How Does Viagra Work? Complete Guide

Viagra works by increasing blood flow to the penis when sexually stimulated. This prescription medication contains sildenafil citrate, a PDE5 inhibitor that blocks specific enzymes affecting blood circulation. Understanding how Viagra functions helps ensure safe, effective use. EverydayMeds offers both branded Viagra and generic sildenafil options following clinical assessment by UK-licensed prescribers.

  • Blocks PDE5 enzyme to improve blood flow to the penis
  • Requires sexual arousal to work effectively
  • Takes 30-60 minutes to start working
  • Effects can last 4-6 hours but erection doesn't persist
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Not sure which one? Here's the honest comparison.

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

Viagra Mechanism of Action and Clinical Guidelines

How Viagra Works in the Body

Viagra contains sildenafil citrate, which belongs to a class of medications called PDE5 inhibitors. When sexually aroused, the body naturally produces nitric oxide, which increases levels of cGMP - a chemical that relaxes blood vessels in the penis. Viagra works by blocking the PDE5 enzyme that normally breaks down cGMP, allowing blood vessels to remain dilated and improving blood flow to erectile tissue.

Timing and Effectiveness

Viagra typically begins working within 30-60 minutes of taking the tablet. The medication requires sexual stimulation to be effective - it doesn't cause automatic erections. Effects can last 4-6 hours, though this doesn't mean an erection will persist for this duration. Food, particularly fatty meals, may delay the onset of action. For optimal results, take Viagra on an empty stomach or after a light meal.

Available Doses and Usage Guidelines

Viagra is available in 25mg, 50mg, and 100mg strengths. The typical starting dose is 50mg, which can be adjusted based on effectiveness and tolerability. Only one dose should be taken within a 24-hour period. EverydayMeds offers both branded Viagra and generic sildenafil - both contain the same active ingredient, with sildenafil providing a more cost-effective option.

Safety Considerations and Contraindications

Before starting Viagra, patients must undergo clinical assessment with a UK-licensed prescriber. The medication is contraindicated for men taking nitrate medications (such as GTN spray), those with severe heart conditions, or recent stroke/heart attack history. Blood pressure medications, particularly alpha-blockers, may interact with Viagra and require dose adjustments. Always disclose all current medications during consultation.

Getting Viagra Through EverydayMeds

EverydayMeds provides convenient access to both Viagra and sildenafil following online consultation with qualified prescribers. Our clinical assessment ensures the medication is suitable for your individual health profile. Patients can choose between branded Viagra or generic sildenafil at checkout, both offering the same therapeutic benefits with discreet UK delivery.

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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