If you experience difficulty getting an erection or maintaining one, you are not alone. About 30 million men in the United States have erectile dysfunction (ED). ED is commonly treated with lifestyle changes, if needed, as well as prescription medication.

Viagra contains the active ingredient sildenafil citrate, or sildenafil. This “little blue pill,” as it is often referred to, is a commonly prescribed medication for ED treatment. Viagra was approved by the U.S. Food and Drug Administration (FDA) in 1998 and is the first member of a class of erectile dysfunction medications called phosphodiesterase-5 (PDE5) inhibitors.

The way Viagra works is by affecting a chemical in the body called nitric oxide, which helps relax blood vessels. This helps increase blood flow to the penis, which makes it easier to get an erection. It's important to note that Viagra will not cause an erection by itself—it must be used in combination with sexual stimulation.

Continue reading to learn more about how long Viagra lasts and what can affect its duration. Note that everything discussed in this article applies to both brand name Viagra and its generic, sildenafil.

How long does Viagra last?

Viagra can work for up to 4 hours, but the effects of this medicine are not as strong after the first two hours. Because the timeline is not exactly the same for everyone, you may need some trial and error to find the optimal time to take Viagra for the best results.

The table below compares Viagra with other PDE5 inhibitors. Remember, not everyone may experience the exact same results in terms of how long Viagra takes to work and how long it lasts. You can talk with your healthcare provider if you have any questions or concerns.

PDE5 inhibitors

How long does Viagra stay in your system? How long is Viagra effective?

Viagra can improve your erections for up to 4 hours. However, this does not mean that at the 4-hour mark, the drug is out of your body. All drugs, including Viagra, must gradually be processed and removed from the body.

A drug’s half-life is the amount of time it takes for about half of a dose of the drug to be removed from the body. It usually takes 4 to 5 half-lives for a medicine to almost completely leave the body. Since the half-life of Viagra is about 4 hours, it can take up to 20 hours, which is 5 half-lives, for a dose to be almost completely removed from the body.

Although there is some medicine remaining in your body for up to 20 hours, that does not mean the drug is effective the entire time. Viagra is generally effective for the first 4 hours, and its effectiveness will gradually decrease over time until it is removed from the body.

Factors that affect how long Viagra lasts

As mentioned above, individual results may vary on how long a dose of Viagra lasts. Factors such as dosage and drug interactions, among others, may play a role in how long Viagra lasts.

Dosage

Viagra is available in both brand and generic forms in the following doses: 25 mg, 50 mg, and 100 mg. The dosage of Viagra may impact how long it lasts. A higher dose may work better and result in longer-lasting effects, but individual responses will vary. Your healthcare provider will tell you what dose of Viagra to take. Do not take more medicine than prescribed, as doing so could increase the risk of side effects.

Age and other health conditions

Age can affect how long Viagra lasts and how well it works. Certain individuals may be more likely to build up higher levels of Viagra in the body, including older adults, and people with kidney or liver problems.

Diet

You can take Viagra with or without food. However, if you take Viagra after eating a meal that is high in fat (such as pizza and ice cream), it may take longer for the medicine to kick in. When Viagra is taken with a high-fat meal, it may take an additional 60 minutes to start working—meaning it could take two hours instead of the usual one hour—and it may not work as well.

In addition to benefiting your overall health, eating a healthy diet in general (not just when you take the medicine) can help with erectile dysfunction.

What's more, incorporating physical activity into your lifestyle can help improve ED, especially if you have obesity, high blood pressure, heart conditions, or metabolic syndrome. Check with your healthcare provider before starting any new exercise program, to make sure any exercises you are planning on doing are safe with your medical conditions.

If you eat grapefruit or drink grapefruit juice, check with your healthcare provider, as grapefruit may cause Viagra levels to increase, which can worsen the side effects of the medicine.

Alcohol

Alcohol does not chemically interact with Viagra. However, generally limiting alcohol to no more than two drinks per day can help with ED. Additionally, it is important to consider serving sizes. One drink is equivalent to 12 ounces of regular beer, 5 ounces of wine, or 1.5 ounces of spirits.

Some research has found that drinking alcohol is associated with risky sexual behaviors, including having sex at a younger age, improper condom use, and multiple sex partners.

Drug interactions

Before taking Viagra, tell your healthcare provider about all the medications you take, including prescription and over-the-counter drugs, vitamins, and dietary supplements.

There are some medications you should never take with Viagra. If you take a nitrate medicine such as isosorbide mononitrate, or nitroglycerin—either occasionally or regularly—it is not safe to take Viagra. Taking a nitrate with Viagra could result in dangerously low blood pressure, which could lead to dizziness, fainting, or even a heart attack or stroke. Also, you should not take Viagra if you take a guanylate cyclase stimulator such as Adempas (riociguat). Adempas is a medicine that is used to treat high blood pressure in the lungs.

Viagra can lower your blood pressure. If you take medicine for high blood pressure, adding Viagra could result in dangerously low blood pressure. Consult your healthcare provider for medical advice.

Viagra also interacts with other medications, some of which can significantly increase Viagra levels in your body. This is why it is important to talk to your doctor about drug interactions and how they may affect you.

Mental health

Erectile dysfunction (ED) can impact a man's mental health, relationships, and overall well-being. Many studies have found that depression can increase the risk of ED, and ED can also lead to depression. Experiencing sexual difficulties can cause anxiety and loss of confidence, which may lead to avoiding sex, among other issues. If you have ED, consulting a mental health professional can be helpful (in addition to prescription medication), allowing you to address both mental and physical factors.

How long does it take for Viagra to work?

Viagra is usually taken about one hour before sexual activity. However, the time it takes for Viagra to work can vary. It can start working in as soon as 30 minutes, or take one hour or even longer to work.

If you take Viagra on an empty stomach, the medicine usually reaches its maximum effect in 30 to 120 minutes, with an average of about 60 minutes. Taking Viagra with a high-fat meal (see “Diet” section above) can cause the medicine to take longer to kick in.

The prescribing information states that Viagra can be taken anywhere from 30 minutes to 4 hours prior to sexual activity. With this wide of a range, it may take some trial and error to determine the best timing for your dose, as individual experiences can vary.

And remember, Viagra only works in combination with sexual stimulation. You will not get an erection simply by taking this medicine.

Does Viagra help with premature ejaculation? Will it help me last longer in bed?

Yes, Viagra may help if premature ejaculation is a problem. Among other benefits, studies have found that Viagra may make you feel like you have more control over your ejaculation. Taking Viagra may also help with a second erection.

Viagra alternatives - how long they last

In addition to Viagra, there are several alternatives available to help with ED. For example, there are other prescription ED medications—such as Cialis (tadalafil), Levitra® (vardenafil), Stendra® (avanafil), and various over-the-counter (OTC) supplements.

How long does Cialis last?

Cialis®, like Viagra, is a prescription drug that is part of the PDE5 inhibitor drug class. However, a dose of Cialis (tadalafil) can last up to 36 hours. Cialis has a half-life of 17.5 hours—compared to Viagra’s half-life of 4 hours.

Because of this long half-life, it can take up to 88 hours (or between 3 and 4 days) for a dose of Cialis to almost completely leave the body, although it may not be effective for that long.

There are two ways to take Cialis—it can be taken as needed before sexual activity, similar to Viagra, or it can be taken as a lower once-daily dose (and does not need to be taken before sexual activity). Your healthcare provider can help determine the best way for you to take Cialis.