Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 4/21/2023
Sildenafil, the active ingredient in Viagra®, is an FDA-approved medication for treating erectile dysfunction (ED). If you’re Googling dosages, you may have some misunderstandings about what it’ll do for you — and that’s okay.
Sildenafil has a reputation — a well-earned one — for helping people with ED. But it doesn’t do this by making you pitch tents like entry day at a music festival.
Sildenafil doesn’t cure erectile dysfunction at all, actually. There’s no “cure” for erectile dysfunction. What it does is help make it easier for you to get and maintain an erection when you’re already sexually aroused.
And importantly, your dosage will impact how effective it is at doing this.
Sildenafil is available in several dosages. Finding and using the right one for your needs will help you get the best results while limiting your risk of side effects.
Below, we’ll explain and share the most common dosages for this medication.
Like many other medications for ED, sildenafil helps primarily by increasing blood flow to the tissue inside your penis. Dosage isn’t based on penis size, SAT scores or your tax bracket — all that is false.
Here are the most important facts about sildenafil:
Sildenafil (the active ingredient in Viagra) is approved by the FDA for erectile dysfunction and pulmonary arterial hypertension (PAH), a form of high blood pressure in the lungs.
Sildenafil is part of a class of medications referred to as phosphodiesterase-5 (PDE5) inhibitors, or PDE5 inhibitors.
Sildenafil 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.
PDE5 is responsible for regulating blood flow to your penis. By blocking the effects of PDE5, sildenafil improves the supply of blood to the blood vessels and erectile tissue and makes it easier to get — and stay — hard.
Sildenafil comes in oral tablet form and is available in a range of dosages, from 20mg up to 100mg (milligrams).
It usually takes around 30 minutes for sildenafil to start working. Most men who use sildenafil to treat ED take the medication 30 minutes to one hour 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 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 most effective, taking too much sildenafil can also increase your risk of experiencing side effects.
Sildenafil is available in several dosages. The standard dosage for ED is 50mg, usually taken about one hour before sexual activity. This can be adjusted to 25mg or 100mg based on the severity of your ED and your response to the medication.
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.
Here’s what you can typically expect from a dosage of sildenafil:
Your journey with sildenafil or Viagra will probably begin with a 50mg dosage.
Since most men with ED notice improvements in their erections and sexual performance from a 50mg dosage, healthcare providers usually start there and either increase or decrease the dosage accordingly.
In a randomized trial, men’s erections lasted for 19.5 minutes (median) after using sildenafil, compared to zero minutes (median) for men who received a non-therapeutic placebo. We’ll gladly take 20 points over… Zero.
100mg is the maximum recommended dosage of sildenafil for ED. Your healthcare provider may prescribe sildenafil at this dosage if you have severe 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 approved to treat erectile dysfunction. You might be prescribed sildenafil at this dosage if you have mild ED or any health issues that may increase your risk of side effects from sildenafil.
Some forms of sildenafil come as a 20mg tablet. These are often generic forms of Revatio® — a version of sildenafil primarily used to treat PAH.
Let’s get something straight, fellas: the dose of sildenafil you use is not a measure of manhood. There’s no “ideal” dosage of sildenafil for everyone.
That said, 50mg has shown proven benefits for most men in clinical trials.
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 developed an erection in 30 minutes or less. After 45 minutes, 82 percent achieved an erection.
But dosages are dependent on your unique needs — not averages.
You may not want to take 50mg if you experience significant side effects. If you notice side effects from sildenafil at a dosage of 50mg or 100mg, your healthcare provider may suggest reducing your dosage to 25mg.
If you only have mild ED, you may find that a low dosage is more than enough to improve your symptoms and help you 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.
It’s that simple, and it’s important to view the situation from that viewpoint. Find the right dosage for you, and take what you need — nothing more, nothing less. We all need a little help sometimes, right?
For most people, sildenafil is a safe and effective medication, but that doesn’t mean it’s perfect. And like Superman around kryptonite, many of the negative effects you might experience from sildenafil can be dose-dependent.
Luckily, most potential adverse effects of sildenafil are mild and resolve on their own over time, although some may be bothersome.
Common side effects of sildenafil include:
Myalgia (muscle pain)
As we mentioned briefly above, clinical studies show that the risk of side effects from sildenafil increases with dosage.
For example, headaches (the most common side effect of sildenafil) were 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 and nasal congestion, also occurred at a higher rate as the dosage of sildenafil increased.
Sildenafil also causes some serious side effects like:
Priapism (persistent, painful erections)
Sudden loss of vision (retinitis pigmentosa)
Seriously, death — so make sure you use this medication as directed, and make sure you seek emergency medical help immediately if you experience any of the side effects above. Priapism — an erection lasting four hours or longer — sounds great until you realize you can permanently damage the tissue in your penis if you don’t do something about it ASAP.
Like other medications, sildenafil can cause interactions when used with drugs, alcohol or other substances.
Sildenafil can potentially cause dangerous drug interactions when used with medications for heart disease and/or high blood pressure.
Nitrates, alpha-blockers, calcium channel blockers. When sildenafil is used with these or other medications 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.
Recreational drugs. Some party drugs — such as poppers — containing 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.
Things that affect the CYP3A4 enzyme. Sildenafil citrate, Cialis (tadalafil), vardenafil and Levitra all have negative interactions with medications like itraconazole, ketoconazole, nitroglycerin and, oddly enough, grapefruit juice specifically. When consumed with sildenafil, these things affect the CYP3A4 enzyme and may contribute to higher levels of sildenafil in your bloodstream, potentially increasing your risk of side effects.
Make sure to tell your healthcare professional if you’re on any of these — a bad mixture could lead to low blood pressure that may actually kill you. If you take them together by accident, seek medical attention.
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.
Also, tell them if you have or have had sickle cell anemia, leukemia, sexually transmitted diseases or — just saying this to be safe — are breastfeeding.
Our guide to sildenafil interactions goes into greater detail about the risks of using sildenafil with other medications, as well as steps you can take to lower your interaction risk.
Erectile dysfunction is a common problem affecting 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 more easily maintain an erection and enjoy a fulfilling, satisfying sex life.
Sildenafil doesn’t cause sexual stimulation — it’s not just going to give you a four-hour tent pole. If it does, get to a hospital because it might be Priapism.
Since erectile dysfunction can vary in severity, no single dose of sildenafil 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 starting dose 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.
Don’t use supplements or other OTC (over-the-counter) pills for the treatment of erectile dysfunction. Prescription drugs are safe and FDA-approved.
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.
Let a professional worry about your dosage — you just focus on having the best sex of your life. And don’t forget to stretch!