Viagra dosage: A complete guide for UK patients

DoktorABC editorial team

Accurate, up-to-date health information written by our editorial team and reviewed by UK-registered prescribers.

What doses is Viagra available in?

Viagra is available in three doses: 25 mg, 50 mg, and 100 mg. All three are prescription-only in the UK, with the exception of Viagra Connect (sildenafil 50 mg), which is available without a prescription from UK pharmacies following a pharmacist consultation. See our guide on Viagra prices based on dose here. 

What is the standard Viagra starting dose?

The recommended starting dose for most men is 50 mg, taken approximately 30-60 minutes before sexual activity. This is consistent with both MHRA prescribing information and NHS guidance on sildenafil.

If 50 mg produces adequate results without significant side effects, there is no clinical reason to increase the dose. If results are insufficient, a prescriber may recommend increasing to 100 mg. If side effects are pronounced at 50 mg, reducing to 25 mg is a reasonable step to discuss with your prescriber.

What is the correct Viagra dosage for a 70-year-old man?

Older men are typically advised to start at the lower 25 mg dose rather than the standard 50 mg.

Age affects how the body processes sildenafil. In men over 65, reduced kidney and liver function means the drug is cleared more slowly, leading to higher blood concentrations from the same dose. This increases the risk of side effects, particularly low blood pressure and dizziness. This is reflected in the Viagra Summary of Product Characteristics at medicines.org.uk, which notes that plasma concentrations of sildenafil are approximately 40% higher in elderly users (aged 65 and over) compared to younger adults, and recommends a starting dose of 25 mg for this group. The NHS also advises caution with sildenafil in older patients.

Does Viagra dosage depend on body weight?

Body weight is not a primary factor in Viagra dosing, unlike some other medications where dose is calculated directly per kilogram. However, it is not entirely irrelevant.

Men with lower body weight may experience stronger effects from the same dose due to higher relative blood concentrations. Conversely, some larger men may find the standard 50 mg dose produces less pronounced effects. That said, the licensed dose range of 25 mg to 100 mg accommodates most individual variation, and dose adjustments based on weight alone are not standard practice.

If you feel the standard dose is either too strong or insufficient, discuss this with your prescriber rather than adjusting independently.

Can you take Viagra every day?

Standard Viagra (25 mg, 50 mg, or 100 mg) is not recommended for daily use. It is designed as an on-demand medication, taken when needed rather than on a fixed daily schedule.

Taking Viagra daily at standard doses increases cumulative exposure to the drug and is not supported by the licensed prescribing guidance. Men who want the convenience of a continuous daily treatment should discuss daily tadalafil (2.5 mg or 5 mg) with their prescriber. Tadalafil has a licensed daily dose specifically designed for this purpose, maintaining a low-level continuous effect without the need to time a dose.

Can I take 50 mg Viagra twice a day?

No. The maximum recommended dose of sildenafil is one dose per 24-hour period, regardless of strength. Taking two doses of 50 mg within 24 hours is equivalent to 100 mg and exceeds the pattern of use for which the drug is licensed. It also increases the risk of side effects including severe hypotension, prolonged erection (priapism), and cardiovascular complications.

If a single 50 mg dose is not producing sufficient results, the appropriate step is to discuss increasing to a single 100 mg dose with your prescriber, not to take multiple doses.

How many Viagra can you take in a day?

One dose per 24-hour period is the maximum. The highest single licensed dose is 100 mg. This applies regardless of the dose strength you are taking.

Can I take 200 mg of Viagra in one day?

No. 200 mg significantly exceeds the maximum licensed dose of 100 mg and carries serious safety risks.

Taking 200 mg of sildenafil in 24 hours substantially increases the risk of severe hypotension (dangerously low blood pressure), priapism (a prolonged erection lasting more than four hours that requires urgent medical treatment), visual disturbances, and cardiovascular complications.

Are there benefits to taking Viagra daily?

Standard Viagra is not licensed or recommended for daily use, and there is no clinical evidence supporting a benefit from taking it daily at standard doses. The concept of daily ED medication is specifically addressed by tadalafil, which has a licensed 2.5 mg and 5 mg daily dose formulation designed for continuous use.

For men who find on-demand dosing inconvenient or who have sex frequently, daily tadalafil is the clinically appropriate option to discuss with a prescriber. It maintains a continuous background effect without the need to time a dose.

When should you take Viagra?

Viagra should be taken approximately 30-60 minutes before sexual activity. This allows sufficient time for the medication to be absorbed and reach effective blood concentrations.

What is the best time of day to take Viagra?

There is no strong clinical evidence that time of day affects Viagra's efficacy. The medication works the same way whether taken in the morning or evening. What matters most is timing it approximately 30-60 minutes before sexual activity and avoiding high-fat food beforehand.

How much Viagra should I take the first time?

Start with the dose your prescriber has recommended, which for most men is 50 mg. Do not start at 100 mg on your first use.

Beginning at 50 mg allows you to assess how your body responds to sildenafil before considering any dose adjustment. Side effects of Viagra are more likely and more pronounced at higher doses, and starting lower gives you a clearer baseline for what to expect.

What should you expect when taking Viagra for the first time?

For most men, the experience of taking Viagra for the first time is straightforward. Within 30-60 minutes of taking the tablet, you may notice:

• Improved response to sexual stimulation
• A mild headache or facial flushing (the most commonly reported effects)
• Slight nasal congestion
• A sense of warmth or mild dizziness

How does Viagra work?

Viagra does not produce an erection independently. Sexual stimulation is required for the medication to produce its effect. If you are expecting an automatic response without arousal, this is a common misconception worth setting aside before your first use.

If side effects are pronounced or uncomfortable, note what you experienced and discuss with your prescriber at your next contact. Do not increase the dose based on a single experience.

What should you do if Viagra is not working?

If Viagra is not producing adequate results, consider the following before concluding it has failed:

• Check timing: Was it taken 30-60 minutes before activity on a relatively empty stomach?
• Check stimulation: Was sufficient sexual arousal present?
• Check alcohol intake: Viagra taken with alcohol reduces both efficacy and arousal
• Consider dose: If you are on 50 mg and have tried it several times without result, discuss increasing to 100 mg with your prescriber

If 100 mg is not producing results, this warrants a clinical review rather than further dose escalation. Underlying vascular, hormonal, or psychological factors may be contributing, and a prescriber can assess whether an alternative treatment or further investigation is appropriate.

DoktorABC connects UK patients with licensed prescribers who can review your dosing history and advise on the most appropriate next step.

Final thoughts

Viagra dosing is straightforward for most men: start at 50 mg, take it 30-60 minutes before activity on a light stomach, and adjust only under prescriber guidance. The maximum safe dose is 100 mg once per 24 hours, and exceeding this carries real risks. If the standard approach is not working, a clinical conversation is always more appropriate than self-adjusting.

FAQ

The DoktorABC medical advisory board

Dr. Roland Ruiken

Medical advisor, Norway

Dr. Viktor Simunovic

Medical advisor, Croatia

To the medical advisory board