Sildenafil (Generic Viagra)

Sildenafil (Generic Viagra)

Sildenafil is an erectile dysfunction treatment that works by increasing blood flow to your penis to make it easier to get and stay hard. It starts working within 30-60 minutes of taking it and is effective for around 74% of people.

In stock
from £14.99

Product details

Sildenafil is an affordable treatment for erectile dysfunction, that is effective for 74% of men who try it. Sildenafil starts working within an hour of taking it, and lasts for up to 6 hours.

Sildenafil is the generic version of Viagra, and works in the same way at a lower cost. We also offer Superdrug sildenafil, which is a type of sildenafil that is available over the counter.

Dr Louisa Draper

Medically reviewed by

Dr Louisa Draper

Last reviewed: 24 Jun 2021

Sildenafil prices

Starting prices for the different pack sizes. Available Sildenafil dosages are 25mg, 50mg and 100mg.

Pack Size Price
4 tablets from £15.99
8 tablets from £23.00
12 tablets from £40.50
16 tablets from £44.00
28 tablets from £78.00
40 tablets from £111.00
56 tablets from £152.00

How it Works

About Sildenafil

How to buy sildenafil online

Can I buy sildenafil online?

Yes, you can buy sildenafil safely and legally from trusted online sellers, such as Superdrug Online Doctor. All orders are delivered in discreet packaging, and our doctors can provide free expert advice if you have any questions about sildenafil.

Sildenafil is a prescription-only medication. Online doctor services that can prescribe sildenafil, like Superdrug Online Doctor, are the only safe and legal option if you want to buy sildenafil online. Our doctors assess your health and will only prescribe if it's safe and appropriate for you to take sildenafil. Any online pharmacy which is prepared to sell sildenafil without a prescription is untrustworthy, and could potentially be selling fake or dangerous medication.

If you’re not sure about buying your medication online, make sure the site you’re buying from is properly regulated by organisations like the Care Quality Commission.

Important: When you order a generic (non-branded) medication, it may arrive in different packaging or under a different name to what’s pictured or what you expect. This is because we order from a variety of different suppliers to make sure you always have your medication available when you need it. The medication you receive will contain the same active ingredients and work in exactly the same way.

Can I buy sildenafil over the counter?

Sildenafil is a prescription-only medication, so you cannot buy it over the counter. However, there is an alternative that works in the same way called Viagra Connect that is available over the counter without a prescription.

What are sildenafil tablets?

Sildenafil is a prescription treatment for erectile dysfunction, and is the generic form of Viagra. It is a type of medication known as a PDE-5 inhibitor, which helps you get an erection by increasing blood flow to your penis. It works in the exact same way as Viagra, except it can be manufactured by any pharmaceutical company, which means it is usually available at a lower price.

What strengths of sildenafil are there?

Sildenafil comes in 3 strengths, 50mg, 25mg, and 100mg:

  • 50mg is the dosage most people start on and it works for most men who try it
  • 25mg is the dosage you could try if you’ve already tried 50mg and it worked but you had some mild side effects – 25mg might improve these side effects
  • 100mg is the dosage you could try if you tried 50mg and you didn’t get any side effects but you also didn’t see the results you hoped for – 100mg can work when 50mg doesn’t

Make sure to check with a doctor before switching the dosage of any medication If you’ve never used sildenafil before and you’re not sure which dose to try, we recommend 50mg.

Because they’re the same medication, sildenafil and Viagra have the same dosages. See our page on Viagra (Sildenafil) Dosages for more information.

How does sildenafil work?

Sildenafil works the same way as Viagra. It improves the blood flow to your penis, making it easier for you to get an erection that’s hard enough for sex if you’re sexually aroused. How to take sildenafil:

You should take sildenafil about an hour before you want to have sex. This gives your body time to absorb the medication, so it can start working. Swallow one tablet of sildenafil whole with water. For the best results when taking sildenafil, you should avoid eating heavy or fatty meals beforehand. These types of food can slow down how quickly your body can absorb sildenafil after you take it, which can make it take longer to start working.

Drinking alcohol can make sildenafil less effective and can also make the side effects of sildenafil worse. While alcohol is often used by some people to overcome nerves and sexual anxiety, it can actually make it more difficult to get an erection.

How often can I take sildenafil?

You can safely take sildenafil every day, as long as it is prescribed by your doctor. However, you may want to try longer lasting erectile dysfunction medications like Cialis Daily, which are designed to help you have more spontaneous sex without having to take a pill just before sex.

You should only take one sildenafil tablet per day, even if it’s a 25mg tablet (the lowest dose available). If you take more sildenafil that your doctor has prescribed, then it may be unsafe as you have not been assessed for that dosage, and the drug levels may build up in your body, causing side-effects, so you should not take multiple doses in any 24 hour period. 100mg is the maximum amount of sildenafil you can take in one day.

How long does sildenafil last?

Sildenafil lasts for 4-6 hours after you take a tablet. This means that you’ll be able to get an erection while you are aroused during this time, and not that you’ll have an erection that lasts for 6 hours.

See our How Long Does Viagra (Sildenafil) Last page for more information.

Does sildenafil make you last longer?

If you find it difficult to keep an erection, sildenafil can help you to get and maintain an erection, so you can stay hard for longer. However, sildenafil won’t help if you are orgasming too quickly. For more information, you can read our doctors’ advice on how to last longer, and if sildenafil can help.

Reviews of sildenafil

Sildenafil is an effective treatment, but it doesn’t work for everyone:

What’s the difference between sildenafil and Viagra?

Sildenafil is the generic version of Viagra, which means that any pharmaceutical company can make and sell it. Viagra is a branded medication that can only be made by Pfizer. Sildenafil and Viagra work in exactly the same way, the only difference is the branding on the box and tablets. Sildenafil is usually cheaper than Viagra, as you’re not paying for the brand name.

If you’re not sure which to choose, remember they both have the same active ingredient and both are safe as long as a doctor approves treatment for you. We don’t recommend one over the other.

See our page on the differences between Viagra Connect, Viagra, and Sildenafil for more information.

Sildenafil vs tadalafil

If you need help choosing:

  • Both are about as effective as each other – even though sildenafil has higher dosage numbers, that doesn’t mean it’s stronger overall
  • If you want a longer-lasting medication, you might want to choose tadalafil or Tadalafil Daily
  • If you don’t want to have to plan to take your medication before sex, you might want to choose Tadalafil Daily

Since sildenafil and tadalafil are the active ingredients in Viagra and Cialis, you can see our Viagra vs Cialis vs Levitra page for more information.

Sildenafil vs Viagra

Sildenafil vs Viagra Sildenafil Viagra
Effective for... 74% of users 74% of users
Our Trustpilot rating 4.6 out of 5 4.6 out of 5 rating 8.2 8.5
Can you buy it online? Yes Yes
Over the counter version Viagra Connect Viagra Connect
Available on the NHS? Yes Only for some people
Available dosages  25mg, 50mg, 100mg 25mg, 50mg, 100mg
How fast do they work? 30 to 60 mins 30 to 60 mins
How long do they last?  4 to 6 hours 4 to 6 hours

Sildenafil vs tadalafil

Sildenafil vs Tadalafil Sildenafil Tadalafil
Effective for... 74% of users 60-70% of users
Our Trustpilot rating 4.6 out of 5 4.3 out of 5 rating 8.2 8.5
Over the counter version Viagra Connect No
Daily dosage? No Yes
Available dosages 25mg, 50mg, 100mg 2.5mg, 5mg, 10mg, 20mg
How fast do they work? 30 to 60 mins 30 mins*
How long do they last? 4 to 6 hours Up to 36 hours*

* these time apply to 10mg or 20mg doses you take before sex – the 2.5mg and 5mg daily doses are always working

Sildenafil safety information

Sildenafil can cause some side effects and it may react with other medication you’re taking. For full safety information, please read the patient information leaflet that comes with your medication.

Side effects of sildenafil

Less than 2% of people appear to get side effects when taking sildenafil. If you do get side effects they are likely to be mild. If you think you’re having sildenafil side effects, talk to your doctor. See our Viagra (Sildenafil) Side Effects page for more information.

Common side effects:

  • headache
  • nausea
  • indigestion
  • blocked nose
  • facial flushing
  • hot flushes
  • eyes problems, such as blurred vision
  • dizziness

Uncommon side effects:

  • vomiting
  • skin rash
  • eyes irritation/pain
  • bloodshot eyes
  • seeing flashes of light
  • visual brightness
  • sensitivity to light
  • rapid heartbeat
  • muscle pain
  • feeling sleepy or tired
  • blocked sinuses
  • upper abdominal pain
  • feeling hot
  • nosebleeds
  • arm or leg pain
  • blood in urine
  • watery eyes
  • Rare side effects:
  • irregular heartbeat
  • heart attack
  • stroke
  • fainting
  • numb mouth
  • temporary reduced blood flow to brain
  • tightening in the throat
  • double vision
  • swelling of the eye or eyelid
  • abnormal sensations in the eye
  • spots in your vision
  • dilated pupils
  • discolouring of the whites of the eyes
  • bleeding from the penis
  • blood in semen
  • dry nose
  • irritability
  • swelling on the inside of the nose
  • sudden loss of hearing

Serious side effects:

If you experience the following, you should stop taking sildenafil and seek medical help immediately:

  • allergic reaction – symptoms include breathing difficulties, dizziness, swelling of face, lips, or tongue
  • chest pains

Drug interactions

The following drugs can interact with sildenafil. You should make sure you tell your doctor if you are taking any of the following:

  • nitrates
  • nitric oxide donors (“poppers”)
  • protease inhibitors (used to treat HIV)
  • alpha-blocker therapy
  • riociguat used for pulmonary hypertension

Herbal or complementary remedies could also interfere with sildenafil and potentially cause side effects. If you are taking any herbal remedies, you should speak to your doctor to make sure there isn’t a risk of interaction.

Pre-existing conditions

Sildenafil is not suitable for some men who have certain medical conditions. For example, you may not be suitable for sildenafil treatment if you have:

  • a serious heart or liver problem
  • take nitrates for a chest pain
  • recently had a stroke or a heart attack
  • low blood pressure
  • a rare inherited eye disease
  • You should also let your doctor know if you have:
  • sickle cell anaemia
  • Peyronie’s disease or a penis deformity
  • a heart problem
  • a stomach ulcer
  • a bleeding problem like haemophilia

Sildenafil FAQs

What is it like before and after sildenafil?

Before taking sildenafil, you may have trouble getting or keeping an erection. After taking sildenafil, you should find that it starts working in 30 to 60 minutes, and the effects last for around 4 hours. Sildenafil causes the blood vessels in your penis to relax and improves blood flow, which should help you to get and keep an erection more easily. For more information, read our page on what to expect before and after starting sildenafil.

What if sildenafil doesn’t work?

Sildenafil is effective for most men, but it doesn’t work for everyone. It is worth trying sildenafil on a few separate occasions to see if it will work for you. If you are taking 25mg or 50mg of sildenafil and you’re still finding it difficult to get or maintain an erection, then you may want to ask a doctor about trying sildenafil 100mg. If you try sildenafil 100mg and it does not work for you, then sildenafil may not be the right erectile dysfunction treatment for you, and you may want to try other options.

It is also important that you have an assessment by your doctor to try and find out the cause of your erectile dysfunction. This ensures there is nothing serious wrong, and they may even be able to find a cause that they can treat.

Are there any alternatives to sildenafil?

There are several alternatives to sildenafil. Similar medicines include tadalafil, vardenafil and avanafil, which are prescription medications that work in similar ways. Some men find that lifestyle changes, such as exercise or stopping smoking, can also be helpful in overcoming erectile dysfunction, as well as discussing with a doctor to address any psychological cause like anxiety. For more helpful information on what other options are available to treat erectile dysfunction, read our doctors recommendations on Sildenafil alternatives.

Can women take sildenafil?

No, women can’t take sildenafil. It is only licensed for men in the UK, though in places such as the USA there is “female sildenafil” or “female Viagra” available. These drugs work in a completely different way to sildenafil for men, and are used to increase sexual desire and satisfaction in women, though there is limited evidence that they actually work. For more information on how sildenafil affects women, read our doctors’ advice about what happens when women take sildenafil.

Can I take sildenafil with other erectile dysfunction medications?

No, you should never take sildenafil with another erectile dysfunction medication. Erectile dysfunction medications all work in the same way, so taking them together could cause serious side effects, or even cause an overdose.

Does sildenafil expire?

Sildenafil, like most medications, has a shelf life and can become less effective if it’s left unused for too long. You should check the expiry date on your packet, and make sure you take it before then. Sildenafil should be stored below 30°C and out of direct sunlight.

If your sildenafil is past the expiration date, it might not be safe to take it. In this case, take the box to the pharmacy to be safely disposed of and buy a new packet of sildenafil.

Why do I need to get a prescription?

Sildenafil is a prescription-only medication, which means that a doctor has to make sure it’s safe for you to take it. This is because it may react with other medications you are taking, or may not be suitable for you if you have certain health conditions.

What causes erectile dysfunction?

There are many different factors that can cause erectile dysfunction, and often there are several factors working together, not just a single cause. This can include psychological factors such as stress, to physical problems with your circulation. For more information, read our doctors’ advice on the causes of erectile dysfunction.


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Medicines Information. (2019) NHS [Accessed 02nd September 2020]

Sildenafil Dosage. (2018) [Accessed 02nd September 2020]

Sildenafil Effectiveness. (1999) Drugs [Accessed 02nd September 2020]

Sildenafil Interactions. (2020) NICE [Accessed 02nd September 2020]

Sildenafil Patient Leaflet. (2019) Accord [Accessed 02nd September 2020]

Sildenafil. (2019) NHS [Accessed 02nd September]

Patient Reviews