If you have erectile dysfunction (ED) your doctor might suggest Viagra (sildenafil) as a treatment option for you.

Viagra is a prescription medication that’s used to treat ED in adult males.*

Viagra comes as a tablet that you take by mouth about an hour before sexual activity. It’s available in three strengths: 25 milligrams (mg), 50 mg, and 100 mg.

For more information about Viagra, see this in-depth article on the drug.

Like other drugs, Viagra can cause mild or serious side effects. Most side effects are mild, but some serious side effects need immediate medical attention. Keep reading to learn more.

* In this article, we use the term “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Some people may experience mild or serious side effects during their Viagra treatment. Examples of Viagra’s more commonly reported side effects include:

  • headache
  • flushing
  • stuffy nose
  • indigestion (upset stomach)
  • mild vision-related side effects*

Other side effects are also possible with Viagra. Read on to learn more.

* To learn more about this side effect, see “Side effects explained” below.

Viagra can cause mild side effects in some people. Examples of mild side effects that have been reported with Viagra include:

  • vision-related side effects*
  • headache*
  • flushing
  • stuffy nose
  • indigestion (upset stomach)
  • dizziness
  • nausea
  • back pain
  • muscle aches
  • skin rash

* To learn more about this side effect, see “Side effects explained” below.

In most cases, these side effects should be temporary. Some may be easily managed, too. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist. And do not stop using Viagra unless your doctor recommends it.

Viagra may cause mild side effects other than the ones listed above. See the Viagra patient information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Viagra, visit MedWatch.

In rare cases, Viagra can cause serious side effects. Examples of serious side effects that have been reported with Viagra include:

* To learn more about this side effect, see “Side effects explained” below.

If you develop serious side effects while taking Viagra, call your doctor right away. If the side effects seem life threatening or if you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Find out the answers to some frequently asked questions about Viagra’s side effects.

How can I manage side effects from Viagra?

Most side effects from Viagra are mild and easily managed. Here are a few tips for managing some of them:

  • Flushing. To cool down a hot flush, you could open a window, turn on a fan, or have a cold drink. It can also help to lie down and rest. It you have flushing with Viagra, drinking alcohol can make this worse.
  • Indigestion. If Viagra upsets your stomach, it can help to take it with food. But it’s important to note that this might mean the drug takes longer to work. Over-the-counter antacids may help relieve indigestion. You can ask your pharmacist to recommend a suitable product.
  • Dizziness. If you feel dizzy after taking Viagra, this can usually be eased by lying down and resting. Then, get up slowly when the dizziness passes. Drinking plenty of fluids may also help. If you feel dizzy with Viagra, drinking alcohol and smoking can make this side effect worse.
  • Back or muscle pain. If you have body aches after taking Viagra, resting or gentle massage may help. If the pain is troublesome, try an over-the-counter pain reliever. You can ask your pharmacist to recommend a suitable product.

To learn how to manage some other side effects of Viagra, such as headache or vision-related side effects, see “Side effects explained” below.

If you have side effects that you can’t easily manage, talk with your doctor. They may recommend taking a lower dose of Viagra. Or they may suggest trying a different treatment for your condition.

Note that some rare side effects of Viagra need emergency medical attention and should not be managed at home. See your doctor as soon as possible if you have:

  • chest pain, dizziness, or nausea while you’re having sex (if these side effects do not get better when you stop and rest)
  • an erection that does not go away and lasts more than 4 hours
  • sudden decrease in hearing or loss of hearing
  • sudden decrease in vision or loss of vision in one or both eyes

In addition to side effects I might have from taking Viagra, can the drug cause any side effects in my partner?

No, taking Viagra isn’t known to cause any side effects in your sexual partner. It could only cause side effects in your partner if the drug got into your semen. But Viagra doesn’t pass into semen in significant amounts.

However, if your partner takes Viagra themselves, they may experience the possible side effects of Viagra discussed in this article. Your partner should not take Viagra that’s been prescribed for you, because it may not be safe for them.

How do the side effects of Cialis compare with those of Viagra?

Cialis (tadalafil) is another drug that’s used to treat erectile dysfunction. It’s in the same class of drugs as Viagra, which means it works in a similar way.

Cialis and Viagra can cause the same serious side effects. These include:

The mild side effects of both drugs are also very similar, but there are a few differences. For example, Viagra can cause changes to your vision (such as blurred vision or increased sensitivity to light), but Cialis doesn’t cause vision-related side effects. On the other hand, Cialis can sometimes cause cough or diarrhea, which have not been reported with Viagra.

It’s important to note that the effects of Cialis last longer than Viagra’s. So any side effects you experience with Cialis may last longer than side effects you experience with Viagra.

If you’d like to know more about how Viagra and Cialis compare, talk with your doctor.

Will the 100-mg dose of Viagra cause more side effects than the 50-mg dose?

It might. Higher doses of most medications tend to cause more side effects than lower doses. But other factors can also affect your risk for side effects. For example, having other medical conditions or taking other medications with Viagra could raise your risk for certain side effects more than taking a higher dose.

In studies of Viagra, some side effects were more common with a 100-mg dose than with a 50-mg dose. These include headache, indigestion, vision changes, and stuffy nose. However, other side effects occurred at similar rates with different doses. So it’s not known if a 100-mg dose is more likely to cause more side effects than a 50-mg dose.

If you’re concerned about the risk for side effects with higher doses of Viagra, talk with your doctor.

What happens if I take too much Viagra?

Taking too much Viagra raises your risk for experiencing side effects from the drug. And any side effects you do have are more likely to be more severe.

Do not take more Viagra than your doctor has prescribed. If the prescribed dose doesn’t work for you, do not take another dose until at least 24 hours later. If you think that Viagra isn’t helping your erectile dysfunction, talk with your doctor. They may recommend trying a different medication.

Most side effects of Viagra are mild and go away quickly as the drug wears off. But in rare cases, some serious side effects can have long-term complications.

For example, Viagra can cause prolonged erection. If not treated, this can lead to permanent erectile dysfunction. Viagra can also cause a serious eye condition called non-arteritic anterior ischemic optic neuropathy, which can lead to permanent vision loss. But these side effects were both rare in studies of the drug.

If you’re concerned about long-term side effects with Viagra, talk with your doctor.

Learn more about some of the side effects Viagra may cause.

Low blood pressure

Viagra can lower your blood pressure after you take a dose. This is temporary and should not cause problems for most people.

However, if your blood pressure falls too low, this could make you feel dizzy or lightheaded. In some cases, it could even cause you to faint. You’re more likely to have these problems with Viagra if you take an alpha blocker, a type of blood pressure drug that’s also used for an enlarged prostate. If you take one of these medications, ask your doctor if Viagra is right for you.

Viagra’s effect on blood pressure can be dangerous for some people. For example, if you take riociguat (Adempas) or nitrate drugs, taking Viagra could cause a sudden large drop in your blood pressure. This could lead to a heart attack or stroke. You should not take Viagra if you take riociguat or nitrate drugs.

Low blood pressure caused by Viagra could also be dangerous if you have a heart condition. Low blood pressure, together with sexual activity, could put too much strain on your heart. If you have a heart condition, talk with your doctor about whether Viagra is safe for you.

What might help

To avoid low blood pressure with Viagra, it may help to drink plenty of non-alcoholic fluids in the hour before you take a dose. This is because being dehydrated could increase your risk for low blood pressure.

If you feel dizzy, lightheaded, or faint after taking Viagra, lie down until you feel better. When you get up, be sure to do so slowly.

If you have these symptoms of low blood pressure after taking Viagra, talk with your doctor before taking another dose. They may recommend taking a lower dose next time.

Vision-related side effects

Viagra can sometimes cause temporary changes to your vision after you take a dose. The most common effect is a blue tinge to your vision. You may also have blurred vision or increased sensitivity to light. These changes to your vision are usually mild and go away quickly. In studies, they were more common with a 100-mg dose of Viagra, but they were uncommon with lower doses.

In rare cases, Viagra can also cause a serious vision-related side effect called non-arteritic anterior ischemic optic neuropathy (NAION). This condition can damage your optic nerve and lead to permanent vision loss.

What might help

If you have changes to your vision after taking Viagra, this should usually improve quickly. It may help to turn off or dim any bright lights.

However, if you have a sudden decrease in vision or loss of vision in one or both eyes, call your doctor right away. Vision loss can be a symptom of NAION.

Headache

Some people may get a headache after taking Viagra. In studies, this was a common side effect of the drug. Most headaches are mild and go away quickly.

What might help

If you have a headache after taking Viagra, it should usually go away on its own. It can help to lie down, rest, and turn off bright lights.

If you have a headache that’s troublesome, you can take an over-the-counter pain reliever, such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). You can ask your pharmacist to recommend a product that’s safe for you.

If you have a severe headache, or a headache that doesn’t go away, talk with your doctor.

Priapism

Like other drugs used for erectile dysfunction, Viagra may cause priapism (long-lasting and sometimes painful erection). But this was a rare side effect in studies of the drug.

Priapism is a medical emergency. If it’s not treated right away, it can damage the tissues in your penis and cause permanent nerve damage and erectile dysfunction.

What might help

If you have an erection that lasts more than 4 hours, you should get emergency medical care. Go to your nearest emergency room, or call 911 or your local emergency number.

Allergic reaction

Like most drugs, Viagra can cause an allergic reaction in some people.

Symptoms can be mild or serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest an over-the-counter oral antihistamine, such as Benadryl (diphenhydramine), or a topical product, such as hydrocortisone cream, to manage your symptoms.

If your doctor confirms you had a mild allergic reaction to Viagra, they’ll decide if you should continue using it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you had a serious allergic reaction to Viagra, they may have you switch to a different treatment.

Keeping track of side effects

During your Viagra treatment, consider keeping notes on any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of drug you were taking when you had the side effect
  • how soon after starting that dose you had the side effect
  • what your symptoms were from the side effect
  • how it affected your daily activities
  • what other medications you were also taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help your doctor learn more about how the drug affects you. And your doctor can use this information to adjust your treatment plan if needed.

Viagra may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Viagra. The list below includes factors to consider.

Allergic reaction. If you’ve had an allergic reaction to Viagra or any of its ingredients, you should not take Viagra. Ask your doctor what other medications are better options for you.

Other medications. If you take Adempas (riociguat) or medications that contain nitrates, you should not take Viagra. Ask your doctor what other medications are better options for you. You should not take nitrate drugs if you’ve taken a dose of Viagra. Doing so could cause a heart attack or stroke. Examples of nitrate drugs include treatments for angina, such as nitroglycerin (Nitromist, Nitro-Dur, Nitrolingual Pumpspray, GoNitro, and others), isosorbide mononitrate (Monoket), isosorbide dinitrate (Isordil), and glyceryl trinitrate. Other nitrate drugs include certain illicit drugs called poppers, such as amyl nitrate.

Heart problems or stroke. If you’ve ever had a stroke or heart problems, Viagra may not be safe for you. Examples of these heart problems include heart failure, angina, heart attack, irregular heartbeat, and aortic valve stenosis. If you’ve ever had these problems, taking Viagra and having sex could put too much strain on your heart. This could cause a heart attack, heart failure, or stroke. Your doctor will determine if it’s safe for you to take Viagra. If you do take it, stop sexual activity if you get any chest pain, dizziness, or nausea. And do not take nitrate medications to treat chest pain (see “Other medications” above). You should call 911 if the symptoms do not go away after resting or if they feel life threatening.

Low blood pressure. If you have low blood pressure, taking Viagra can make your condition worse. This could make you feel dizzy or lightheaded, and it could even make you faint. Talk with your doctor about whether Viagra is right for you. If you do take Viagra, your doctor will prescribe a lower dose for you.

High blood pressure. If you havehigh blood pressure that’s not well managed, Viagra may not be safe for you. Taking Viagra and having sex could put too much strain on your heart. If you have high blood pressure that’s managed with medications, taking Viagra could make your blood pressure fall too low. This could make you feel dizzy or lightheaded, and it could even make you faint. If you have high blood pressure, talk with your doctor about whether Viagra is right for you. If you do take Viagra, your doctor may prescribe a lower dose for you.

Severe kidney problems. If you have certain kidney problems, your body may not be able to get rid of Viagra effectively. This could raise your risk for side effects. If you have severe kidney problems, your doctor may prescribe a lower dose for you.

Liver problems. If you have certain liver problems, Viagra levels could build up in your body. This could raise your risk for side effects. If you have liver problems, your doctor may prescribe a lower dose for you.

Physical problem affecting your penis. If you have certain problems with your penis, such as scarring, bending, or Peyronie’s disease, Viagra may not be safe for you. This is because a rare side effect of Viagra is a prolonged erection. If you already have a physical problem with your penis, this side effect could cause further damage. Talk with your doctor about whether Viagra is right for you.

Blood cell problems. If you have certain conditions that affect your blood cells, such as sickle cell anemia, leukemia, or multiple myeloma, you could be more likely to have a prolonged erection with Viagra. Talk with your doctor about whether Viagra is right for you.

Non-arteritic anterior ischemic optic neuropathy (NAION). NAION is an eye condition that causes a sudden decrease or loss of vision in one or both eyes. In rare cases, Viagra may cause this side effect. You may have a higher risk for NAION with Viagra if you’ve had this condition in the past. If you’ve had NAION, talk with your doctor about whether Viagra is right for you.

Hereditary retinitis pigmentosa. Viagra hasn’t been studied in people with hereditary retinitis pigmentosa (an eye condition that’s passed down in families). If you have this eye condition, talk with your doctor about whether Viagra is safe for you.

Bleeding problems. It’s not known if Viagra is safe for people with bleeding problems. If you have a bleeding problem, talk with your doctor about whether Viagra is right for you.

Peptic ulcer. It’s not known if Viagra is safe for people with an active peptic ulcer. If you have a peptic ulcer, talk with your doctor about whether Viagra is right for you.

Alcohol use and Viagra

It’s best to avoid drinking alcohol with Viagra. This is because combining Viagra with alcohol can make certain side effects of the drug worse. Examples of these side effects include headaches, dizziness, flushing, and blurred vision. Alcohol can also worsen erectile dysfunction, which Viagra is used to treat.

If you drink alcohol, talk with your doctor about how much (if any) is safe for you to drink while taking Viagra.

Pregnancy and breastfeeding while taking Viagra

Viagra is not meant to be used by females.* It’s not known if it’s safe to take Viagra during pregnancy or while breastfeeding.

* In this article, we use the term “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Viagra is an effective treatment for erectile dysfunction. The drug doesn’t cause side effects in most people. However, certain side effects are possible.

If you’re interested in taking Viagra, you may want to know more about whether it will be safe for you. Here are some examples of questions you might want to ask your doctor:

  • Do my other medications increase my risk for side effects with Viagra?
  • Is it safe to take Viagra if I have diabetes?
  • Can taking Viagra cause migraines?
  • Can Viagra cause a heart attack in people who don’t have heart disease?

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.