For erectile dysfunction, the usual recommended sildenafil dose is 50mg taken when needed approximately one hour before sexual activity. Depending on response and tolerability, a prescriber may reduce the dose to 25mg or increase it to 100mg. Sildenafil should not normally be taken more than once a day, and sexual stimulation is required for it to work.
People searching for sildenafil BNF information are often looking for a clear summary of licensed doses, prescribing checks, interactions and patient advice. The British National Formulary is a professional medicines reference. This article provides a patient-friendly explanation based on current official UK sources; it does not reproduce the BNF and should not be used as a substitute for the current BNF monograph, the product information or individual prescribing advice.
If you are considering treatment, you can review generic sildenafil tablets available after an online clinical consultation. For a deeper practical comparison of 25mg, 50mg and 100mg, use the Sildenafil dosage guide.
What does the BNF say about sildenafil?
The BNF provides healthcare professionals with practical information on medicine indications, doses, contraindications, cautions, interactions, side effects and prescribing considerations. For sildenafil, it distinguishes between its uses, because erectile dysfunction and pulmonary hypertension have different dosing schedules.
For erectile dysfunction in adults, the licensed product information describes 50mg as the usual recommended dose taken when needed approximately one hour before sexual activity. The dose may be adjusted to 25mg or 100mg according to effectiveness and tolerability. The maximum recommended dose is 100mg, and the maximum recommended dosing frequency is once per day.
The BNF is not a self-prescribing tool. A dose that appears in a medicine reference still needs to be interpreted in the context of the person’s health, other medicines, previous response and risk factors. The prescription label and prescriber’s instructions take priority for the individual patient.
Sildenafil BNF information at a glance
| Prescribing question | Patient-friendly summary | Important qualification |
|---|---|---|
| Licensed ED indication | Treatment of erectile dysfunction in adult men. | Sexual stimulation is required for sildenafil to support an erection. |
| Usual recommended dose | 50mg when needed. | The right starting dose is individual and may differ. |
| Dose range for ED | 25mg, 50mg or 100mg. | Dose changes should follow prescriber advice. |
| When to take it | Approximately one hour before sexual activity. | It may be taken up to four hours beforehand, but individual onset varies. |
| Maximum dose | 100mg. | Doses above 100mg are not recommended and do not improve efficacy. |
| Maximum frequency | Once per day. | Do not take a second dose because the first seems slow or ineffective. |
| Food | Can be taken with or without food. | A heavy meal can delay the onset of action. |
| Sexual stimulation | Required. | Sildenafil does not increase libido or cause an automatic erection. |
| Under 18s | Not indicated for erectile dysfunction. | Different indications and specialist regimens must not be confused with ED treatment. |
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What is sildenafil and how does it work?
Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor used to treat erectile dysfunction. During sexual stimulation, natural chemical signals relax blood vessels in the penis and increase blood flow. Sildenafil reduces the action of the PDE5 enzyme, helping this blood-flow response last long enough to achieve and maintain an erection.
The medicine does not create sexual desire and does not cause a continuous or automatic erection. Sexual arousal is still necessary. If an erection problem is persistent, the underlying cause may also need assessment because erectile dysfunction can be associated with cardiovascular risk factors, diabetes, medicine effects, stress, anxiety and other health conditions.
For a broader overview of causes and available options, review Medicina’s erectile dysfunction treatments.
Sildenafil 25mg, 50mg and 100mg doses
The three standard tablet strengths used for erectile dysfunction are 25mg, 50mg and 100mg. They contain the same active medicine and work through the same mechanism. The difference is the amount of sildenafil in each tablet, not a different type of treatment.
| Strength | Typical prescribing role | When it may be considered | Important point |
|---|---|---|---|
| 25mg | Reduced dose. | May be considered where a lower starting dose is appropriate, including some people with severe kidney or liver impairment, certain medicine interactions or alpha-blocker use. | It is not automatically the best first dose for every new user. |
| 50mg | Usual recommended starting dose for many adults. | Often used to assess response and tolerability when no factor indicates a lower dose. | It can be reduced or increased after clinical review. |
| 100mg | Maximum recommended dose. | May be considered when 50mg has not provided an adequate response, has been used correctly and the higher dose is suitable. | It should not be selected simply because it is the strongest tablet. |
Read the individual guides for Sildenafil 25mg, Sildenafil 50mg and Sildenafil 100mg when you need strength-specific information. The detailed Sildenafil dosage guide explains dose selection and adjustment in more depth.
How does a prescriber choose the sildenafil dose?
Dose selection is not based only on how severe erectile dysfunction feels. A prescriber considers the likely benefit, the risk of side effects and factors that can increase sildenafil exposure or blood-pressure effects.
- Previous response to sildenafil or another PDE5 inhibitor.
- Whether side effects occurred at a previous dose.
- Kidney and liver function.
- Current medicines, including alpha-blockers and medicines that inhibit CYP3A4.
- Cardiovascular health and whether sexual activity is medically advisable.
- Blood pressure and a history of dizziness or postural hypotension.
- The accuracy of timing, food intake and sexual stimulation during previous attempts.
A higher dose may increase exposure and the likelihood or intensity of side effects. It should not be assumed that 100mg is more appropriate because erectile dysfunction is distressing or because 50mg did not work on one occasion. The prescriber may first review whether the medicine was taken correctly and whether another factor affected the response.
How to take sildenafil correctly
- Take the prescribed dose approximately one hour before anticipated sexual activity unless your prescriber has given different instructions.
- Swallow the tablet with water.
- Do not take more than one dose in a day.
- Allow time for the medicine to work and remember that sexual stimulation is required.
- Be aware that a heavy meal can delay the onset.
- Avoid excessive alcohol because it can make erections more difficult and may increase dizziness or other unwanted effects.
- Do not combine sildenafil with another ED medicine unless a prescriber has specifically instructed you to do so.
Do not take an extra tablet because the first dose has not worked immediately. Sildenafil commonly starts working within about 30 to 60 minutes, but timing varies between individuals. The effect window is not the same as a continuous erection; the medicine supports the erectile response when sexual stimulation occurs.
The planned guide on how long sildenafil lasts will explain onset, duration and factors that influence the treatment window in more detail.
What if sildenafil 50mg does not work?
One unsuccessful attempt does not automatically mean the dose is too low. Before a dose is changed, it is useful to review how the medicine was taken. Common reasons for a poor response include taking it immediately after a heavy meal, not allowing enough time, waiting too long, drinking excessive alcohol, insufficient sexual stimulation or an underlying physical or psychological factor.
Do not increase from 50mg to 100mg without clinical advice. The higher strength may be considered only when the current dose has been used correctly, the response remains inadequate and the prescriber considers an increase appropriate. If side effects occur, a lower dose or another treatment may be more suitable.
Read Why sildenafil may not work for a practical review of timing, meals, alcohol, stimulation, health conditions and treatment expectations.
Who should not take sildenafil?
Sildenafil is not suitable for everyone. It must not be used with nitrate medicines or nitric oxide donors because the combination can cause a dangerous fall in blood pressure. It is also contraindicated with riociguat.
The licensed product information also lists important situations in which sildenafil is contraindicated or requires careful assessment. These include severe cardiovascular conditions where sexual activity is inadvisable, very low blood pressure, severe liver impairment, a recent heart attack or stroke, certain inherited retinal disorders and previous vision loss caused by non-arteritic anterior ischaemic optic neuropathy (NAION).
A consultation is needed because the relevant risk cannot be judged from age or symptoms alone. Provide complete and accurate information about your health and every medicine, supplement or recreational substance you use.
For a fuller suitability guide, read Sildenafil safety information.
Sildenafil interactions and prescribing cautions
Some interactions are absolute contraindications, while others may require a lower starting dose, closer assessment or avoidance. Do not stop a regular medicine to make sildenafil use possible. The prescriber must assess the combination.
| Medicine or substance | Why it matters | What to do |
|---|---|---|
| Nitrates for angina or nitric oxide donors such as amyl nitrite (“poppers”) | Can cause a dangerous fall in blood pressure when combined with sildenafil. | Do not use with sildenafil. Disclose all prescribed and recreational nitrate use. |
| Riociguat | Can increase the risk of symptomatic low blood pressure. | Do not use with sildenafil. |
| Alpha-blockers | The combined blood-pressure-lowering effect may cause dizziness or postural hypotension. | The person should be stable on alpha-blocker treatment; a 25mg sildenafil starting dose may be considered. |
| CYP3A4 inhibitors, including some antifungals, antibiotics and HIV treatments | Can increase sildenafil exposure. | The prescriber may consider a lower dose or avoid the combination. |
| Ritonavir | Can markedly increase sildenafil exposure. | Co-administration is not advised in the licensed product information. |
| Other ED medicines or other sildenafil-containing products | Can increase exposure and adverse effects. | Do not combine unless specifically directed by a prescriber. |
| Herbal remedies and supplements | Safety and interaction evidence may be limited. | List every product during the consultation; do not assume “natural” means safe. |
If you develop chest pain during or after sexual activity, seek medical help and tell the healthcare professional when sildenafil was taken. Do not use nitrate medicine to treat the chest pain after taking sildenafil.
Sildenafil side effects and urgent warning signs
Like all medicines, sildenafil can cause side effects, although not everyone gets them. Headache is very common. Other common effects include nausea, flushing, indigestion, temporary visual changes, a blocked nose and dizziness. These effects are often mild to moderate and short-lived, but persistent or troublesome symptoms should be discussed with a healthcare professional.
Stop taking sildenafil and seek urgent medical help for serious symptoms such as:
- Chest pain during or after sexual activity.
- A severe allergic reaction with breathing difficulty or swelling.
- An erection that is painful or lasts more than four hours.
- A sudden decrease or loss of vision.
- A seizure or another severe, rapidly worsening reaction.
A higher dose can increase the likelihood or severity of unwanted effects. Do not use the side-effect list alone to decide whether a medicine is suitable; contraindications and interactions also need assessment.
Kidney, liver and age-related dose considerations
Age alone does not automatically require a lower sildenafil dose. The licensed information states that routine dose adjustment is not required solely because a person is aged 65 or over. However, older adults may be more likely to have health conditions or take medicines that affect suitability, so individual assessment remains important.
For mild to moderate kidney impairment, the usual adult dosing recommendations may apply. In severe kidney impairment, sildenafil clearance is reduced and a 25mg dose may be considered. A reduced starting dose may also be considered in liver impairment because clearance is reduced.
The presence of kidney or liver disease does not mean a person should choose 25mg independently. Severity, other medicines, cardiovascular status and the overall risk-benefit assessment determine whether sildenafil is appropriate and which dose should be used.
Sildenafil for erectile dysfunction versus pulmonary hypertension
Sildenafil is used for both erectile dysfunction and pulmonary hypertension, but the doses and schedules are different. This is a common source of confusion when people search BNF information.
| Indication | Typical medicine pattern | Key safety message |
|---|---|---|
| Erectile dysfunction | 25mg, 50mg or 100mg taken when needed, with 50mg the usual recommended dose for many adults and a maximum frequency of once per day. | Use only the ED dose prescribed for you; sexual stimulation is required. |
| Pulmonary hypertension | A separate regular dosing regimen, commonly 20mg three times daily in adults, under specialist or prescriber guidance. | Do not apply pulmonary-hypertension instructions to ED treatment or vice versa. |
Different strengths, formulations and prescribing pathways may be used for pulmonary hypertension. If sildenafil has been prescribed for that condition, follow the specialist or prescriber’s instructions rather than information written for erectile dysfunction.
Is the BNF a patient information leaflet?
No. The BNF is primarily a professional medicines reference. The patient information leaflet supplied with a specific sildenafil product is written for patients and contains product-specific instructions, contraindications, warnings, side effects and storage information.
Read the leaflet supplied with your tablets before use and keep it for reference. Different licensed products can have different appearances and inactive ingredients, so use the leaflet for the product actually supplied. Ask a pharmacist or prescriber if any instruction is unclear.
The BNF, Summary of Product Characteristics and patient leaflet serve different purposes. None replaces an individual consultation, because a safe prescribing decision depends on information that a general reference cannot know about you.
Should you use BNF information to choose your own sildenafil dose?
No. BNF dose information describes recognised prescribing parameters; it does not establish that a particular dose is suitable for a specific person. Do not choose 100mg because it is the maximum dose, split tablets without advice, combine strengths, or take extra tablets after an inadequate response.
The goal is the lowest suitable dose that provides an adequate response with acceptable side effects. That decision may change over time if health conditions, medicines, response or tolerability change.
Persistent erectile dysfunction should also be assessed rather than managed only by repeated dose escalation. It can sometimes be associated with cardiovascular risk factors, diabetes, hormone problems, mental health factors or medicine effects.
How to arrange sildenafil treatment online
Medicina uses a consultation-led process for prescription sildenafil treatment. The medical questionnaire helps the prescriber assess erectile dysfunction symptoms, cardiovascular health, blood pressure, current medicines, contraindications, previous treatment response and the most appropriate strength.
- Review the Sildenafil treatment page and the available strengths.
- Complete the online medical questionnaire accurately.
- A UK-registered prescriber reviews the information.
- If treatment is clinically appropriate, the pharmacy dispenses the prescribed medicine and supplies the relevant instructions and patient information.
- Follow the prescription label and seek advice if the treatment is ineffective, too strong or causes troublesome effects.
You can view Sildenafil treatment and start an online consultation. Completing the questionnaire does not guarantee that a prescription will be issued.
Conclusion
The key sildenafil BNF dose information for erectile dysfunction is that 50mg is the usual recommended dose for many adults, taken when needed approximately one hour before sexual activity. A prescriber may reduce the dose to 25mg or increase it to 100mg according to response, tolerability, health conditions and medicine interactions. The maximum recommended dose is 100mg and sildenafil should not normally be taken more than once a day.
BNF information should support professional prescribing, not self-selection of a dose. Follow the prescription label, read the patient information leaflet, disclose all medicines and health conditions, and do not combine sildenafil with nitrates, riociguat or another ED treatment unless specifically instructed by a prescriber.
For treatment access, use a regulated consultation so a prescriber can determine whether sildenafil is suitable and which strength is appropriate.
FAQs
What is the BNF dose of sildenafil for erectile dysfunction?
For many adults with erectile dysfunction, the usual recommended sildenafil dose is 50mg taken when needed approximately one hour before sexual activity. Depending on response and tolerability, a prescriber may reduce the dose to 25mg or increase it to 100mg. The maximum recommended dosing frequency is once per day.
Is sildenafil 50mg the usual starting dose?
Yes. Sildenafil 50mg is the usual recommended starting dose for many adults with erectile dysfunction. It is not automatically the right dose for everyone, so medical history, other medicines, kidney or liver function, response and side effects must be considered.
When may sildenafil 25mg be considered?
A 25mg dose may be considered when a reduced starting dose is appropriate, including in some people with severe kidney or liver impairment, people taking certain interacting medicines, or people using alpha-blockers. The prescriber decides whether this applies to the individual.
Is sildenafil 100mg the maximum dose for erectile dysfunction?
Yes. Sildenafil 100mg is the maximum recommended dose for erectile dysfunction. It may be considered when 50mg has not provided an adequate response and the higher dose is clinically appropriate. Do not increase the dose yourself.
How often can sildenafil be taken?
Sildenafil for erectile dysfunction should not normally be taken more than once in a day. Follow the prescription label and do not take an extra dose because the first tablet appears slow to work or has not produced the expected response.
Does food affect how sildenafil works?
Sildenafil can be taken with or without food, but a heavy meal can delay how quickly it starts working. Sexual stimulation is still required, and the medicine does not cause an automatic erection.
Can sildenafil be taken with nitrate medicines?
No. Sildenafil must not be taken with nitrate medicines or nitric oxide donors because the combination can cause a dangerous fall in blood pressure. It is also contraindicated with riociguat. Always provide a complete medicine list during assessment.
Can kidney or liver problems change the sildenafil dose?
Yes. Sildenafil clearance can be reduced in severe kidney impairment and in liver impairment, so a 25mg dose may be considered. The appropriate dose and whether treatment is suitable must be decided by a prescriber.
Does sildenafil work without sexual stimulation?
No. Sildenafil supports the natural erectile response by improving blood flow during sexual stimulation. It does not increase sexual desire and does not create an automatic erection.
Is the sildenafil dose for erectile dysfunction the same as the dose for pulmonary hypertension?
No. Sildenafil is used for more than one condition, and the dose and schedule are different. Erectile dysfunction treatment commonly uses 25mg, 50mg or 100mg when needed, while pulmonary hypertension uses a separate regular dosing regimen under specialist or prescriber guidance. Do not interchange the instructions.
Disclaimer
This page provides general information and is not a substitute for the current BNF, the Summary of Product Characteristics, the patient information leaflet or personal medical advice. Sildenafil is not suitable for everyone and can interact with other medicines. Always follow the prescription label and the instructions supplied by your prescriber and pharmacist. Seek urgent medical help for chest pain, a severe allergic reaction, sudden vision loss or an erection lasting more than four hours.
