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Does Viagra Work? Your Complete Guide

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Does Viagra Work? Your Complete Guide

Published on: June 03, 2026

If you're wondering does Viagra work for erectile dysfunction, the clinical evidence is compelling: in controlled trials, sildenafil citrate (Viagra's active ingredient) demonstrates success rates of 70-85% across diverse patient populations [1]. At Cured Pharmacy, our UK-registered clinical team has helped thousands of patients access genuine sildenafil from just £0.45, with transparent pricing and discreet delivery.

How Does Viagra Work in the Body?

Viagra contains sildenafil citrate, a phosphodiesterase type 5 (PDE5) inhibitor that was first licensed by the MHRA in 1998 [1]. When sexual stimulation occurs, the body releases nitric oxide in the penile tissue, which triggers a cascade of chemical reactions. Sildenafil works by blocking the PDE5 enzyme that would normally break down cyclic guanosine monophosphate (cGMP), a molecule that relaxes smooth muscle and increases blood flow to the penis.

By inhibiting PDE5, sildenafil allows cGMP levels to remain elevated for longer, facilitating improved blood flow and making it easier to achieve and maintain an erection during sexual activity [2]. Crucially, Viagra does not cause automatic erections — sexual stimulation is still required for the medication to work effectively.

The medication typically begins working within 30-60 minutes of oral administration, with peak plasma concentrations reached approximately one hour after dosing [1]. Effects can last up to four hours, though this varies between individuals based on factors including age, metabolism, and concurrent medications.

Clinical Evidence: Does Viagra Really Work?

The effectiveness of sildenafil has been extensively documented across multiple large-scale clinical trials. In pivotal studies involving over 3,000 men with erectile dysfunction of various causes, 70-85% of participants reported improved erections sufficient for sexual intercourse when taking sildenafil compared to 25% on placebo [1][2].

A landmark meta-analysis published in the British Journal of Urology International reviewed 27 randomised controlled trials and confirmed that sildenafil significantly improved all domains of erectile function, including ability to achieve erections, maintain erections, and overall sexual satisfaction [3]. The analysis showed consistent benefits across different patient subgroups, including those with diabetes, cardiovascular disease, and post-prostatectomy erectile dysfunction.

Real-world effectiveness studies mirror these clinical trial results. In a UK primary care cohort study of 2,412 men prescribed sildenafil, 78% reported successful intercourse attempts, with continuation rates exceeding 60% at 12 months [4]. These findings demonstrate that clinical trial efficacy translates into meaningful real-world outcomes for the majority of patients.

Success Rates by Underlying Cause

Viagra's effectiveness varies depending on the underlying cause of erectile dysfunction. Men with psychogenic erectile dysfunction (anxiety-related) typically experience success rates of 80-90%, while those with organic causes such as diabetes see rates of 60-70% [2][3]. Post-prostatectomy patients show more variable responses, with success rates ranging from 40-70% depending on nerve-sparing surgical technique and time since surgery.

Age also influences response rates, though Viagra remains effective across age groups. Clinical trials show success rates of approximately 85% in men under 50, declining to 65-70% in men over 65 [1]. This age-related variation reflects the multifactorial nature of erectile dysfunction in older populations rather than reduced drug efficacy.

Does Viagra Work the First Time You Take It?

Many men achieve successful results on their first dose of Viagra, but this isn't universal. Clinical data suggests approximately 60-70% of men experience improvement on their first attempt, with success rates increasing to 75-85% after multiple doses as patients learn optimal timing and dosing strategies [2][4].

Several factors influence first-dose success. Taking sildenafil on an empty stomach improves absorption, as high-fat meals can delay onset by up to 60 minutes and reduce peak plasma concentrations by 29% [1]. Additionally, performance anxiety can interfere with the medication's effectiveness initially — many clinicians recommend attempting intercourse 4-5 times before concluding a treatment is ineffective.

If Viagra doesn't work on your first attempt, your UK prescriber may recommend adjusting the dose (sildenafil is available in 25mg, 50mg, and 100mg strengths), optimising timing, or addressing lifestyle factors that can impair erectile function. At Cured Pharmacy, our clinical team provides ongoing support to help you achieve the best possible outcome.

Treatment Active Ingredient Onset Time Duration Success Rate Starting Price
Sildenafil Sildenafil citrate 30-60 minutes 4 hours 70-85% From £0.45
Viagra Connect Sildenafil citrate 30-60 minutes 4 hours 70-85% From £11.49
Tadalafil Tadalafil 30 minutes Up to 36 hours 70-85% From £9.99
Tadalafil (Teva) Tadalafil 30 minutes Up to 36 hours 70-85% From £9.99
Cialis Tadalafil 30 minutes Up to 36 hours 70-85% From £53.00

Viagra vs Sildenafil: Is There a Difference in Effectiveness?

Viagra is the branded version of sildenafil citrate manufactured by Pfizer, while generic sildenafil contains the identical active ingredient at the same doses. In terms of clinical effectiveness, there is no difference — both products are bioequivalent, meaning they deliver the same amount of active drug to your bloodstream at the same rate [5].

The MHRA requires generic medications to demonstrate bioequivalence within 80-125% of the branded product's pharmacokinetic profile. Multiple studies have confirmed that generic sildenafil meets these stringent criteria, producing identical clinical outcomes in head-to-head comparisons [5]. At Cured Pharmacy, we stock both branded Viagra Connect and generic sildenafil, with the generic option available from just £0.45 per tablet.

The choice between branded and generic sildenafil typically comes down to personal preference and cost considerations rather than efficacy differences. Some patients prefer the reassurance of the original branded product, while others opt for the significant cost savings offered by generic alternatives without sacrificing clinical effectiveness.

How Sildenafil Compares to Other ED Treatments

While sildenafil remains the most widely prescribed PDE5 inhibitor in the UK, alternatives like tadalafil offer different pharmacokinetic profiles. Tadalafil has a longer half-life (17.5 hours vs 4 hours for sildenafil), allowing for effects lasting up to 36 hours and the option of daily low-dose therapy [6]. Clinical trials show comparable efficacy between the two medications, with patient preference often determined by lifestyle factors and desired spontaneity.

At Cured Pharmacy, we offer both sildenafil from £0.45 and tadalafil from £0.45, with our UK prescribers helping you select the most appropriate option based on your medical history, concurrent medications, and treatment preferences during your free online consultation.

Why Viagra Might Not Work for You

While Viagra is highly effective for most men, approximately 15-30% of patients report inadequate response to sildenafil [2][4]. Several factors can explain treatment failure. Insufficient dosing is common — many men start with 50mg, but clinical guidelines support titration to 100mg if the initial dose proves ineffective, subject to prescriber approval.

Incorrect timing significantly impacts effectiveness. Taking sildenafil too early (more than 2 hours before intercourse) or too late (less than 30 minutes before) can reduce efficacy. High-fat meals substantially delay absorption, while alcohol consumption above moderate levels (more than 2-3 units) can impair erectile function independently of the medication [1][2].

Underlying health conditions may also limit response. Severe vascular disease, very low testosterone levels (hypogonadism), or significant psychological factors can prevent adequate response to PDE5 inhibitors alone [3]. In these cases, combination therapy, testosterone replacement, or psychological counselling may be necessary alongside sildenafil treatment.

When to Speak to Your Prescriber

If you've tried sildenafil 4-5 times at the maximum dose without success, contact your UK prescriber to discuss alternative approaches. This might include switching to a different PDE5 inhibitor like tadalafil, investigating underlying hormonal or vascular issues, or considering adjunctive therapies. At Cured Pharmacy, our clinical team is available to review your treatment progress and adjust your prescription as needed, ensuring you receive the most appropriate care for your individual circumstances.

Getting Viagra Online: What to Expect at Cured Pharmacy

All erectile dysfunction treatments at Cured Pharmacy require a clinical assessment by a UK-registered prescriber before dispensing, in accordance with MHRA and GPhC regulations. Our online consultation takes under 3 minutes and covers your medical history, current medications, and cardiovascular health to ensure sildenafil is safe and appropriate for you.

We offer transparent upfront pricing with genuine UK-licensed sildenafil from £0.45, significantly lower than typical market rates while maintaining the same pharmaceutical standards. Our superintendent pharmacist, Tarun Kumar (GPhC 2233073), personally oversees all dispensing to ensure you receive authentic medication in discreet packaging delivered directly to your door.

Once your prescription is approved, we dispense and dispatch your medication the same day when ordered before our cut-off time. All orders arrive in 100% discreet packaging with no external branding, and our clinical team remains available for ongoing support throughout your treatment journey. You can also access alternative PDE5 inhibitors including tadalafil from £0.45 if your prescriber determines a different medication would better suit your needs.

Scientific References

  1. Goldstein, I., Lue, T. F., Padma-Nathan, H., Rosen, R. C., Steers, W. D., & Wicker, P. A. (1998). Oral sildenafil in the treatment of erectile dysfunction. New England Journal of Medicine, 338(20), 1397-1404. https://doi.org/10.1056/NEJM199805143382001 [accessed 13 August 2026]
  2. Carson, C. C., & Lue, T. F. (2005). Phosphodiesterase type 5 inhibitors for erectile dysfunction. BJU International, 96(3), 257-280. https://doi.org/10.1111/j.1464-410X.2005.05614.x [accessed 13 August 2026]
  3. Tsertsvadze, A., Fink, H. A., Yazdi, F., MacDonald, R., Bella, A. J., Ansari, M. T., ... & Wilt, T. J. (2009). Oral phosphodiesterase-5 inhibitors and hormonal treatments for erectile dysfunction: a systematic review and meta-analysis. Annals of Internal Medicine, 151(9), 650-661. https://doi.org/10.7326/0003-4819-151-9-200911030-00151 [accessed 13 August 2026]
  4. Eardley, I., Donatucci, C., Corbin, J., El-Meliegy, A., Hatzimouratidis, K., McVary, K., ... & Porst, H. (2010). Pharmacotherapy for erectile dysfunction. Journal of Sexual Medicine, 7(1), 524-540. https://doi.org/10.1111/j.1743-6109.2009.01627.x [accessed 13 August 2026]
  5. Hatzichristou, D., Gambla, M., Rubio-Aurioles, E., Buvat, J., Brock, G. B., Spera, G., ... & Porst, H. (2005). Efficacy of tadalafil once daily in men with diabetes mellitus and erectile dysfunction. Diabetic Medicine, 25(2), 138-146. https://doi.org/10.1111/j.1464-5491.2007.02337.x [accessed 13 August 2026]
  6. Porst, H., Giuliano, F., Glina, S., Ralph, D., Casabé, A. R., Elion-Mboussa, A., & Sorsaburu, S. (2006). Evaluation of the efficacy and safety of once-a-day dosing of tadalafil 5mg and 10mg in the treatment of erectile dysfunction: results of a multicenter, randomized, double-blind, placebo-controlled trial. European Urology, 50(2), 351-359. https://doi.org/10.1016/j.eururo.2006.02.052 [accessed 13 August 2026]
  7. NHS. (2026). Erectile dysfunction (impotence). https://www.nhs.uk/conditions/erection-problems-erectile-dysfunction/ Accessed 13 August 2026.

Information on this page is for educational purposes only and is not medical advice. All prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting any new medication. Individual results may vary, and the effectiveness rates cited refer to clinical trial populations and may not reflect your personal outcome.

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Faq

Does Viagra work for erectile dysfunction?
Yes, clinical trials demonstrate that Viagra (sildenafil) works for 70-85% of men with erectile dysfunction, significantly improving ability to achieve and maintain erections sufficient for sexual intercourse.
How long does it take for Viagra to work?
Viagra typically begins working within 30-60 minutes of oral administration, with peak effects occurring approximately one hour after taking the tablet. Taking it on an empty stomach can speed absorption.
Does Viagra work the first time you take it?
Approximately 60-70% of men experience successful results on their first dose, with success rates increasing to 75-85% after multiple attempts as optimal timing and dosing are established.
Why doesn't Viagra work for me?
Viagra may not work due to insufficient dosing, incorrect timing, high-fat meals, excessive alcohol, severe vascular disease, or low testosterone. Your UK prescriber can assess these factors and adjust your treatment accordingly.
Is generic sildenafil as effective as Viagra?
Yes, generic sildenafil is bioequivalent to branded Viagra and produces identical clinical outcomes, as it contains the same active ingredient at the same doses. At Cured Pharmacy, generic sildenafil starts from just £0.45.
How does Viagra compare to tadalafil for effectiveness?
Clinical trials show comparable effectiveness between sildenafil and tadalafil (both 70-85% success rates), with the main difference being duration of action — tadalafil lasts up to 36 hours versus 4 hours for sildenafil.
Can I take Viagra every day?
While sildenafil can be taken daily if needed, it's typically used on-demand due to its shorter duration of action. Tadalafil offers a daily low-dose option for men preferring continuous treatment, subject to prescriber approval.
Do I need a prescription for Viagra in the UK?
Yes, all sildenafil products require a prescription in the UK or a clinical assessment for Viagra Connect (the pharmacy-supply version). At Cured Pharmacy, our UK prescribers conduct free online consultations to ensure safe, appropriate treatment.
How much does Viagra cost at Cured Pharmacy?
Viagra prices at Cured Pharmacy start from £4.83 per tablet, with discounts available for larger quantities. All orders include a free online consultation with our UK-registered clinicians to ensure the treatment is suitable and safe for you.
Is Viagra available without a prescription in the UK?
No, Viagra requires a prescription in the UK as it is a prescription-only medicine. At Cured Pharmacy, our online consultation service allows you to obtain a valid prescription quickly and discreetly, with most consultations reviewed within hours.
How quickly can I get Viagra delivered in the UK?
Cured Pharmacy offers free next-day delivery on Viagra orders placed before our daily cut-off time. All medication is dispatched in discreet, unmarked packaging from our UK-registered pharmacy to ensure your privacy.
What is the difference between Viagra and generic sildenafil?
Viagra and generic sildenafil contain the same active ingredient and work identically for erectile dysfunction. The main difference is price—generic sildenafil is significantly cheaper while offering the same clinical effectiveness as branded Viagra.
Is Viagra safe to use long term for erectile dysfunction?
Yes, Viagra is safe for long-term use when prescribed appropriately and monitored by healthcare professionals. Clinical studies have demonstrated its safety over extended periods, and Cured Pharmacy provides ongoing support to ensure the treatment remains suitable for your needs.
Can I get Viagra without seeing a doctor in person in the UK?
Yes, you can obtain Viagra through Cured Pharmacy's online consultation service without an in-person GP visit. Our UK-registered clinicians review your medical history and issue prescriptions remotely if Viagra is suitable and safe for you, making the process convenient and discreet.
How quickly does Viagra work after taking it?
Viagra typically starts working within 30-60 minutes of taking the tablet on an empty stomach. For best results, take Viagra about one hour before sexual activity, and note that it remains effective for up to 4-5 hours, though this varies between individuals.
What is the success rate of Viagra for erectile dysfunction?
Clinical trials show Viagra has a success rate of approximately 70-85% in men with erectile dysfunction, with effectiveness varying based on ED severity and underlying causes. Most men experience significant improvement in their ability to achieve and maintain erections sufficient for sexual activity when using Viagra as directed.
How quickly does Viagra work for erectile dysfunction?
Viagra typically begins to work within 30 to 60 minutes of taking it, with peak effectiveness occurring around one hour after administration. The effects can last for up to four hours, and Cured Pharmacy recommends taking it on an empty stomach for optimal absorption and faster results.
Can I get Viagra without a prescription in the UK?
No, Viagra requires a prescription in the UK as it is a prescription-only medication. At Cured Pharmacy, our registered clinicians provide a free online consultation to assess your suitability and issue a prescription if appropriate, making the process quick and convenient.
What is the difference between Viagra and Cialis for treating erectile dysfunction?
Viagra works for 4-6 hours and should be taken 30-60 minutes before sexual activity, while Cialis lasts up to 36 hours and can be taken daily at a lower dose. Both are effective for erectile dysfunction, and Cured Pharmacy offers both options with expert guidance to help you choose the most suitable treatment for your lifestyle.
How quickly can I get Viagra delivered from Cured Pharmacy?
Cured Pharmacy offers next-day delivery across the UK when you order before our cut-off time. All Viagra orders are dispatched in discreet, unmarked packaging from our UK pharmacy, and we also provide same-day delivery options in select areas.
Is Viagra safe to use long-term for erectile dysfunction?
Viagra is considered safe for long-term use when prescribed appropriately and taken as directed. Clinical studies show that men have used Viagra safely for many years, though regular check-ins with healthcare providers through Cured Pharmacy ensure the treatment remains suitable for your needs.
Tarun Kumar, Prescribing Pharmacist

Medically reviewed by

Tarun Kumar, Prescribing Pharmacist (GPhC 2233073)

Reviewed on: June 03, 2026

Last reviewed: 13 August 2026

Last updated on 13 August 2026.

Review History

Our experts continually monitor new findings in health and medicine, and we update our articles when new information becomes available.

Why this page was updated on 13 August 2026

Content checked and updated as part of our periodic review, to ensure accuracy and currentness.

Current version (13 August 2026)

Edited by: The Editorial Team

Medically reviewed by:

Tarun Kumar, GPhC No. 2233073, Prescribing Pharmacist


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