Erectile dysfunction (ED) impacts at least 30 to 50 million men in the United States. The impact of ED goes beyond an inability to get or maintain an erection. ED can cause significant harm to your mental health due to loss of self-esteem, feelings of shame, anxiety, and depression, and negative impacts on your personal relationships.

Viagra® (sildenafil citrate) has been used for over 25 years to treat ED, rejuvenating sexual health and well-being for millions of people. In this guide, we’ll review Viagra and sildenafil (generic Viagra) dosages for erectile dysfunction. Understanding your dosage is key to getting the most out of Viagra to treat ED, and minimizing your risk for side effects.

Sildenafil as an ED treatment

Before we dive into dosage details about Viagra (sildenafil) as an ED treatment, let’s first review some fast facts on ED. It’s important to know why ED happens and how Viagra works to treat it.

Erectile dysfunction (ED) is an inability to get or maintain an erection suitable for sexual activity. It’s common in men over age 40, but also affects younger men as well. There are numerous causes for ED, and it’s often due to more than one variable.

The most obvious causes are organic issues, such as problems with blood flow to the penis, a drop in hormone levels, or an issue with penile smooth muscle tissue. For example, conditions such as heart disease and diabetes can disrupt erectile function. While not pleasant to think about, blood vessels in the penis are also susceptible to atherosclerotic plaques that we normally think of forming elsewhere.

ED can also be a side effect of prescribed medications such as many antidepressants and antihypertensives. An often underestimated cause of ED are psychological factors. Performance anxiety and depression are strong contributors, particularly in men under 40 affected by ED.

Regardless of the cause, our treatment goal for ED is simple: to help you have and maintain an erection suitable for sex. Viagra contains the active ingredient sildenafil. It’s a type of medication called a phosphodiesterase type 5 (PDE5) inhibitor. It works to treat ED by relaxing penile smooth muscle and improving blood flow to the penis when you’re aroused. In the absence of sexual stimulation, Viagra won’t have an effect at recommended dosages.

Is Viagra used long term?

Yes, Viagra is used long term. After all, Viagra is a treatment for ED - not a cure. Your ED symptoms will likely return if you stop treatment.

Viagra was first approved in 1998, and millions of people have used it to treat ED since. Based on experience to date, sildenafil appears safe to take long term.

And it appears that Viagra still works when used long term, which (obviously) matters too. One study followed over 900 participants who, on average, took Viagra for 4.5 years. Over 94% of participants answered “yes” to the question, “Are you satisfied with the effect of treatment on your erections?”.

Common Viagra dosages explained

Viagra comes as an oral tablet that you swallow. For most, the recommended starting Viagra dosage is 50 mg, taken once daily as needed about 1 hour before sex. “1 hour before sex” is more of a general guideline, though - you can take Viagra anywhere from 30 minutes to 4 hours before sexual activity.

Let’s quickly clarify what “as needed” means - or more importantly, what it does not mean. “As needed” means you don’t need to take Viagra every day for it to work. And you don’t need to take it at a certain time of day.

But “as needed” does not mean you can simply take it as many times as you like. You should not take Viagra more than once per day.

If the 50-mg dosage isn’t working for you, your doctor may increase it to the maximum dosage of 100 mg once daily as needed. On the other hand, if the 50-mg dosage works to treat ED but you have side effects, you may need a dose reduction to 25-mg once daily as needed.

Here’s a quick summary on common Viagra dosages. These are also the recommended dosages for sildenafil (generic Viagra). Talk with your doctor if you have questions or concerns about your Viagra dosage.

Factors affecting dosage

Certain factors affect the Viagra dosage or sildenafil prescribed by your doctor. Weight doesn’t play a role, but your age might.

Looking at recommended Viagra dosages by age, your doctor may prescribe a 25-mg starting dosage if you’re over age 65. Why? As we age, our body handles medications differently. And studies show that above age 65, Viagra reaches a higher level in your system after taking a dose compared to what happens in people aged 65 and under.

“A higher level of Viagra means better erections, right?” No, it doesn’t exactly work like that. But a higher Viagra level in your system does increase your risk for side effects, including serious ones (which are discussed later in this article).

Other factors affecting your Viagra dosage include having a condition affecting your liver (such as cirrhosis) or a severe problem with your kidney function (such as end-stage kidney disease). Your body relies on your liver to metabolize (break down) Viagra after you take a dose, and on your kidneys to remove the medication from your system. Having a liver or kidney condition can mean you need a lower Viagra dosage to safely use the medication.

There are also drug interactions with Viagra that can affect the dosage your doctor prescribes. Check out the “Viagra Interactions” section to learn more.

Viagra dosage safety: what you need to know

“If 50 mg is the starting dose of Viagra, then 100 mg must be even better, right?” Not exactly.

A higher dosage of Viagra may increase your risk for side effects. And, it’s not guaranteed to work “better” at treating ED. Which is why it's important to follow the dosing directions from your doctor.

In this section, we discuss what you need to know about how to use Viagra safely. If you have concerns about whether your dose is working for you, let your doctor know. Dosage adjustments should not be made on your own.

How often can you take Viagra?

The maximum dose of sildenafil in 24 hours is 100 mg. It’s important to note, though, that there’s also a limit to how often you can take it.

You should not take Viagra or sildenafil (generic Viagra) more than once per day, even if your dose is below 100 mg.

Viagra begins working in about 30 minutes, but its effects last up to 18 hours. Keep in mind that you can take Viagra between 30 minutes and 4 hours before sex. So you may not have true “around the clock” coverage, but it’s pretty close.

What if Viagra doesn’t work for my symptoms? Can I take more?

No, you should not take more Viagra or sildenafil if you do not experience ED relief from one dose. As discussed in the following sections, there is such a thing as taking too much Viagra. This includes taking more than one dose in a day.

How much Viagra is too much?

The maximum Viagra dosage recommended is 100 mg once per day.

Taking too much Viagra or sildenafil can cause side effects. This often means mild side effects, such as flushing, headache, and indigestion. But too much Viagra can also cause serious side effects. Which leads us to..

What happens if you take too much Viagra?

When it comes to Viagra, more is not better. Quite the opposite: taking too much Viagra may quickly turn an intimate moment into a medical emergency.

Taking too much Viagra can cause the same side effects as recommended dosages. But you’re more likely to have side effects, and symptoms are more likely to be severe. For example, taking too much Viagra can cause:

• Low blood pressure, including dangerously low blood pressure
• Prolonged erection and priapism (a painful erection lasting longer than 6 hours). The “See a doctor if you have an erection that lasts longer than four hours” bit from Viagra commercials refers to this side effect. There’s a reason commercials focus on it - prolonged erections require immediate treatment. Without prompt medical attention, priapism can damage your penis and put a permanent end to your ability to get an erection.
• Vision problems, including sudden vision loss in one or both eyes.
• Hearing problems, including tinnitus and sudden hearing loss.

If you think you’ve taken too much Viagra, immediately contact your healthcare provider. But if your symptoms feel severe, call 911 or go to the closest emergency room.

Viagra interactions

Viagra and generic Viagra have both minor and major interactions with other medications.

Major Viagra interactions include:

• Other phosphodiesterase type 5 (PDE5) inhibitors, such as tadalafil (Cialis). Taking other PDE5 inhibitors with Viagra raises your risk of side effects.
• Nitrates, such as nitroglycerin (Nitrostat)
• Antihypertensives, such as lisinopril, carvedilol, amlodipine, or valsartan
• Alpha blockers, such as prazosin, tamsulosin, and doxazosin
• “Poppers” (recreational nitrites such as amyl nitrite)
• Certain antifungal medications, such as ketoconazole and itraconazole
• Certain antibiotics, such as clarithromycin and erythromycin
• Protease inhibitors for HIV, such as ritonavir and saquinavir

Different interactions have differing severities. For example, there’s no safe Viagra dosage to take with nitrates, as this combination can cause dangerously low blood pressure.

On the other hand, it may be safe to take a lower Viagra dose if you’re also taking saquinavir or an alpha blocker like doxazosin. But the final call is between you and your healthcare provider.

Viagra (sildenafil) common side effects

Viagra and sildenafil have a proven track record at treating ED. But like most medications, it can cause side effects (also called adverse effects). Thankfully, Viagra’s common side effects are often mild. They may go away with a lower dosage, or may even go away on their own as you continue taking Viagra.

Common side effects of Viagra include:

• Headache
• Flushing
• Indigestion
• Vision problems, most common are changes to your color vision or blurred vision
• Stuffy nose
• Pain in your back or muscles
• Nausea
• Dizziness

Reach out to your healthcare provider if you have any of the side effects above and they don’t go away on their own in a few hours or days.

What’s the dosage of Cialis vs. Viagra?

Cialis (tadalafil) and Viagra are both phosphodiesterase type 2 (PDE5) inhibitors used to treat ED. Since they’re both ED medications, you may wonder how their dosages compare.

The lowest dose recommended for Cialis is 5 mg, while Viagra’s lowest dose is 25 mg. But this doesn’t mean Viagra is “stronger” than Cialis. Yes, 25 is a larger number than 5. But that’s not a proper way to compare drug dosages. 1 mg of Cialis is not equivalent to 1 mg of Viagra and vice versa.

The table below compares common dosages of Cialis vs. Viagra when used as needed.

It’s important to note that, unlike Viagra, Cialis also has once-daily dosing for ED. With this dosing, you take Cialis without timing it around sexual activity. When Cialis is prescribed in this manner, the typical dose is 2.5 mg taken once daily. This dose may be increased to 5 mg once daily.

Talk with your healthcare professional if you’d like to know more about how Cialis and Viagra compare. They can provide medical advice on how ED medications are alike and differ.

When to talk to your doctor about your sildenafil dose

You should ask your healthcare professional for medical advice any time you have questions about your sildenafil (generic Viagra) dose. Remember, they’re invested in your health and are there to be a resource for you.

That said, what are some situations when you’d want to talk with your doctor about your sildenafil dose?

• If you think your dose isn’t working for you. If your Viagra dose doesn’t work for your ED symptoms, let your healthcare provider know. They can determine if your dosage should be increased. Do not change your dose on your own! Work with your doctor to find a dosage that works for you. Your doctor can also determine whether other ED medications, such as different PDE5 inhibitors, should be tried if Viagra isn’t working.
• If you have bothersome side effects that don’t go away. Let your healthcare provider know if you have mild side effects of sildenafil, such as headache or indigestion, that don’t go away. Prescribing a lower dosage may alleviate your symptoms.
• If you start taking a new medication or supplement. Certain prescription drugs and even over-the-counter medications or supplements can interact with Viagra, which can make Viagra less effective or raise your risk for side effects.
• If you’re diagnosed with any new medical condition. Certain medical conditions can raise your risk for side effects of Viagra. Let your doctor know if you receive a new diagnosis while taking Viagra, especially for any condition involving your kidneys or liver.

Now, let’s address some commonly asked questions about Viagra (sildenafil) dosages.