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Understanding Sildenafil Dosage
Understanding Sildenafil Dosage
Dr. Zoë Lees (PhD)
Dr. Sophie Dix (BSc, PhD)
17 June 2024 | Updated: 4 August 2026
4 August 2026
Interested in trying Sildenafil for erectile dysfunction? It's one of the most popular treatment options, helping millions of men worldwide have improved erections. Different doses work differently for different men, and it's important you find the right one so you can get the results you want. This is our guide to each Sildenafil dose, how they differ and who they're suitable for.
What is Sildenafil?
Sildenafil is a medicine that belongs to a class of drugs known as PDE5 inhibitors. Its most common use is in the treatment of erectile dysfunction, but it's also sometimes used to treat pulmonary arterial hypertension (high blood pressure in the blood vessels around your lungs). Sildenafil is also the active ingredient in the well known brand-name drug Viagra.
How does Sildenafil treat erectile dysfunction?
Sildenafil and other PDE5 inhibitors treat erectile dysfunction by encouraging smooth muscle relaxation and increasing blood flow to the blood vessels of your penis during sexual stimulation. This makes it easier to get and maintain erections when you’re aroused. 80% of men find that they experience improved erections when they take Sildenafil. [1]
Which Sildenafil dosage should I take?
There are three doses of Sildenafil you can take: 25 mg, 50 mg, 100 mg. Each dose of Sildenafil works in just 30 to 60 minutes and lasts for four hours on average.
Here's a quick guide to each one:
50mg
This is the usual starting dose for erectile dysfunction treatment. Research shows that this dose is effective in almost three-quarters of men [2], but you can switch to a higher or lower dose if this one isn't right for you.
You should try Sildenafil 50 mg a few times, exactly as recommended, before deciding whether it works for you. If you don't get the desired results, speak to your clinical team about switching to the higher 100 mg dose or a different drug, such as Tadalafil.
25mg
25 mg is the lowest Sildenafil dose. You may be prescribed it if you take other prescription drugs to reduce the risk of drug interactions or adverse effects. This dose may also be for you if you experienced side effects with the 50 mg dose. If you feel like you need to increase your dose, speak to your clinical team to see if it's safe to take a higher strength.
100mg
This is the maximum dose of Sildenafil. Mild side effects are more likely with this dose. If you try 100 mg and still don't have don't have improved erections, you should speak to your doctor to explore other treatment options.
How to take Sildenafil
Every dose of Sildenafil takes the same amount of time to start working. We recommend taking one pill around 30 to 60 minutes before you plan to have sex to give your body plenty of time to absorb the medication.
Does Sildenafil have side effects?
Like all medications, Sildenafil can cause some side effects. These tend to be mild and, as we've previously mentioned, can vary in intensity based on your dosage.
Common side effects include:
- Headaches
- Muscle aches
- Back pain
- Facial flushing
- Indigestion
Seek medical attention immediately if you notice severe adverse effects, including: chest pain, loss of vision, a sudden drop in blood pressure, seizures, prolonged or painful erection, hearing loss or an allergic reaction.
How to get treatment for erectile dysfunction
Sildenafil and other medications for erectile dysfunction need to be prescribed by a healthcare professional to make sure they're the right treatment for you.
Want to start having improved erections? Find out what treatment is suitable for you on MedExpress.
References
- Goldstein I, Tseng LJ, Creanga D, Stecher V, Kaminetsky JC. Efficacy and Safety of Sildenafil by Age in Men With Erectile Dysfunction. The Journal of Sexual Medicine. 2016 May;13(5):852–9.
- Sildenafil 100 mg film-coated tablets - Summary of Product Characteristics (SmPC) - (emc) [Internet]. www.medicines.org.uk. Available from: https://www.medicines.org.uk/emc/product/7124/smpc
Next scheduled review date: 4 August 2029
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Authors
Written by: Dr. Zoë Lees (PhD)
Dr. Zoë Lees is a medical writer at MedExpress specialising in obesity and health communication. She completed her PhD at the University of Glasgow, where she investigated adipose tissue (fat tissue) function in pregnancies complicated by pre-eclampsia and gestational diabetes. Her work focuses on translating complex clinical evidence into clear, engaging and evidence-based health information for patients and the public. At MedExpress, Zoë contributes to clinical content, educational resources and media communications across areas including weight management, GLP-1 therapies and metabolic disease. Zoë is particularly interested in improving public understanding of obesity as a chronic condition and ensuring patients have access to accurate, accessible health information grounded in current scientific evidence.
Medically reviewed by: Dr. Sophie Dix (BSc, PhD)
Dr. Sophie Dix is Head of Medical Affairs at MedExpress. A behavioural neuroscientist by training, Sophie has spent 30 years working at the intersection of medical research, pharmacology, technology and patient communication across the pharmaceutical industry, health technology and charity sectors. At MedExpress, Sophie's role is to ensure that everything the organisation does is grounded in the most current science. That means translating complex clinical evidence into accessible health information across the website, clinical pathways and media communications. It also means working with external press and broadcast media as a named expert commentator, making the science behind weight management and GLP-1 treatments understandable to a general audience. A core part of Sophie's work is building MedExpress's Real-World Evidence (RWE) programme: learning systematically from patient outcomes to understand what works in practice, not just in clinical trials. This patient-level insight feeds directly into improving patient experience and health outcomes. Sophie believes that patients make better decisions when they have access to accurate, evidence-based information. As an advocate for meaningful change in how obesity is understood, Sophie works to reduce stigma and raise awareness of the condition as an illness. This includes reframing the conversation around GLP-1s from aesthetics to public health, while highlighting the health benefits of weight loss and weight management.
Note from the experts
Remember: This blog shouldn’t be regarded as medical advice, diagnosis, or treatment. We make sure everything we publish is fact checked by clinical experts and regularly reviewed, but it may not always reflect the most recent health guidelines. Always speak to your doctor about any health concerns you have.