The proper dosage for sildenafil (Viagra) will vary between 25mg and 100mg once daily, with the most prescribed dosage being 50mg. Patients generally start with a lower dosage of 25mg to 50mg and depending on how the starting dosage works including how well it interacts with the body, may move to a higher dosage for a better experience. (1)
For treating erectile dysfunction (or ED), sildenafil is normally only taken on an as needed basis, 30-60 minutes before sexual activity but can be dosed between 30 minutes and 4 hours before sexual activity.
How Sildenafil Works to Treat ED
Sildenafil treats erectile dysfunction by selectively inhibiting an enzyme known as phosphodiesterase type 5, which allows corpus cavernosum smooth muscle to relax, making erections during sexual stimulation more satisfactory. (2)
An erection is achieved in a response cycle that begins with sildenafil producing arteriolar dilatation and increased blood flow to the erectile tissue of the penis. (3)
In a study on different dosages for treating erectile dysfunction with sildenafil, it was found that both 50 mg and 100 mg doses of sildenafil improved erectile function, sexual satisfaction, and enjoyment in patients, however the 100 mg dose had slightly better results. Higher doses led to improved sexual frequency and enjoyment, especially for patients with more severe cases of ED or if the patient had any additional health conditions. The overall findings suggest that adjusting the sildenafil dosage can optimize treatment for an improved outcome and many patients who start at 50mg, request a higher dosage later on.
What Are the Available Sildenafil Dosages?
The common tablet dosages for sildenafil when treating erectile dysfunction are 25mg, 50mg, and 100mg with 50mg being the dosage most often initially prescribed and with dosages designed for once daily dosing. (4)
Professor Irwin Goldstein noted in a presentation on sildenafil in 2003 that taking a quarter pill of sildenafil every night was effective in preventing erectile dysfunction.
“If you would like to be sexually active in five years' time, take a quarter of a pill a night, we have data to show that will facilitate and prolong nocturnal erections.”
Dr. Irwin Goldstein
Speak with your doctor if you have been taking sildenafil as needed and want to try switching to a daily micro dose.
Sildenafil is considered generally a low-risk drug (although there are some important adverse effects and some contra-indications to taking sildenafil) and has been approved by the FDA (Food and Drug Administration) since 1998 for treating erectile dysfunction.
Starting Sildenafil: Recommended First-Time Dosage
Sildenafil prescriptions for erectile dysfunction typically start at 50mg and should be taken no more than once per day. (5) This recommended dosage was arrived at when studying different dosages in 532 different men with ED over a 24-week period with doctors escalating the dosage in 329 men to study the tolerance and efficacy of the drug. (6)
The results showed that doctors can start at 50mg and then if a patient finds that the 50mg pill is not effective enough, they can double the dosage. If side effects occur with the 50mg dosage, patients can have their prescription cut in half to 25mg or another medication such as tadalafil (Cialis) may be prescribed.
Adjusting Your Sildenafil Dosage Over Time
Adjusting your dosage can be important for both maximizing the intended effects and avoiding side effects. If your erections are weak or inconsistent, then speak to your doctor about possibly increasing the dose. If you experience any headaches, vision problems, dizziness, or low blood pressure, then you may need to lower your dosage.
Erections that last more than 4 hours is known as priapism, and is a serious medical condition for which you should seek immediate medical attention including visiting an emergency or urgent care facility.
Your doctor should monitor how you react to your initially prescribed dosage. If the the starting dosage for example is 50mg, and is effective, no changes are necessary. However, keep track of any notable differences or side effects that might occur, just in case. One study concluded that through counselling and dose customization, many men found improved satisfaction rates when being treated for the first time with PDE-5 inhibitors such as sildenafil.
Is 20 or 25mg Sildenafil Enough for ED?
25mg is not a normally the initially prescribed dosage of sildenafil, but if your doctor prescribes the low dose for any reason, achieving an erection is still possible. Doctors have found during a study that at an even lower dosage of 20mg sildenafil taken under the tongue (sublingual), 65% of men were able to have satisfactory results. (7)
However, the efficacy of sildenafil generally increases with dosage, with 82% of men having great results at 100mg.
Most studies focus on 25-100mg dosages, but if your doctor thinks a lower dosage is the best option for you based on your medical profile, there is still a chance you can get the results you want.
What Is the Maximum Safe Sildenafil Dosage?
The maximum FDA approved dosage for sildenafil is 100mg per day. Studies show that moving from 25mg to 50mg and then to 100mg doses produces better results and that going above that threshold has no benefit and only increases the risk of side effects. (8)
Comparing Sildenafil vs. Tadalafil Dosage
Tadalafil and sildenafil come in different doses, and this is because the different dosages have different results. Sildenafil is available in 25, 50, and 100 mg doses because it is taken as needed and generally lasts 4-6 hours. Tadalafil comes in 2.5mg and 5mg versions for daily use, and 10mg and 20mg doses for taking as needed. The daily use doses (2.5mg and 5mg) should be taken daily in the morning, or at bedtime, while the as needed doses (10mg and 20mg) are generally taken about 30-60 minutes before sexual activity. Tadalafil is often referred to as “the weekend pill” as when taken even as needed,, will be effective for up to 36 hours. (9)
When and How to Take Sildenafil for Best Results
For best results men should take sildenafil 30-60 minutes before sexual activity. However it can be effective when taken up to 4 hours before, but its effectiveness peaks at about an hour after use.
To maximize the effectiveness of the medication, it’s best to take it on an empty stomach. A high fat meal can delay absorption by up to an hour and reduce the peak concentration of the medication by almost 30%. (10)
Factors That Influence the Right Dosage for You
There are many factors that your doctor will evaluate when deciding on your ideal sildenafil dosage. Your age is an important factor and men over 65 for example, will likely start at a 25mg dosage before testing 50mg. Weight is generally not a direct factor in how well sildenafil will work, but low fitness levels or more severe ED may require patients to try a higher dose. Anyone with liver or kidney issues will also likely be started at the lower 25mg dose. You should discuss starting dose with your doctor as various factors may play into the choice of dosage.
If you have stable heart disease, you can generally still take sildenafil, but your blood pressure should be monitored and in some cases, an exercise stress test might be administered prior to starting sildenafil. Men with significant coronary artery disease or with valvular narrowing's in the heart caused by aortic valve stenosis or hypertrophic obstructive cardiomyopathy (or HOCM) should not use sildenafil. In some cases men with eye problems such as retinitis pigmentosa, extra caution should be taken since the drug can have visual side effects. (11)
Any man taking sildenafil for erectile dysfunction should be aware that drug interactions are one of the more important factors when deciding on whether the medication can be used safely and what dosage is safe.
Nitrates can cause issues with blood pressure, alpha blockers can increase the risk of dizziness, CYP3A4 inhibitors such as ketoconazole, erythromycin, or ritonavir can slow the breakdown of the certain medications such as sildenafil in the blood and in these situations, your doctor will discuss whether sildenafil is safe and if so, what the safe dose and administration routine (eg daily or every second day) are. Grapefruit juice is a mild inhibitor of an enzyme known as CYP3A4 and can increase the risk of side effects with sildenafil as this medication is metabolized by CYP3A4
Whether you’re taking 25mg or 100mg, always tell your doctor about any other medications you’re taking, even if they’re over the counter.
Conclusion
There is no perfect dosage of sildenafil for every man. 50mg is the most prescribed dose, but depending on the factors discussed in this article there may be a better dose for you based on your specific medical background and needs. Our doctors can evaluate your medical history based on your answers during our telehealth questionnaire and provide you with the right dosage of sildenafil for your specific medical profile.
FAQs About Sildenafil Dosage
*This is an AI generated FAQ summarizing key points in this article
What’s the best sildenafil dosage for beginners?
For most healthy adults, the recommended starting sildenafil dosage is 50 mg taken about 30–60 minutes before sexual activity. Depending on your response and side effects, a doctor may adjust your sildenafil citrate dosage down to 25 mg or up to 100 mg
Is 20 mg of sildenafil effective for ED?
Standard tablets for erectile dysfunction are 25 mg, 50 mg, and 100 mg. A sildenafil 20 mg dosage is primarily manufactured for pulmonary hypertension (Revatio). While 20 mg may help some men—especially in sublingual forms—many patients need higher doses for consistent results
Can I take sildenafil every day?
Sildenafil is generally intended for on‑demand use, not as a sildenafil daily dosage. Unlike tadalafil, there is no FDA‑approved daily sildenafil regimen. Taking it more than once in 24 hours can increase the risk of side effects and should be avoided unless prescribed by your doctor to be used that way.
What happens if I take too much sildenafil?
Exceeding the maximum dosage for sildenafil (more than 100 mg in 24 hours) does not improve erections and raises the risk of severe headaches, dizziness, low blood pressure, vision changes, and priapism (a prolonged erection requiring emergency care). Seek medical attention if you exceed the recommended daily maximum of 100mg in one day.
What’s the difference between sildenafil 50 mg and 100 mg?
Both doses work by improving blood flow, but the sildenafil 100 mg dosage is usually prescribed if 50 mg is not effective. Studies show a higher response rate at 100 mg, but also a greater chance of side effects. Doctors typically start at 50 mg and only increase to 100 mg if needed.
References:
How and when to take sildenafil. (2025, March). NHS. https://www.nhs.uk/medicines/sildenafil-viagra/how-and-when-to-take-sildenafil/
Loran, O. B., Ströberg, P., Lee, S. W., Park, N. C., Kim, S.-W., Tseng, L.-J., Collins, S., & Stecher, V. J. (2009). Sildenafil citrate 100 mg starting dose in men with erectile dysfunction in an international, double-blind, placebo-controlled study: Effect on the sexual experience and reducing feelings of anxiety about the next intercourse attempt. The Journal of Sexual Medicine, 6(10), 2826–2835. https://doi.org/10.1111/j.1743-6109.2009.01428.x
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Li, H., Bai, G., Zhang, X., Shi, B., Liu, D., Jiang, H., Ji, Z., Davis, M. R., Zhu, Z., & Fang, Y. (2015). Effects of two different dosages of sildenafil on patients with erectile dysfunction. American Journal of Men’s Health, 11(3), 747–757. https://doi.org/10.1177/1557988315620467
Smith, B. P., & Babos, M. (2023, February). [Article title]. https://pmc.ncbi.nlm.nih.gov/articles/PMC5675238/
Urologist recommends daily Viagra to prevent impotence. (n.d.). https://pmc.ncbi.nlm.nih.gov/articles/PMC1124975/
Goldstein, I., Lue, T. F., Padma-Nathan, H., Rosen, R. C., Steers, W. D., & Wicker, P. A. (1998). Oral sildenafil in the treatment of erectile dysfunction. The New England Journal of Medicine, 338(20), 1397–1404. https://doi.org/10.1056/NEJM199805143382001
McCullough, A. R., Carson, C. C., & Hatzichristou, D. (2006). A prospective study of the beneficial effects of dose optimization and customized instructions on patient satisfaction with sildenafil citrate (Viagra) for erectile dysfunction. International Journal of Impotence Research, 18(5), 389–394. https://doi.org/10.1038/sj.ijir.3901445
Deveci, S., Peşkircioğlu, L., Aygün, C., Tekin, M. I., Dirim, A., & Ozkardeş, H. (2004). Sublingual sildenafil in the treatment of erectile dysfunction: Faster onset of action with less dose. International Journal of Urology, 11(11), 989–993. https://doi.org/10.1111/j.1442-2042.2004.00925.x
Pfizer Inc. (2014). VIAGRA® (sildenafil citrate) tablets, for oral use [Label]. Initial U.S. Approval: 1998. https://www.accessdata.fda.gov/drugsatfda_docs/label/2014/20895s039s042lbl.pdf
Görge, G., Flüchter, S., Kirstein, M., & Kunz, T. (2003). Sex, erectile dysfunction, and the heart: A growing problem. Herz, 28(4), 284–290. https://doi.org/10.1007/s00059-003-2478-8
Tadalafil. (n.d.). In Wikipedia. https://en.wikipedia.org/wiki/Tadalafil
Huang, S. A., & Lie, J. D. (2013). Phosphodiesterase‑5 (PDE5) inhibitors in the management of erectile dysfunction. Pharmacy and Therapeutics, 38(7), 407–419. https://pmc.ncbi.nlm.nih.gov/articles/PMC3776492/
Kloner, R. A., & Zusman, R. M. (1999). Cardiovascular effects of sildenafil citrate and recommendations for its use. American Journal of Cardiology, 84(5), 11N–17N. https://doi.org/10.1016/S0002-9149(99)00438-7
