How long does Viagra last and when does it start to work?

Erectile dysfunction (ED)—when a person experiences trouble getting or maintaining an erection—can be stressful, and worrying about how long Viagra lasts will not help the situation. Typically, Viagra—a medication healthcare providers prescribe to treat ED—lasts for about 4–5 hours, but because erectile dysfunction is so common, affecting 30–50 million people in the U.S., this time-frame is not one-size-fits-all. Several factors can come into play to determine both how long Viagra takes to work and how long it lasts (Sooriyamoorthy, 2022). 

Read on to learn more about the timing of this effective drug.

Erectile dysfunction (ED)—when a person experiences trouble getting or maintaining an erection—can be stressful, and worrying about how long Viagra lasts will not help the situation. Typically, Viagra—a medication healthcare providers prescribe to treat ED—lasts for about 4–5 hours, but because erectile dysfunction is so common, affecting 30–50 million people in the U.S., this time-frame is not one-size-fits-all. Several factors can come into play to determine both how long Viagra takes to work and how long it lasts (Sooriyamoorthy, 2022). 

Read on to learn more about the timing of this effective drug.  

It's important to remember that you don’t need to have an erection for Viagra to work. Viagra’s active ingredient is sildenafil citrate, a PDE5 inhibitor that relaxes muscles in the penis and improves blood flow in order to enable people with penises to have erections. It is neither required nor healthy to have an erection the entire time Viagra is in your system (Smith, 2022).

Viagra can stay active in your system for up to 4–5 hours, depending on other factors. Most healthcare providers suggest that you take it 30–60 minutes before engaging in sexual activity, but you can take it up to four hours before intercourse. Some of the medicine may be in your body longer but in concentrations too low to cause any effect (Zucchi, 2019; DailyMed, 2017). 

Many different factors affect how long Viagra works for someone, including the dose of the medication, other medications or supplements you're taking, and your age, diet, overall health, and psychological state.

Viagra starts working in as little as 30 minutes after taking it. But it can take up to two hours to be effective if you take the drug with a meal (Zucchi, 2019).

So, how does it work? A lot has to go right in your body for an erection to happen. Even if we ignore the mental and emotional aspects of arousal and how they can lower sex drive, it's a complicated dance physiologically involving many systems of your body. 

A messenger called cGMP tells erectile tissue to relax, which allows blood to flow into the penis. But at the same time, the blood vessels that take the blood back to your heart constrict so that more blood is trapped in the penis. An enzyme called phosphodiesterase-5 (PDE-5) breaks down cGMP so that the erect penis can relax (Smith, 2022). 

That's where Viagra comes in. Viagra is a PDE-5 inhibitor, so it blocks this enzyme from breaking down the messenger that kick-starts the blood flow needed to get and maintain an erection (Smith, 2022). The medication doesn't just cause spontaneous erections on its own, though—it just makes them easier to form. You'll still also need to be sexually aroused to get an erection.

Timing is essential when it comes to taking Viagra. As mentioned, you should ideally take Viagra about 30–60 minutes before sex for maximum effect. You can take Viagra with or without food, but know that fatty foods decrease drug absorption and increase how long sildenafil takes to start working—meaning taking sildenafil on an empty stomach may allow it to work faster (Zucchi, 2019). 

If you think it is not working after 30–60 minutes, do not take more medication. There is an association between higher doses and higher rates of side effects. Talk to your healthcare provider if you feel like your Viagra or sildenafil is not working for you.

What is sublingual or compounded Viagra?

You might have heard about compounded ED medications that are taken under the tongue (sublingual), rather than being swallowed. When it comes to compounded ED treatments, mixing different ingredients—such as sildenafil and tadalafil—and putting them in a sublingual formulation is a unique treatment option for ED. The medication is absorbed directly into the bloodstream via the blood vessels under the tongue, rather than getting absorbed in the stomach, and small studies have shown that sublingual formulations work faster than traditional ED pills. 

Viagra (or generic sildenafil) tablets typically come in three doses: 25 mg, 50 mg, and 100 mg. 

It's most common for people to start with the 50 mg dosage. If you're on a higher dose, the effects of Viagra may last longer. It may take more time for older people to eliminate Viagra from their bodies, meaning the medicine may last longer in their bodies. This may also be the case for people with medical conditions like liver or kidney disease (DailyMed, 2017).

The most common side effects of Viagra include (Smith, 2022):

• Headaches

• Facial flushing

• Indigestion/heartburn 

• Back pain

• Stuffy nose

• Nausea 

Priapism, a persistent and painful erection that can last more than four hours, is the most infamous potential side effect of Viagra—fortunately, it is not a common one. But priapism is a serious health condition that requires immediate medical attention. You should follow medical advice on your recommended dose of Viagra and not take more if it doesn't work in 30 minutes (Smith, 2022). 

Other serious but less common side effects include hearing loss (which can be sudden), severe low blood pressure, and vision loss, which can be in one or both eyes (Smith, 2022).

Some medical conditions can interact negatively with Viagra. If you have any of the following, speak with your healthcare provider before taking Viagra. 

Blood pressure issues

Viagra relaxes the muscles of your blood vessels to improve blood flow. However, this can also cause low blood pressure. If your blood pressure drops too low, you can develop hypotension and may experience fainting, dizziness, etc. You should not take Viagra if you already have low blood pressure, as Viagra may worsen the condition.  

Similarly, if you have high blood pressure (hypertension) and use medications to lower it (antihypertensives), taking Viagra can cause your blood pressure to drop even further. This is especially true if you are taking an alpha-blocker antihypertensive, like terazosin. Alpha-blockers like tamsulosin (brand name Flomax) are also used to treat prostate issues and can have the same low blood pressure effect if taken with Viagra (DailyMed, 2017). 

Heart problems

People with heart conditions, such as a history of a recent stroke, heart attack, or chest pain, should check with their healthcare provider before taking Viagra (DailyMed, 2017). 

Vision concerns

Viagra may increase your risk of vision loss due to non-arteritic ischemic optic neuropathy (NAION), essentially a small stroke to the optic nerve. If you have a history of or risk factors for NAION, you should use caution with Viagra. Viagra has also been reported to cause changes in color vision in some people (DailyMed, 2017).

Lastly, anyone with an allergy or hypersensitivity reaction to Viagra should not use the medication.

Before starting Viagra or sildenafil, be sure to tell your healthcare provider about any other medications you are taking to avoid potential drug interactions. Some drugs, in particular, include:

• Nitrates: Viagra is contraindicated if you are also taking nitrates (e.g., nitroglycerin) for your chest pain. The combination of these two drugs can make your blood pressure drop to life-threatening low levels. You need to wait at least 24 hours after taking Viagra before you can safely take nitrates (Smith, 2022). 

• Ritonavir: Ritonavir affects the CYP3A4 enzyme in the liver—this is the system responsible for breaking down sildenafil. If taken with Viagra, ritonavir may raise Viagra concentrations in your blood and increase your risk of side effects like low blood pressure and prolonged erections (DailyMed, 2017).  

• PDE5 inhibitors: You should not combine sildenafil with other PDE5 inhibitors (like Revatio for pulmonary hypertension) or other erectile dysfunction treatments (like Cialis, Levitra, etc.) to avoid the potential risk of a drop in blood pressure (DailyMed, 2017). 

Common alternatives to Viagra include Cialis (tadalafil) and Levitra (vardenafil). If taking a pill before sexual activity doesn't work for you, daily Cialis may be an option. Taken daily, this medication provides a low dose of tadalafil to be ready for sex anytime. Levitra acts similarly to Viagra and, like the blue pill, needs to be taken within a timeframe before sexual activity (Zucchi, 2019).

In some cases, erectile dysfunction is due to underlying causes. Treating those conditions may help resolve the problem without ED medications. In other cases, performance anxiety may be the cause of erectile dysfunction. Addressing the mental and emotional aspects of sexual stimulation may also help. Your healthcare provider can help you navigate the different ED causes and the risks and benefits of various treatment options. 

If you already take Viagra, seek medical advice from your healthcare provider if you feel that the medicine is not working for you.

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Current version

January 18, 2024

Written by

Linnea Zielinski

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.