How Does Viagra Work? Quick Reference Guide

Viagra is the brand name for sildenafil citrate, a prescription medication used to treat erectile dysfunction in men. It works by increasing blood flow to the penis when sexually aroused, helping achieve and maintain an erection. The medication typically takes effect within 30-60 minutes and can remain effective for 4-6 hours. EverydayMeds offers both branded Viagra and generic sildenafil following an online consultation.

  • Blocks PDE5 enzyme to increase blood flow to the penis
  • Works within 30-60 minutes when sexually stimulated
  • Effects may last 4-6 hours (not continuous erection)
  • Available in 25mg, 50mg, and 100mg strengths
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Not sure which one? Here's the honest comparison.

Sildenafil
~60 min
~4 hrs
you like to plan ahead
Tadalafil (as-needed)Most prescribed
~30 min
up to 36 hrs
you want a whole weekend covered
Tadalafil Daily
always active
continuous
you never want to think about timing
Vardenafil
~15–30 min
~8 hrs
you want the fastest onset

How ED treatment works in your body.

Increases blood flow

Increases blood flow

When PDE5 is suppressed, blood is able to flow more freely through the body—including to the (you guessed it) penis.

Increase erections

Increase erections

More blood flow to the penis means harder, more satisfying erections once you're sexually stimulated.

Understanding Viagra's Mechanism of Action

How Viagra Functions in the Body

Viagra contains the active ingredient sildenafil citrate, which belongs to a class of medicines called PDE5 inhibitors. When a man becomes sexually aroused, the body naturally releases nitric oxide in the penis, which helps relax blood vessels and increase blood flow. However, an enzyme called phosphodiesterase type 5 (PDE5) can break down this process too quickly, preventing sufficient blood flow for an erection.

Viagra works by temporarily blocking the PDE5 enzyme, allowing the blood vessels in the penis to remain relaxed for longer periods. This enhanced blood flow helps men with erectile dysfunction achieve and maintain an erection suitable for sexual activity. It's important to understand that Viagra does not cause automatic erections - sexual stimulation is still required for the medication to be effective.

Timing and Duration of Effects

Most men find that Viagra begins working within 30 to 60 minutes of taking the tablet. However, this timing can be affected by various factors, including food consumption. Taking Viagra with a large or high-fat meal may delay its onset of action, so many healthcare providers recommend taking it on an empty stomach or after a light meal for optimal results.

The effects of Viagra can last for approximately 4 to 6 hours, though this doesn't mean an erection will persist for this entire duration. Rather, it means the medication remains active in your system, potentially making it easier to achieve erections during this timeframe when sexually aroused. After this period, the medication is gradually eliminated from the body.

Dosage Options and Personalisation

Viagra is available in three strengths: 25mg, 50mg, and 100mg tablets. Healthcare providers typically start patients on a 50mg dose, which can then be adjusted based on effectiveness and any side effects experienced. Some men may find that 25mg is sufficient for their needs, whilst others may require the 100mg strength for optimal results.

It's crucial to take only one dose within a 24-hour period, regardless of the strength prescribed. The medication should be taken approximately 30-60 minutes before planned sexual activity. At EverydayMeds, patients can choose between branded Viagra or generic sildenafil during checkout - both contain the same active ingredient and work identically, with sildenafil offering a more cost-effective alternative.

Safety Considerations and Consultation Process

Before prescribing Viagra, healthcare providers must assess whether it's safe for each individual patient. This involves reviewing cardiovascular health, current medications, and medical history. Viagra is not suitable for men taking nitrate medications (such as GTN spray) due to potentially dangerous interactions that can cause severe drops in blood pressure.

At EverydayMeds, all patients undergo a comprehensive online consultation with UK-licensed prescribers who evaluate eligibility and determine the most appropriate treatment plan. This ensures that Viagra is prescribed safely and effectively for each individual's specific circumstances.

What you need to know about erectile dysfunction

It's one of the most common conditions we treat, and one of the most treatable.

What is Erectile Dysfunction?
ED means finding it hard to get or keep an erection firm enough for sex. It's not unusual to have an off night; the point at which it's worth doing something is when it's happening regularly, or when it's starting to bother you.
How will I feel when I take ED medication?
For most men, nothing feels different day to day. The medication works in the background — when you're sexually aroused, it helps blood flow where it's needed, so erections come more easily and last longer. It doesn't cause arousal on its own. Some men notice mild, short-lived effects like a headache, facial flushing or a stuffy nose, which usually pass as the dose wears off.
Why do I need a prescription for ED medication?
ED treatments are prescription-only medicines in the UK because they aren't suitable for everyone — for example, alongside certain heart conditions or medications like nitrates. That's why we ask you to complete a short online consultation first. A UK-registered prescriber reviews your answers to make sure your chosen treatment is safe and right for you before it's dispensed.
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