in 24 hours. If you require more frequent treatment, speak to your pharmacist — they may suggest an alternative like daily Tadalafil.

No. Viagra should never be combined with other ED treatments or nitrates, as this can cause dangerous drops in blood pressure.

Keep them in their original packaging, stored below 30°C, and away from moisture or direct sunlight. Always keep them out of reach of children.

Patient Information Leaflet

Important - Before taking any medication, it is always important to read the Patient Information Leaflet (PIL)

Written and reviewed by our qualified team

GPhC Number: 2233073
Tarun Kumar

Reviewed by:

Tarun Kumar

Superintendent/ Clinical Lead

📖 Find out more about our team of medical content authors and how we ensure the accuracy of our content with our content guidelines.

Content last updated: 31 Mar 2025

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How fast does Cialis start working?

Normally, it kicks in by the half hour to hour mark, depending on your metabolism and whatyou’veeaten. Onceit’sactive, the effects can last for upto 4 hours allowing you to have and achieve strong, lasting erection.

Is it safe to take Viagra every day?

Viagra should not be taken more than once in 24 hours. If you require more frequent treatment, speak to your pharmacist — they may suggest an alternative like daily Tadalafil.

Can I use Viagra with other ED medications?

No. Viagra should never be combined with other ED treatments or nitrates, as this can cause dangerous drops in blood pressure.

How should I store Viagra tablets?

Keep them in their original packaging, stored below 30°C, and away from moisture or direct sunlight. Always keep them out of reach of children.