How Long Does Viagra Last and Who Is Eligible?

Viagra typically lasts 4-6 hours in your system, though this doesn't mean you'll have an erection for this duration. The medication helps improve blood flow when you're sexually aroused during this window. Understanding who can safely take Viagra is crucial, as it's not suitable for everyone. At EverydayMeds, we offer both branded Viagra and generic sildenafil following a clinical assessment by UK-licensed prescribers.

  • Viagra effects last 4-6 hours but don't cause continuous erection
  • Adult men over 18 with erectile dysfunction may be eligible
  • Clinical assessment required to check medical history and interactions
  • Not suitable for those taking nitrates or with severe heart conditions
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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.

Duration of Effects and Eligibility Requirements

How Long Do Viagra's Effects Last?

Viagra's effects typically last between 4 to 6 hours after taking the tablet. This timeframe represents how long the medication remains active in your system, not how long an erection will last. The medication works by increasing blood flow to the penis when you become sexually aroused during this period. It's important to understand that Viagra doesn't cause automatic erections - sexual stimulation is still required for the medication to work effectively.

Who Can Take Viagra?

Viagra is prescribed for adult men aged 18 and over who experience erectile dysfunction. To be eligible, you must complete a clinical assessment with a UK-licensed prescriber who will evaluate your medical history, current medications, and overall cardiovascular health. The assessment ensures Viagra is safe and appropriate for your individual circumstances.

At EverydayMeds, patients can choose between branded Viagra and generic sildenafil during checkout. Both contain the same active ingredient (sildenafil citrate) and work identically, with sildenafil offering a more cost-effective option whilst maintaining the same clinical effectiveness.

Medical Conditions That May Affect Eligibility

Certain medical conditions require careful consideration before prescribing Viagra. Men with well-controlled diabetes, mild to moderate high blood pressure, or previous heart problems may still be eligible following thorough assessment. However, those with severe cardiovascular disease, recent heart attacks or strokes (within six months), or severe liver impairment are typically not suitable candidates for this medication.

Contraindications and Safety Considerations

Viagra is absolutely contraindicated for men taking nitrate medications such as GTN sprays or isosorbide tablets, as this combination can cause dangerous drops in blood pressure. Other contraindications include severe heart disease, very low blood pressure, recent stroke or heart attack, and certain rare eye conditions affecting the retina.

The medication is also not recommended for those taking certain other medications that can interact dangerously, including some HIV protease inhibitors and specific antifungal medications. During your consultation, it's crucial to disclose all medications, supplements, and recreational substances you're using.

Starting Treatment and Dosage Considerations

Most men start with a 50mg dose of sildenafil, taken approximately one hour before sexual activity. Depending on effectiveness and any side effects experienced, the dose may be adjusted to 25mg or increased to 100mg. Only one tablet should be taken within any 24-hour period, regardless of the strength prescribed.

The medication should be taken on an empty stomach or after a light meal for optimal effectiveness. Heavy or fatty meals can delay the onset of action, potentially reducing the medication's effectiveness during your intended timeframe.

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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