Sildenafil Teva
From £3.99
If you are researching Viagra dosage, you have probably noticed that most of what comes up online reads like a fixed formula: start here, move there, follow these steps. In reality, dosing for a prescription-only medicine like sildenafil is an individual clinical decision, made between you and your prescriber, based on your health, your response, and how you tolerate the medicine. This guide explains what the three available strengths are, how they generally differ, and what actually determines the right one for you, without telling you what to take.
Viagra and generic sildenafil are both prescription-only medicines (POMs) in the UK. No article, including this one, can responsibly tell you which strength to use. What it can do is explain the clinical picture clearly enough that your consultation makes sense and you know what to expect.
The Three Available Strengths
| Strength | General clinical positioning | Typically considered for |
|---|---|---|
| 25mg | Lower strength | Men for whom a lower dose may be more appropriate, including some people with severe kidney or liver impairment or certain medicine interactions, based on individual assessment. |
| 50mg | Standard starting point | Most adults beginning treatment without additional risk factors identified at assessment |
| 100mg | Maximum strength | Considered when a lower dose has not provided an adequate response and is well tolerated. |
This table describes how these strengths are generally positioned in clinical practice. It is not a set of instructions, and it does not replace an individual assessment. Your own starting point depends on factors specific to you, including your age, other health conditions, other medicines you take, and how you respond and tolerate treatment over time.
Why the Dose Is Not a Simple Escalation
A common assumption is that everyone starts at 25mg and works up, or that the biggest number is simply the best result. Neither is accurate. UK primary care guidance generally supports starting most adults on the standard strength unless there is a specific reason to start lower, and the maximum strength is not automatically superior for those who already respond well to a lower one.
A higher dose is not automatically better for everyone. While some men may benefit from an increase to 100 mg when 50 mg is insufficient, higher doses can also increase the likelihood of side effects. This is why "the right dose is the lowest one that works for you" is a genuinely accurate clinical principle, not just a reassuring phrase.
What "not working" actually means before any change is considered
UK clinical guidance generally recommends giving a PDE5 inhibitor such as sildenafil several opportunities to work, with adequate stimulation and correct use, before deciding that it has not been effective. Viagra is usually taken about 1 hour before use, and the timing and response can vary between individuals. A single disappointing attempt, particularly a first attempt, does not necessarily mean the dose or medicine itself is wrong. Anxiety around first use, how the medicine is taken, and the amount of stimulation involved can all affect the result. If the response remains inadequate, discuss it with your prescriber rather than changing the dose yourself.
How Sildenafil Works for Erectile Dysfunction, Briefly
Sildenafil is a PDE5 inhibitor. During arousal, the body releases nitric oxide, which relaxes blood vessels in the penis and increases blood flow. An enzyme called PDE5 normally breaks down the chemical signal responsible for that relaxation. Sildenafil blocks PDE5, helping that signal last longer. It does not create arousal by itself, stimulation is still required for it to have any effect, regardless of strength.
This mechanism is identical across all three strengths. What changes with dose is the degree of PDE5 inhibition achieved, not the underlying process.
Generic Sildenafil vs Branded Viagra, at Any Strength
Generic sildenafil and branded Viagra contain the same active ingredient, sildenafil citrate, and are available in the same strengths. Authorised generic medicines must meet relevant UK quality and regulatory requirements and demonstrate bioequivalence to the reference medicine where applicable. Generic sildenafil is therefore expected to provide comparable therapeutic effects to Viagra when used as authorised.
Clinical Evidence on Dose and Effectiveness
Sildenafil's efficacy across doses has been studied extensively since its original approval. A pooled analysis of 11 double-blind, placebo-controlled trials involving 2,667 men found significantly improved erectile function with sildenafil compared with placebo, consistent across a broad range of ages, causes and severity of erectile dysfunction. In clinical trials, 74 percent of men with erectile dysfunction reported improvements using the 50 mg dose. In long-term extension studies following patients for up to a year, the substantial majority of men who continued treatment reported that it had improved their erections and that they were satisfied with the outcome.
A separate trial comparing men who continued on 50 mg with men titrated up to 100 mg after an initial period on 50 mg found that those who moved to the higher dose showed a further, statistically significant improvement in erectile function scores, without an increase in the frequency or severity of side effects. These findings suggest that dose adjustment may provide additional benefit for some men when the initial dose is not sufficient, while supporting the use of an initial trial before considering a higher dose.
Safety Considerations That Apply at Every Strength
The dose does not change the underlying safety profile in kind, only in degree. The following are important safety considerations for sildenafil, regardless of which strength is prescribed.
Medicines that must not be combined with sildenafil
- Nitrate medicines, such as glyceryl trinitrate (GTN) spray and isosorbide, used for angina.
- Nicorandil, a medicine used for angina that also has a nitrate-like action.
- Riociguat, used for certain types of pulmonary hypertension.
- Recreational nitrates, sometimes known as poppers.
Combining any of these with sildenafil, at any strength, can cause a dangerous, sudden drop in blood pressure. This is one of the central checks in any genuine clinical assessment. Sildenafil also has important drug interactions with some alpha-blockers used for prostate disease and with certain other medications that can affect sildenafil levels or blood pressure.
Tell your prescriber about grapefruit or grapefruit juice consumption, as it may affect sildenafil levels.
Only one dose in any 24-hour period
Regardless of strength, only one dose should be taken within any 24-hour period, which reflects the maximum daily dose and recommended maximum dose for use frequency. Taking more than one dose does not improve the result, and taking too much Viagra or more than one tablet in that period meaningfully increases the risk of side effects and overdose-related harm, including a drop in blood pressure. If you have already taken a dose, do not take another dose within the same 24-hour period.
When higher strengths carry more caution
Side effects such as headache, facial flushing and visual disturbances, including a blue-tinged appearance to vision and blurred vision, become somewhat more likely as the dose increases. A higher dosage raises the risk of side effects and does not justify exceeding the maximum recommended dosage of 100 mg. Seek urgent medical attention if you experience a sudden decrease in hearing or serious vision symptoms affecting one or both eyes.
For this reason, an increase to a higher strength should be based on the response to treatment and tolerability rather than assuming that the highest strength is best.
What Actually Determines Your Right Viagra Dosage and Starting Dose
- Your age and general health, including kidney and liver function. Although no routine dose adjustment is required solely because someone is aged 65 or over, a lower dose may be considered depending on individual circumstances.
- Other medicines you are taking, particularly nitrates, alpha-blockers or medicines that affect how sildenafil is broken down, some interactions may require dosage adjustments.
- Ritonavir can substantially increase sildenafil exposure. Co-administration is not advised, if it does occur, the sildenafil dose should not exceed 25 mg within 48 hours.
- Cardiovascular health, including blood pressure and any history of heart problems.
- Whether you have used a PDE5 inhibitor before and how you responded, which can help a prescriber judge the right sildenafil dosage.
- Any side effects you have experienced with similar medicines previously.
None of these can be assessed from a form alone, these are the kinds of changes a doctor determines during prescribing. GPhC guidance for online pharmacy services, updated in February 2025, is explicit that prescribing from a questionnaire without genuine review is not acceptable, and that a prescriber should be able to verify what you have told them and communicate with you directly. A legitimate online prescribing service should allow the prescriber to decline treatment or request further information when clinically appropriate.
How the Consultation and Prescription Process Works
- Complete an online medical questionnaire covering your health history, current medications and cardiovascular health.
- A UK-registered prescriber reviews your answers individually and may ask follow-up questions.
- If sildenafil or Viagra is considered appropriate, a prescribed dosage is selected based on your individual circumstances.
- Your prescription is dispensed by a GPhC-registered pharmacy in properly labelled packaging.
- Your prescriber remains available if the dose needs to be reviewed after you have tried it.
Take the tablet whole with water. Taking sildenafil with food, particularly a high-fat meal, may delay its onset of action.
EverydayMeds currently lists sildenafil from £3.99 and Viagra from £27.99. Prices and available strengths may change, so check the live price and product availability at checkout.
Medical Disclaimer
This article is provided for general information only and does not constitute medical advice. It is not a substitute for consultation with a qualified healthcare professional. Prescription sildenafil and Viagra are prescription-only medicines. The appropriate strength, dosing and timing for any individual depend on a clinical assessment carried out by a qualified prescriber, and this article does not recommend or instruct any specific dose. Do not start, stop, increase or decrease any medicine, including any change between sildenafil strengths, without speaking to your prescriber first. If you experience an erection lasting more than 4 hours, chest pain, sudden vision or hearing changes, or symptoms of a severe allergic reaction, seek urgent medical attention.
