BNF Sildenafil Dosage Strengths & Guidelines

Sildenafil is available in three standard dosage strengths (25mg, 50mg, 100mg) as outlined in the British National Formulary. Understanding the correct dosage for your needs is essential for safe and effective treatment. Our UK-licensed prescribers assess each patient individually to determine the most appropriate starting dose. At EverydayMeds, you can choose between generic sildenafil or branded Viagra during checkout.

  • 25mg - Lower strength for those requiring dose reduction
  • 50mg - Standard starting dose for most patients
  • 100mg - Maximum strength for enhanced effectiveness
  • One tablet maximum per 24-hour period
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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.

Complete Sildenafil Dosage Information

Standard Sildenafil Dosage Strengths

According to BNF guidelines, sildenafil is manufactured in three standardised strengths. The 50mg tablet represents the typical starting dose for most adult men experiencing erectile dysfunction. This strength provides an optimal balance between effectiveness and tolerability for the majority of patients.

25mg Sildenafil - Reduced Strength

The 25mg strength may be recommended for patients who experience side effects with higher doses, those over 65 years of age, or individuals taking certain medications that could interact with sildenafil. This lower dose reduces the risk of adverse effects whilst potentially maintaining therapeutic benefit.

50mg Sildenafil - Standard Starting Dose

Most patients begin treatment with 50mg sildenafil, taken approximately one hour before sexual activity. This dose has been clinically proven effective for the majority of men with erectile dysfunction. Our prescribers typically recommend starting with this strength unless specific factors suggest otherwise.

100mg Sildenafil - Maximum Strength

The 100mg tablet represents the maximum recommended dose. This strength may be prescribed if the 50mg dose proves insufficient, provided the lower strength was well-tolerated. Patients should never exceed 100mg within a 24-hour period, as this significantly increases the risk of serious side effects.

Choosing Between Viagra and Sildenafil

Both branded Viagra and generic sildenafil contain identical active ingredients in the same dosage strengths. The choice between them often comes down to personal preference and cost considerations. At EverydayMeds, we offer both options, allowing you to select your preferred treatment during the checkout process.

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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