Sildenafil Strength Comparison: BNF Dosage Guide

Understanding sildenafil dosages according to BNF guidelines helps you make informed treatment decisions. Available in 25mg, 50mg, and 100mg strengths, sildenafil offers flexible dosing options for erectile dysfunction treatment. Whether you choose generic sildenafil or branded Viagra, the active ingredient and effectiveness remain identical. Our UK-licensed clinicians can help determine the most suitable strength based on your individual needs and medical history during your confidential consultation.

  • 25mg: Starting dose for those sensitive to medications or with certain medical conditions
  • 50mg: Standard recommended starting dose for most men with erectile dysfunction
  • 100mg: Maximum dose, typically prescribed when 50mg proves insufficient
  • Generic sildenafil offers identical effectiveness to Viagra at a more affordable price point
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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.

Comparing Sildenafil Strengths and Treatment Options

BNF Recommended Sildenafil Dosing

The British National Formulary (BNF) provides clear guidance on sildenafil dosing for erectile dysfunction. The standard starting dose is 50mg, taken approximately one hour before sexual activity. This dose may be adjusted based on individual response and tolerability, with options to reduce to 25mg or increase to the maximum 100mg dose. Only one dose should be taken within a 24-hour period, regardless of the strength chosen.

25mg Sildenafil: When Lower Strength is Preferred

The 25mg strength is typically recommended for men who may be more sensitive to medications or have certain health conditions. This includes older patients (over 65), those with liver or kidney impairment, or men taking certain medications that may interact with sildenafil. Despite being the lowest strength, 25mg can still provide effective results for many patients whilst minimising potential side effects such as headaches or facial flushing.

50mg: The Standard Starting Point

Most men begin their erectile dysfunction treatment with 50mg sildenafil, as recommended by BNF guidelines. This strength offers an optimal balance between effectiveness and tolerability for the majority of patients. Clinical studies demonstrate that 50mg provides satisfactory results for approximately 70% of men with erectile dysfunction. If this dose proves effective with minimal side effects, there's typically no need to adjust the strength.

100mg: Maximum Strength for Optimal Results

The 100mg dose represents the maximum recommended strength for sildenafil treatment. This higher dose may be prescribed when 50mg doesn't provide sufficient improvement in erectile function. Whilst more effective for some patients, the 100mg strength may increase the likelihood of side effects. Healthcare providers carefully evaluate whether the potential benefits outweigh any increased risk of adverse reactions before prescribing this maximum dose.

Generic Sildenafil vs Branded Viagra: Value Comparison

Both generic sildenafil and branded Viagra contain identical active ingredients and undergo the same rigorous quality standards. The primary difference lies in cost, with generic sildenafil typically offering significant savings compared to the branded alternative. At EverydayMeds, patients can choose between both options at checkout, allowing you to select based on personal preference and budget considerations whilst receiving the same therapeutic benefits.

Effectiveness Timeline and Duration

Regardless of strength, sildenafil typically begins working within 30-60 minutes of administration. The medication's effects can last up to 4-6 hours, though this doesn't mean an erection persists for this duration. Sexual stimulation remains necessary for the medication to work effectively. Taking sildenafil with a large or fatty meal may delay its onset of action, so timing your dose appropriately can optimise results.

Safety Considerations Across All Strengths

All sildenafil strengths carry similar contraindications and precautions. The medication should never be combined with nitrate medications due to dangerous blood pressure interactions. Men with cardiovascular conditions, recent stroke or heart attack, or severe liver problems require careful medical evaluation before starting treatment. Our comprehensive consultation process ensures sildenafil is suitable and safe for your individual circumstances, regardless of the prescribed strength.

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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