Sildenafil dosages: A complete guide
- Available strengths and the standard starting dose: What MHRA and NHS guidance recommends for most men
- When to adjust your dose
- Answers to common dosage questions, such as whether 100 mg is safe, why 200 mg is not, and whether daily use is advisable
- How and when to take sildenafil
- Dosage guidance for men over 65, and those with kidney or liver conditions
- What to do if the prescribed dose does not work
- Available sildenafil strengths
- The standard starting dose: 50 mg
- When to adjust the dose
- Is it safe to take 100 mg of sildenafil?
- Can I take 200 mg of sildenafil?
- How much sildenafil is too much?
- Is it safe to take sildenafil every day?
- How and when to take sildenafil
- Dosage adjustments for specific groups
- What to do if a dose does not work
- Final thoughts
Available sildenafil strengths
Sildenafil is available in three dose strengths in the UK, all requiring a prescription, with the exception of Viagra Connect 50 mg, which is available from pharmacies following a suitability assessment.
| Strength | Typical use | Maximum frequency |
|---|---|---|
| 25 mg | Lower starting dose for men over 65 or those sensitive to sildenafil | Once in 24 hours |
| 50 mg | Standard starting dose for most men | Once in 24 hours |
| 100 mg | Where 50 mg is insufficiently effective, under prescriber guidance | Once in 24 hours |
No dose above 100 mg is licensed or recommended. The maximum dose is 100 mg once per day.
The standard starting dose: 50 mg
The standard recommended starting dose for most men with erectile dysfunction is 50 mg, taken approximately one hour before sexual activity. This is the dose recommended in the MHRA Summary of Product Characteristics and reflected in NHS prescribing guidance.
The 50 mg dose strikes the right balance for most men between effectiveness and tolerability. Starting here allows you and your prescriber to assess how well it works and whether any side effects are noticeable, before considering any adjustment.
Good to know
Sildenafil does not need to be taken every day. It is an on-demand medicine, taken when needed rather than on a fixed daily schedule. This distinguishes it from daily tadalafil, which is a separate prescribing approach discussed later in this article.
When to adjust the dose
The right dose of sildenafil is the lowest one that works effectively for you with minimal side effects. If 50 mg is not producing the desired result, or if it is working but causing problematic side effects, a prescriber can adjust the dose in either direction. Here is when each adjustment is typically considered.
Going up to 100 mg
If 50 mg is not producing a sufficient effect after several attempts under reasonable conditions, for example, taken on an empty stomach, with adequate time before sexual activity, in the absence of excessive alcohol, your prescriber may recommend increasing the dose to 100 mg. This is the maximum licensed dose.
Increasing to 100 mg should always be done under prescriber guidance, not as a self-adjustment. A higher dose increases the likelihood of side effects including headache, flushing, dizziness, and visual disturbances, and may not be appropriate for all men.
Important!
Do not increase your dose to 100 mg without speaking to your prescriber first. If 50 mg has not worked, a prescriber can assess whether a higher dose is appropriate, or whether a different medicine such as tadalafil may be a better fit.
Going down to 25 mg
A lower dose of 25 mg may be recommended for men who find 50 mg effective but experience side effects that affect their experience or wellbeing. A reduction in dose often reduces side effect severity without significantly compromising effectiveness for men who respond well to sildenafil.
25 mg is also commonly the recommended starting dose for men over 65, and for those with kidney or liver conditions that affect how the body processes the medicine.
Is it safe to take 100 mg of sildenafil?
For most healthy men under prescriber guidance, yes. 100 mg is a licensed dose within the approved range and is used safely by many men for whom 50 mg is insufficient.
However, 100 mg is not appropriate for everyone. It carries a higher risk of side effects than lower doses, and certain groups should not take it without careful prescriber assessment, including men over 65, those with cardiovascular conditions, those with kidney or liver impairment, and those taking other medicines that interact with sildenafil.
Important!
100 mg is the maximum licensed dose. It should only be taken on the advice of a prescriber, not as a first attempt or a self-escalation when a lower dose has not immediately produced the desired effect.
Can I take 200 mg of sildenafil?
No. 200 mg exceeds the maximum recommended dose and is not licensed or clinically supported.
Clinical studies found that taking more than 100 mg increased the frequency and severity of side effects, including a higher rate of visual disturbances, without producing any improvement in effectiveness. Taking 200 mg does not produce a stronger or longer-lasting effect than 100 mg. What it does do is significantly increase the risk of serious side effects including severe headache, dangerous drops in blood pressure, vision disturbances, and in rare cases, cardiovascular events.
If 100 mg is not working, the answer is not a higher dose. It is a conversation with your prescriber about whether sildenafil is the right medicine for you, or whether an alternative such as tadalafil may be more effective.
Important!
Never take more than 100 mg of sildenafil in a 24-hour period. If you have accidentally taken more than the recommended dose, contact NHS 111 or seek medical advice promptly.
How much sildenafil is too much?
The maximum recommended dose is 100 mg once per 24 hours. Taking more than this at any one time, or taking multiple doses within 24 hours, constitutes an overdose.
Symptoms of sildenafil overdose can include severe headache, significant dizziness or fainting, vision disturbances, chest pain, nausea, and in serious cases a dangerous drop in blood pressure. If you or someone else has taken more than the recommended dose and is experiencing concerning symptoms, call 999 or go to your nearest A&E.
Is it safe to take sildenafil every day?
Standard on-demand sildenafil (25 mg, 50 mg, or 100 mg) is not recommended for daily use. It is designed to be taken when needed, up to a maximum of once per day, rather than as a daily preventative treatment.
This is an important distinction from daily tadalafil. Tadalafil has a separate licensed daily dosing regimen at low doses (2.5 mg or 5 mg), specifically designed for continuous use. This option is suitable for men who have sex frequently or who prefer not to plan around taking a tablet. Sildenafil does not have an equivalent licensed daily dosing schedule.
If you are considering a daily approach to ED treatment, discuss the daily tadalafil option with your prescriber.
Good to know
Some men take sildenafil several times a week without issue, within the one-per-24-hours limit. There is no clinical evidence that regular use at recommended doses causes harm, but daily use as a routine is not the intended or licensed approach for standard sildenafil.
How and when to take sildenafil
Sildenafil is taken orally, swallowed whole with a glass of water. The key practical considerations are timing and food.
Timing
Take sildenafil approximately one hour before sexual activity. This allows enough time for the tablet to be absorbed and reach effective blood levels. Some men find it effective in as little as 30 minutes; others may need closer to 90 minutes, particularly after food.
Food
Taking sildenafil after a large, high-fat meal delays absorption and can reduce peak blood levels, making it less effective or slower to act. For the most reliable onset, take it on an empty stomach or after a light, low-fat meal.
Alcohol
Modest alcohol consumption is unlikely to prevent sildenafil from working, but alcohol lowers blood pressure and can worsen side effects including dizziness and flushing. Heavy drinking before taking sildenafil is not advisable and can contribute independently to erectile difficulties.
Good to know
Sildenafil can be taken at any time of day. There is no requirement to take it at a specific time, only to allow sufficient time between taking it and sexual activity.
Dosage adjustments for specific groups
For most healthy adult men, the standard 50 mg starting dose applies. However, certain health conditions and age-related changes affect how the body processes sildenafil, and a lower starting dose is recommended in some circumstances.
Men over 65
The body clears sildenafil more slowly with age, meaning blood levels remain higher for longer in some men over 65. For this reason, a starting dose of 25 mg is often recommended for men over 65, with an increase to 50 mg only if the lower dose is well tolerated but insufficiently effective. The 100 mg dose should only be considered in men over 65 after careful prescriber assessment.
Men with kidney impairment
Mild to moderate kidney impairment does not typically require dose adjustment. In men with severe kidney impairment, sildenafil clearance is reduced and a starting dose of 25 mg is recommended. Your prescriber will advise based on your kidney function results.
Men with liver impairment
The liver is responsible for metabolising sildenafil. In men with mild to moderate hepatic impairment, a starting dose of 25 mg is recommended and the maximum dose may be lower than for the general population. Sildenafil is contraindicated in severe liver impairment.
What to do if a dose does not work
If sildenafil does not produce the desired effect on a given occasion, do not take a second dose. Taking two doses within 24 hours is not safe and does not improve efficacy.
Before concluding that sildenafil is not working, consider the following:
- Was there sufficient time between taking the tablet and attempting sexual activity? Allow at least one hour, and up to 90 minutes if taken after food.
- Was the tablet taken after a large, high-fat meal? This significantly delays and reduces absorption.
- Was alcohol consumed beforehand? Heavy drinking can both delay onset and contribute to ED independently.
- Was there sufficient sexual stimulation? Sildenafil requires arousal to work and will not produce an erection in the absence of it.
If sildenafil consistently fails to produce an effect after several attempts under reasonable conditions, speak to your prescriber. A dose increase, a switch to tadalafil, or a review of underlying factors may all be appropriate next steps.
Final thoughts
Sildenafil dosing is straightforward for most men, but getting it right makes a real difference to both effectiveness and tolerability. Starting at 50 mg, allowing adequate time before sexual activity, and taking it away from heavy meals covers the basics for the majority of people.
If the standard approach is not working as expected, the right response is always a conversation with your prescriber, not a self-escalation above the licensed dose. A brief consultation can identify whether a dose adjustment, a change in timing, or an alternative medicine is the more appropriate next step.
FAQ
How much sildenafil should I take the first time?
For most men, the recommended starting dose is 50 mg, taken approximately one hour before sexual activity. If you are over 65 or have kidney or liver conditions, your prescriber may recommend starting at 25 mg.
Can I take sildenafil with food?
Yes, but food affects how quickly it works. A large, high-fat meal significantly delays absorption and can reduce effectiveness. For the most predictable onset, take sildenafil on an empty stomach or after a light meal.
What is the maximum dose of sildenafil?
The maximum licensed dose is 100 mg, taken no more than once in any 24-hour period. Doses above 100 mg are not licensed, do not improve efficacy, and significantly increase the risk of side effects.
Can I take 200 mg of sildenafil?
No. 200 mg exceeds the maximum recommended dose and is not clinically supported. It does not produce a stronger effect and increases the risk of serious adverse events. If 100 mg is not effective, speak to your prescriber rather than increasing the dose further.
Is it safe to take sildenafil every day?
Standard on-demand sildenafil is not designed or licensed for daily use. If you would benefit from a daily approach, daily low-dose tadalafil is a licensed alternative worth discussing with your prescriber.
What should I do if sildenafil is not working?
Do not take a second dose. Review the practical factors above, and if the medicine consistently fails to produce an effect after several attempts in good conditions, speak to your prescriber about a dose review or alternative treatment.
The DoktorABC medical advisory board
Dr. Roland Ruiken
Medical advisor, Norway
Dr. Viktor Simunovic
Medical advisor, Croatia
