Viagra (sildenafil) tablets to treat erectile dysfunction available to buy online in 25mg, 50mg, and 100mg strengths.

  • Works in 30 to 60 minutes
  • Lasts for 4 hours
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Buy Viagra online

  1. Read medical information about erectile dysfunction
  2. Answer medical questions to check for eligibility
  3. Reviewed by doctors - medication posted from UK pharmacy (tracked 24hr service)

All men with ED should consult their doctor before obtaining erectile dysfunction medication online.

Generic Viagra also available

Lower cost generic Viagra, called sildenafil, has been available since Viagra's patent expired in the UK in June 2013. Sildenafil citrate is the medical name of the active ingredient in Viagra. Generic Viagra tablets cost from 95p each - branded Viagra cost £5.


Prices of Viagra and sildenafil erectile dysfunction medication (in stock)
Tablet type4 tablets8 tablets16 tablets32 tablets64 tablets
Sildenafil 25mg£5.95£12.95£22.95£42.95£60.95
Sildenafil 50mg£8.45£13.95£23.95£44.95£60.95
Sildenafil 100mg£9.25£15.95£28.40£54.00n/a
Viagra 25mg£24.20£44.30£82.00n/an/a
Viagra 50mg£29.40£59.50£112.60n/an/a
Viagra 100mg£33.80£64.45£124.50n/an/a

Price match guaranteePrice match guarantee
Prescription issued online - small prescription fee per order.

Compare prices: Dr Fox prices are 25%-50% lower cost than other online clinics.

Prescription fees

Dr Fox supplies medicine on prescription and charges a small prescription fee based on the order value of each prescription.

Prescriptions are issued by our doctors online and sent electronically to our pharmacy.

If you have your own private paper prescription please post to our pharmacy (details).

Dr Fox prices are 25%–50% lower than other UK online clinics.

Order valuePrescription fee
up to £10£1.00
up to £20£2.00
up to £40£3.00
over £40£4.00
Compare prices from UK online clinics (07 October 2019) - qualifying notes
*Dr Fox adds a small prescription fee not included in table above.
  1. The prices shown are listed by the online clinics named after a customer first enters consultation information and is offered prescriptions. It is possible these clinics may have special offers or lower prices for repeat supplies.
  2. Prices may change and are, to the best of our knowledge, accurate on the date stated. All products in stock and new condition.
  3. Dr Fox does NOT claim to provide a superior service to any of the online clinics listed. All the clinics listed, as far as we can tell, comply with all regulation and, as far as we can tell, operate to high ethical standards.
  4. Dr Fox adds a small prescription fee not included in the table (between £1 and £4 depending on value of the order).
  5. To amend the information in this table please contact us
  6. The prices listed in the table do not identify the cost of prescription medicine as online clinics charge a single fee to cover services which includes advice, consultations, prescriptions, and dispensing and supply of treatments.
  7. Where services include free delivery this is using the slowest delivery option available. Dr Fox uses Royal Mail Tracked 24.
Generic/BrandedDr Fox*Simple Online PharmacyZavamedPharmicaMed Express
Generic 25mg x 4£5.95£7.95£9.95£9.99£9.99
Generic 25mg x 8£12.95£14.95£17.00£19.99£19.99
Generic 25mg x 16£22.95£26.95£35.00£34.99£39.99
Generic 25mg x 32£42.95£47.99n/a£53.99£79.99
Generic 50mg x 4£8.45£9.75£12.00£23.00£14.99
Generic 50mg x 8£13.95£17.99£19.00£38.00£26.99
Generic 50mg x 16£23.95£27.95£36.00£60.00£44.99
Generic 50mg x 32£44.95£53.95n/a£86.00£80.99
Generic 100mg x 4£9.25£9.95£17.00£27.00£14.99
Generic 100mg x 8£15.95£16.99£26.00£56.00£29.99
Generic 100mg x 16£28.40£25.99£45.00£75.00£49.99
Generic 100mg x 32£54.00£49.95n/a£130.00£89.99
Viagra 25mg x 4£24.20£24.95£25.00£32.50£29.99
Viagra 25mg x 8£44.30£43.95£48.00£50.00£59.99
Viagra 25mg x 16£82.00£81.95£82.00£95.00£119.99
Viagra 50mg x 4£29.40£29.95£36.00£30.00£34.99
Viagra 100mg x 4£33.80£33.50£39.00£40.00£34.99
Viagra 100mg x 8£64.45£63.95£62.00£60.00£69.99
UK Delivery£2.90£3.20included£3.45£2.90

Delivery charges

UK delivery only: £2.90 per consultation via Royal Mail 24 Signed For (1-3 working days with tracking).

Parcel forwarding services are not permitted. Use only UK home or work delivery address.

Returns and refunds - unwanted items can be returned within 14 working days for a full refund.

About Viagra

  • Viagra is a prescription-only medicine used to treat erectile dysfunction (ED) in men.
  • 'Viagra' is a brand name, the active ingredient is 'sildenafil'.
  • Starting dose is one 50mg tablet in 24 hours. Depending on results, adjust to 25mg or 100mg.
  • Take 30-60 minutes before sexual activity, usually lasts for 4 hours.
  • Read the patient leaflet for a full list of side effects, cautions, and interactions with other drugs.
  • Large meals, fatty food, alcohol, and grapefruit can affect efficacy.
  • Patent expired 2013 in the UK - lower cost generic sildenafil available.

How does Viagra work?

Viagra works by increasing blood flow to the penis which helps men get and sustain an erection long enough for sex.

The active ingredient in Viagra is sildenafil, which is known medically as a PDE5 inhibitor. Sildenafil inhibits (blocks) an enzyme which regulates blood flow in the penis. PDE5 inhibitors multiply the natural process of arousal and increase blood flow to the penis in situations of sexual stimulation. Sildenafil helps to achieve an erection but relies on natural arousal as a trigger. It, and other PDE5 inhibitors such as tadalafil, vardenafil, and avanafil, support sexual relations when erections are failing.

How to take

The usual first starting dose of Viagra is one 50mg tablet, for men who have not used it before, although men over the age of 65 years would normally start on the lowest dose tablet (25mg).

Viagra works in 30 to 60 minutes after it is taken and usually remains active for 4 hours.

If 50mg strength of tablet is highly effective subsequent doses may be reduced down to one 25mg tablet. If a 50mg tablet is ineffective, or the duration of activity is less than 4 hours, the dose can be increased to one 100mg tablet. Do not take Viagra more than once per day, or more than 100mg dose.

Arousal is required for the treatment to work. Viagra is most likely to be suitable if taken in situations where sexual arousal is expected within an hour or two of taking the tablet. Without sexual arousal there will be no benefit and the effect of the tablet will simply wear off after about 4 hours.

Avoid large meals, meals high in fat, excessive alcohol, and grapefruit as these can affect efficacy (effectiveness).


photo of Viagra 25mg pack

Viagra 25mg

Reduced dose recommended when 50mg starting dose is highly effective.

photo of Viagra 50mg pack

Viagra 50mg

Starting dose usually recommended for most men taking Viagra for the first time.

photo of Viagra 100mg pack

Viagra 100mg

Strongest dose pill for when 50mg is ineffective.

Do not take more than 1 dose or more than 100mg in 24 hours, or combine with other erectile dysfunction drugs.

Does it work every time?

A trial of erectile dysfunction medication should be repeated at least 4 times before deciding whether Viagra is working and before requesting a change of dosage or change to another ED medication. As with any treatment, there are times when ED tablets might not work and may not improve or overcome the underlying cause of erectile dysfunction.

Satisfactory erections require the following:

  • Adequate blood supply
  • Arousal
  • Healthy nervous system

If erectile dysfunction is the result of spinal injury or operation, nerves might be damaged. In this case Viagra may help a little but other measures, such as injections or stiffening aids, may be required.

Other causes of erectile dysfunction may require specialist treatment apart from tablets. Some men, whose erectile dysfunction has psychological causes, may benefit from counselling.

The clinical study data reports the following results:

Viagra (sildenafil) dosageMen reporting improved erections

Are there any side effects?

Viagra is remarkably well tolerated and free from significant side effects in the vast majority of men who take it. Viagra increases blood flow which can have adverse affects on other parts of the body, although these are usually mild. Most men who experience side effects carry on treatment regardless.

Slightly over 1% of men taking Viagra notice a bluish or yellowish discolouration of their vision. This is not in itself a cause for concern, and usually does not interfere with normal activity. It wears off after a few hours.

The most commonly reported adverse reactions in clinical studies were:

  • Headache - very common and can be treated with simple painkillers such as paracetamol.
  • Flushing (redness of the skin, typically over the cheeks or neck).
  • Indigestion (dyspepsia) - can be treated with indigestion remedies.
  • Visual disorders/distortion.
  • Nasal congestion - can be treated with menthol or eucalyptus inhalers.
  • Dizziness - if affected it is recommended not to drive or operate machinery.

In the rare event of serious side effects seek immediate medical advice. This applies particularly to chest pains (possibly heart attack), loss of vision, and a prolonged and painful erection.

Priapism is the medical name for prolonged painful erections which have the potential to cause permanent damage to the penis. Priapism is rare. A persistent and painful erection of more than 2 hours requires immediate emergency medical attention.

The full range of side effects is also listed in the patient information leaflet supplied with the tablets.


During the assessment process with Dr Fox men are required to complete an erectile dysfunction questionnaire to determine suitability.

Men with the following conditions should not take Viagra without further assessment from their GP:

  • Taking medicines called nitrates (often given for chest pain)
  • Taking or intend to take amyl nitrite ('poppers')
  • Taking riociguat (to treat high blood pressure in the lungs)
  • Low or high blood pressure
  • Allergies or reactions to past ED treatments
  • Recent heart attack (within 6 weeks) or suffer from angina (heart pain on exertion) or any form of heart disease
  • History of strokes or mini-strokes (transient ischaemic attack)
  • History of vision problems caused by circulation problems
  • History in the family of rare degenerative eye disease
  • Serious kidney (renal) or liver disease
  • Peyronie's disease – angulation or deformity of the penis
  • Leukaemia, multiple myeloma or sickle cell disease
  • Bleeding disorders (such as haemophilia)
  • Current active stomach ulcers (peptic ulcer or gastric ulcer)
  • Lactose intolerant (tablets contain lactose)

Dr Fox cannot supply ED treatment to men who have any of the above conditions.

Recreational misuse

Viagra is sometimes used for recreational rather than therapeutic purposes. If taken in this way, particularly in combination with non-prescribed drugs, there is an increased risk of significant side effects, some of which may be serious.

Patient Information Leaflet

Illustration of patient leaflet from medicine packet

The Patient Information Leaflet (PIL) is the leaflet included in the pack with a medicine and must be read before taking the medicine. It is written for patients and gives information about taking or using a medicine.

Viagra patient leaflet

Viagra Connect

Viagra - the little blue pill recognised across the world - changed the face of erectile dysfunction treatment when it was launched by Pfizer in 1998. With its relatively few side effects, ease of use and proven effectiveness, it is little wonder the drug has become so popular.

Viagra Connect

Viagra was under patent protection in the UK until June 2013, after which legal cheaper versions have been made available under its medical name sildenafil.

In November 2017 the UKs medicines regulator, the MHRA, approved an application by Pfizer to reclassify its sildenafil 50mg to a 'P' medicine (available without prescription) which is sold as a new product called Viagra Connect.

Alternative treatment

Other oral ED drugs work in a similar way, with similar side effects. Viagra was the first drug in this class to become widely prescribed.

The following oral tablet treatments for ED and are available to buy online in various strengths and pack sizes from Dr Fox after completing the same medical consultation:

Other treatments for ED include topical applications, injections into the penis, surgical devices, penis pumps, and counselling.

Why do men get erectile dysfunction?

Many factors can contribute to erectile dysfunction (also known as impotence). Lifestyle choices, such as excessive drinking, smoking, illegal drug use, as well as obesity and stress, can all have an impact on erections. Erectile dysfunction can also be a symptom of underlying health problems such as atherosclerosis (narrowing of the arteries), heart disease, and diabetes, amongst others.

Men suffering from erectile dysfunction should inform their GPs who will undertake an assessment, possibly perform tests, and provide advice. GPs are trained to deal with ED and are sympathetic to any embarrassment it may cause.

See erectile dysfunction medical information for further details.

Further reading

Viagra FAQs

Do Viagra tablets become less effective over time?

Not usually. Studies show men usually find the same dose will be effective over a period of years. The body does not get used to the medicine. ED tends to be a slowly progressive condition, increasing with age, however unless there is an underlying medical progression the same dose should produce the same effect.

What is the difference between Viagra and sildenafil?

The main difference is the name. Viagra is a brand name for sildenafil. Medically they are the same, having the same active ingredient, the medical name of which is sildenafil. Both come in packs of 4 and 8 tablets and in strengths of 25mg, 50mg, and 100mg. Sildenafil is usually much lower cost because it is produced by numerous competing drug companies. Branded Viagra is produced only by Pfizer.

What is the difference between Viagra, Cialis, and Levitra?

The main difference is their duration of action: Viagra (sildenafil) works for about 4 hours; Levitra (vardenafil) for 4-5 hours; and Cialis (tadalafil) for about 36 hours. Each of these medicines work in the same way, by changing the blood flow in the penis, and side effects are similar. Some men find one works better for them than another, although most men find each one equally effective, but for different durations. Men can choose which tablet they use depending on the time they expect to be sexually active. An erection will only occur in the presence of arousal, and without it the treatment remains inactive.

Can I get Viagra on the NHS?

NHS GPs can prescribe sildenafil, although usually do so in limited quantities (1 per week) and will not prescribe branded Pfizer Viagra due to cost. NHS prescription fees apply. See Sildenafil on the NHS.

Can my regular doctor give me a private prescription for Viagra?

Most doctors will be able to prescribe Viagra privately, although they will make a charge for this, usually around £8-£15 per prescription. Online services are nearly always lower cost. Since April 2018 Viagra Connect (sildenafil 50mg) has been available from pharmacies without prescription.

Can I split tablets?

Viagra tablets are scored and can be broken in two. This may be a more cost effective way of using the treatment as the cost of the tablets is not proportional to the amount of active ingredient. A 100mg tablet does not usually cost twice as much as a 50mg tablet. If you find a 50mg tablet is effective, then half a 100mg will be just as good, as will two 25mg tablets. It is the overall amount of active ingredient which matters. 25mg tablets (the lowest dose available) should not be cut in half. The remaining half-tablet should be wrapped in eg clingfilm to prevent it drying out, if not used within a few days.

Dividing tablets is common practice - it is recommended to use a pill cutter for optimum results.

Can ED oral treatments be combined?

No. The commonly used ED oral treatments all work in the same way. Using more than one at the same time will not make treatment more effective, and risks overdose and unwanted side effects. Leave a gap between using one type of treatment and another of at least 24 hours (36 hours for Cialis/tadalafil).

Why shouldn't I drink alcohol when taking Viagra?

It is recommended not to drink alcohol or only a minimal amount of no more than one or two units. Alcohol increases symptoms of erectile dysfunction. There is no direct chemical interaction between sildenafil and alcohol, however the risk of side effects such as a drop in blood pressure and even fainting will increase when used after heavy drinking. The treatment may also be less effective.

Why should men with ED consult their regular doctors before using ED treatment?

ED can be a sign of an underlying medical condition, such as reduced circulation, diabetes, high cholesterol, or a neurological or hormonal issue. These things need to be assessed by a doctor face-to-face, which may include tests, and men taking ED tablets should have check-ups periodically. It is safe to obtain Viagra online from UK regulated pharmacies, however proper diagnosis and review are required.

Can stress cause ED?

Yes, particularly stress in a relationship or around sexual activity can cause erections to fail. Erections are usually stronger in men who are relaxed, rested, and comfortable with their partners. Counselling can be effective for some men who have ED, particularly younger men who have no underlying physical cause of their ED.

What are the risks of taking Viagra with recreation or illegal drugs?

Men taking ED tablets and drugs at the same time are open to numerous risks, from impulsive unsafe behaviour, excessive dosing, and increased side effects, to the serious and potentially irreversible damage caused by the rare condition of priapism. Priapism is a painful erection lasting more than 2 hours which can cause permanent damage to your penis if not treated quickly. There is an increased risk of priapism when Viagra is taken with cocaine.

ED tablets should not be taken with amyl nitrate ('poppers') as the combination can lead to a dangerous fall in blood pressure.

See beware club drugs and Viagra.

Why does the cost of ED treatment vary so much?

Pharmacies providing medicine on private prescriptions are free to charge what they choose. Some pharmacies will charge higher prices and make bigger profits, others may choose lower prices in the expectation that men will return when buying repeat supplies.

Dr Fox provides ED treatment online at a lower cost than other UK regulated pharmacies on the internet (see price comparison table above).

Is Viagra still prescription only medicine?

Yes, Viagra is obtained legally in the UK only if a doctor writes a prescription for it and a registered pharmacy dispenses it. When it is ordered online an electronic prescription is involved. The only exception applies where a specialist pharmacist supplies Viagra on a pharmacist written prescription or using a 'patient group direction'. In November 2017 Pfizer was granted an application to reclassify sildenafil 50mg as a separate 'P' medicine which is available without prescription and is called Viagra Connect. In all cases only registered pharmacies are permitted to supply it.

Are Viagra, Cialis, and Levitra as strong as each other?

Yes, generally men will respond equally well to the equivalent dose of these tablets. The equivalent strengths of each is as follows:

DrugLow strengthMedium strengthHigh strength
Viagra (sildenafil)25mg50mg100mg
Cialis (tadalafil)5mg10mg20mg
Levitra (vardenafil)5mg10mg20mg

Some men might find they feel a stronger response to one type of treatment rather than another although this is generally not the case. There is also an alternative daily dose of Cialis 2.5mg and 5mg tablets for men who require continuous treatment.

Should I take Viagra on an empty stomach?

Viagra tablets will usually take around 30-45 minutes to take effect when taken on an empty stomach, and up to 60-90 minutes if taken within 30 minutes after a meal. High-fat meals will delay absorption longer than lower-fat ones.

Can Viagra go out of date?

The shelf life of most medicine tablets is 5 years. This means they will stay in-date for 5 years after the manufactured date written on the packet. It should be stored at below 30°C, which means keeping tablets out of direct sunlight. Packets will be printed with expiry dates and you should always read the information leaflet enclosed in packs.

Tablets remain effective after their 'use-by' date expires - see medicine expiry dates - however official advice is they should be taken to a pharmacy for safe disposal.

See also erectile dysfunction FAQs page.

Dr Tony Steele

Authored 7 December 2012 by Dr Tony Steele
MB ChB Sheffield University 1983. Former hospital doctor and GP.

Reviewed by Dr B. Babor, Dr A. Wood, Dr P. Hunt
Last reviewed 19 June 2019
Last updated 30 July 2020


Product reviews

Viagra rated 4.46/5 in 266 product reviews

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not working

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The original and better than generic substitutes

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