Medically reviewed by Vicky Davis, FNP
Written by Our Editorial Team
Last updated 8/24/2022
Sildenafil, the active ingredient in Viagra®, is an FDA-approved medication for treating erectile dysfunction (ED).
Although sildenafil doesn’t cure erectile dysfunction, it does help to make it easier for you to get and maintain an erection when you’re sexually aroused, primarily by increasing blood flow to the tissue inside your penis.
Like many other medications for ED, sildenafil is available in several different dosages. Finding and using the right dose of sildenafil for you will help you get the best results while limiting your risk of side effects.
Below, we’ve explained how sildenafil works to treat ED and shared the most common dosages for this medication.
We’ve also provided some actionable tips to help you select the most effective dose of sildenafil dosage for your needs.
Sildenafil is the active ingredient Viagra. It’s available under several brand names and as a generic medication. Currently, sildenafil is approved by the FDA for erectile dysfunction and pulmonary arterial hypertension (PAH), a form of high blood pressure in the lungs.
Sildenafil comes in oral tablet form and is available in a range of dosages, from a lowest dose of 20mg up to 100mg.
It usually takes 30 minutes for sildenafil to start working. Most men who use sildenafil to treat ED take the medication 30 minutes to four hours before sexual activity.
Because ED can vary in severity, there’s no one-size-fits-all dose of sildenafil that treats erectile dysfunction in everyone. If you have mild to moderate ED, you may notice major improvements in your sexual performance from a relatively low dosage of sildenafil.
On the other hand, if you have severe erectile dysfunction, or erectile dysfunction that’s caused by a medical condition that limits blood flow to your penis, you may need to use a higher dosage.
While a higher dosage of sildenafil may be the most effective, taking too much sildenafil can also increase your risk of experiencing side effects.
Before we get into the specifics of sildenafil doses, it’s important to explain how sildenafil works as a treatment for erectile dysfunction.
Sildenafil was the first oral medication approved to treat ED. It came onto the market in 1998 as Viagra. In the decades since it first appeared, it’s also become available as a generic drug and is one of the most widely used prescription medications in the United States.
Sildenafil is part of a class of medications referred to as phosphodiesterase-5 (PDE5) inhibitors, or PDE5 inhibitors. It works by blocking the actions of cGMP-specific phosphodiesterase type 5 -- an enzyme that controls the flow of blood to certain types of tissue in your body.
Erections are all about blood flow. When you’re sexually aroused, your nervous system signals to the muscles of your penis. As these muscles relax, blood flows to the corpora cavernosa -- a pair of sponge-like masses of erectile tissue that allow you to get an erection.
PDE5 is responsible for regulating blood flow to your penis. By blocking the effects of PDE5 on blood flow, sildenafil improves the supply of blood to the erectile tissue in your penis and makes it easier to get and stay hard.
As blood flows in, the tunica albuginea -- a type of membrane that surrounds the erectile tissue of your penis -- contracts, trapping blood inside your erectile tissue and allowing you to maintain an erection during sex.
Although sildenafil can improve blood flow to your penis and make getting hard easier, it doesn’t cause you to feel sexually aroused or have any impact on your sex drive.
It also doesn’t cause spontaneous erections. For sildenafil to work, you’ll still need to have some form of sexual stimulation.
Sildenafil is available in several different dosages. The standard dosage for ED is 50mg, usually taken about one hour before sexual activity. This may be adjusted to 25mg or 100mg based on the severity of your ED and your response to sildenafil.
Some versions of sildenafil come in 20mg tablets. This dosage was originally developed to treat pulmonary hypertension, but is sometimes used off-label to treat ED.
There’s no “ideal” dosage of sildenafil for everyone. If you only have mild ED, you may find that a low dosage is more than enough to improve your symptoms and help you to have sex without worrying about getting or maintaining your erection.
On the other hand, if you have severe or persistent ED, your healthcare provider may prescribe sildenafil at a higher dosage.
We’ve listed the most common dosages of sildenafil below, along with more information on the effects you can expect from each one.
50mg is the most common dosage of sildenafil for erectile dysfunction. If you sometimes find it difficult to get or maintain an erection during sex, your healthcare provider may prescribe 50mg sildenafil to increase blood flow and improve your erections.
Most men with ED notice improvements in their erections and sexual performance from a 50mg dosage of sildenafil.
For example, a series of two studies looked at the effects of 50mg sildenafil in men with erectile dysfunction.
After taking sildenafil at this dosage, 71 percent of the men that took part in the study developed an erection in 30 minutes or less. After 45 minutes had passed, 82 percent of the men achieved an erection.
On average, the men’s erections lasted for a median time of 19.5 minutes after using sildenafil, compared to zero minutes for men that received a non-therapeutic placebo.
100mg is the maximum recommended dosage of sildenafil for ED. Your healthcare provider may prescribe sildenafil at this dosage if you have severe and/or persistent ED that doesn’t get better with the use of sildenafil at a lower dose.
Research shows that doses of sildenafil greater than 100mg don’t produce any improvements in erections or sexual performance, but do cause an increase in side effects.
25mg is the minimum dosage of sildenafil that’s approved to treat erectile dysfunction. You may be prescribed sildenafil at this dosage if you only have mild ED, or if you have any health issues that may increase your risk of side effects from sildenafil.
If you notice side effects from sildenafil at a dosage of 50mg or 100mg, your healthcare provider may suggest reducing your dosage to 25mg.
Some forms of sildenafil come as a 20mg tablet. These are often generic forms of Revatio® -- a version of sildenafil used to treat pulmonary arterial hypertension (PAH).
For most people, sildenafil is a safe and effective medication. However, like with all medications, it is possible for sildenafil to produce side effects. Most potential adverse effects of sildenafil are mild and transient, although some may be bothersome.
Common side effects of sildenafil include:
Myalgia (muscle pain)
Data from clinical studies shows that the risk of developing side effects from sildenafil increases with dosage.
For example, headache (the most common side effect of sildenafil) was reported by 16 percent of people at a dosage of 25mg, 21 percent at a dosage of 50mg and 28 percent at a dosage of 100mg in clinical trials.
Other side effects, such as flushing, indigestion, nasal congestion and others also occurred at a higher rate as the dosage of sildenafil increased.
If you’re prone to side effects from sildenafil, your healthcare provider might suggest taking your medication at a lower dosage, such as 25 or 50mg.
Like other medications, sildenafil can cause interactions when it’s used with other drugs, alcohol or other substances.
Sildenafil can potentially cause dangerous interactions when it’s used with medications for heart disease and/or high blood pressure.
More specifically, when sildenafil is used with nitrates, alpha-blockers or certain calcium channel blockers used to treat hypertension and/or cardiovascular disease, it can contribute to a sudden decrease in blood pressure that may, in some cases, be life threatening.
Some recreational drugs, such as poppers that contain ingredients such as amyl nitrate, amyl nitrite and/or butyl nitrate, can also cause potentially dangerous effects when used with PDE5 inhibitors such as sildenafil.
Medications that affect the enzyme CYP3A4 may contribute to higher levels of sildenafil in your bloodstream, potentially increasing your risk of side effects.
To reduce your risk of developing drug interactions, it’s important to tell your healthcare provider about any medications you currently use or have recently used before beginning treatment with sildenafil.
It’s also important to inform your healthcare provider if you have any underlying health issues, or if you’ve previously had heart problems such as a heart attack, irregular heartbeat, angina, pain that affects your chest or narrowing of your aortic valve.
Our guide to sildenafil interactions goes into greater detail about the risks of using sildenafil with other medications, as well as steps that you can take to lower your interaction risk.
Using the right dose of sildenafil can help to improve your results, all while reducing your risk of developing side effects. However, there’s more to using sildenafil effectively than just taking the correct dosage.
Try the following tips and techniques to improve your results from sildenafil:
Take sildenafil an hour before sex. Sildenafil typically needs 30 to 60 minutes to start working as a treatment for erectile dysfunction. For best results, try to use sildenafil an hour before you plan to have sex.
Avoid high-fat foods while using sildenafil. It’s okay to take sildenafil with food or on an empty stomach. However, it’s best to avoid taking it with a high-fat meal, as this may slow down absorption and make sildenafil take longer to work.
Limit your alcohol consumption. Although it’s generally okay to drink a small amount of alcohol while using sildenafil, drinking alcohol to excess can increase your risk of side effects.
Alcohol can also cause erectile dysfunction. Our guide to sildenafil and alcohol provides more information about the risks of drinking alcohol while using sildenafil.
Take other steps to improve your sexual health. In addition to using sildenafil, making simple changes to your daily habits can help to improve blood flow throughout your body and reduce your risk of experiencing sexual dysfunction.
Try to eat a healthy diet, maintain a body mass index (BMI) in the normal range, cut back on nicotine and get at least some daily exercise. Our list of natural ways to improve your erections shares other steps that you can take for better erectile health.
Consider reducing your porn consumption. It’s alright to watch porn occasionally, but excessive consumption of pornography could contribute to a form of erectile dysfunction referred to as “porn-induced ED.”
If you watch porn often and have noticed that your erections aren’t as firm or reliable as they used to be, try taking a break from porn to see if your erections improve naturally.
Although sildenafil was the first medication to come onto the market for erectile dysfunction, it’s far from the only option that’s available today.
Currently, three other oral medications have been approved by the FDA as treatment options for erectile dysfunction. Some of these medications last longer than sildenafil, while others are less likely to cause side effects.
Other medications for the treatment of erectile dysfunction include:
Tadalafil. The active ingredient in Cialis®, tadalafil is a long-lasting medication that can provide relief from ED for up to 36 hours per dose. It’s available for use as-needed and as a daily-use medication.
Vardenafil. The active ingredient in Levitra®, vardenafil typically lasts for slightly longer than sildenafil.
Avanafil. A new, second-generation ED medication, avanafil (sold as Stendra®) works quickly to improve blood flow to your penis and is less likely to cause some side effects than older medications for ED.
We offer several FDA-approved erectile dysfunction medications online, following a consultation with a physician who will determine if a prescription is appropriate.
Erectile dysfunction is a common problem that affects an estimated 30 million adult men in the United States alone. If you’re one of these men, using medication like sildenafil can help you to more easily maintain your erection and enjoy a fulfilling, satisfying sex life.
Since erectile dysfunction can vary in severity, there’s no single dose of sildenafil that works for everyone. Instead, your healthcare provider will choose your initial sildenafil dose based on the severity of your ED, your general health and other factors.
Most of the time, your healthcare provider will prescribe sildenafil at a dosage of either 25, 50 or 100mg for use as needed.
If the initial dosage you’re prescribed isn’t effective, or if you experience side effects, make sure to talk to your healthcare provider. It’s common and normal to adjust your sildenafil dosage over time to provide the best results with as few side effects as possible.
Interested in treating ED? Sildenafil is one of several medications for improving blood flow and making it easier to get and maintain an erection when you’re sexually aroused.
Our guide to erectile dysfunction goes into more detail about what causes ED, as well as what you can do to improve your sexual function. You can also learn more about sildenafil and other ED medications in our guide to the most common erectile dysfunction treatments and drugs.