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Start your free online consultation to find out whether sildenafil is the right erectile dysfunction treatment for you.

What is sildenafil?

Sildenafil is medicine, taken in the form of a tablet, which can be used to treat symptoms of erectile dysfunction (ED) in men over the age of 18. Sildenafil is also sold under the brand name Viagra Connect.

Sildenafil works by helping to relax the blood vessels in your penis[1], allowing blood to flow into your penis when you get sexually aroused. Sildenafil will only help you to get an erection if you are sexually stimulated.

If you have a low libido, understanding the cause of this and getting help to increase your libido may change the way you think and feel about sex. This may then help improve your erection problems. 

Talk to your doctor if you have low libido. There is support available that may help, including talking to a professional such as a psychologist or counsellor. Your doctor may be able to refer you for counselling, or you can refer yourself through the NHS.

Find out which of our ED treatments is suitable for you, online and for free.

How does sildenafil work?

Sildenafil works by helping to relax the blood vessels in your penis[1], this allows blood to flow into your penis as you become sexually aroused. It's important to note that sildenafil will only help you to get an erection if you are sexually stimulated.

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If you have erectile dysfunction (ED), difficulty getting or keeping an erection, there is treatment and support available that can help, including medicines such as sildenafil. Start your consultation to find out which of our ED treatments is suitable for you.

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How should I take sildenafil?

If you’ve decided to take sildenafil tablets to treat your erection problems you should swallow one whole tablet with some water up to four hours before you want to have sex[1]. It's important that you don’t take more than one tablet a day[1]. 

If you're not sure how to take sildenafil talk to your GP or a pharmacist. They’ll be able to give you more information and support.

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How long does it take for sildenafil to work?

It usually takes 30 to 60 minutes for sildenafil to work[1]. It's advised that you take one tablet about an hour before they want to have sex. But everyone is different and for some people, it may take more or less time to get an erection after taking sildenafil. 

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How long does sildenafil last?

Once you've taken sildenafil, it will stay active for up to four hours [3]. It is important to remember that you will only experience an erection once you become sexually aroused.

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What are the common side effects of sildenafil?

You may experience some side effects from taking sildenafil. Side effects[1],[2] can include:

  • headaches

  • sickness (nausea)

  • feeling dizzy

  • hot flushes

  • blurred vision.

Talk to your GP or a pharmacist if you experience any side effects after taking sildenafil. Find out more about all the possible side effects on the NHS website.

If sildenafil isn’t suitable for you, there are other treatment options available that may help. These include:

  • vacuum pump

  • injections

  • pellets 

  • cream. 

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Is there a difference between sildenafil and Viagra?

The main differences between the two medications are that Viagra is a brand-name medication produced by Pfizer. Whereas sildenafil is the active ingredient found in Viagra that is responsible for its positive function. Another difference is that sildenafil is available to purchase over the counter whereas Viagra needs to be prescribed to you by your GP [3,4].

More information about sildenafil

Here are some of our frequently asked questions about sildenafil

Where can I get further support and information?

As well as talking to your GP for information and support, there are also a number of organisations and charities offering support and information.


  1. 1.

    Sildenafil (Viagra): medicine for erection problems. Published August 29, 2018. Accessed January 25, 2021.
  2. 2.

    Sildenafil 50mg film-coated tablets - Summary of Product Characteristics (SmPC) - (emc). Accessed January 26, 2021.
  3. 3.

    Sildenafil 50 mg film-coated tablets - Patient Information Leaflet (PIL) - (emc). Accessed September 29, 2021.
  4. 4.

    Viagra 100 mg film-coated tablets - Summary of Product Characteristics (SmPC) - (emc). Accessed September 4, 2020.