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A Complete Guide to Viagra® (Sildenafil) Side Effects

Kristin Hall, FNP

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 2/17/2022

Erectile dysfunction, or ED, is a common condition that affects as much as 40 percent of men by the age of 40. Several medications are available to treat erectile dysfunction. Of these, brand name Viagra® (or, in its generic form, generic Viagra, or sildenafil) is the most well-known and widely used PDE5 inhibitor for erectile dysfunction.  

Viagra works by increasing blood flow to the penis, making it easier for you to get and maintain an erection when you’re sexually aroused. Used by millions of men in the United States alone, it’s a safe, proven and effective medication. Viagra's active ingredient, sildenafil, is approved by the Food and Drug Administration for the treatment of erectile dysfunction and pulmonary arterial hypertension.

However, like almost all medications, Viagra does have the potential to cause side effects. Most of these Viagra side effects are minor and temporary (typically, they fade away as the medication exits your body), although some can become serious if you use other prescription medications.

Below, we’ve listed the common and uncommon side effects of sildenafil. We’ve also looked at the data behind many of these Viagra side effects to explain how and why they happen, as well as what you can do to manage them.

The Most Common Side Effects of Viagra

Viagra has several common side effects. These side effects typically occur at the same time as the medication is active in your body (typically, three to five hours), although some can continue for several hours after Viagra’s active effects wear off.

Headaches

Headaches are one of the most common side effects of Viagra, affecting about 25 percent of men who use this medication, according to the FDA 

The headaches caused by Viagra are usually mild and typically fade away as the drug becomes less concentrated in your bloodstream.

Other ED medications, such as Cialis® (tadalafil or generic Cialis) and Levitra, are also linked to headaches. These drugs all work by widening your blood vessels, which helps to improve blood flow to the erectile tissue in your penis.

This has the side effect of also increasing blood flow to other areas of your body. As your blood vessels increase in diameter, it can contribute to headache pain by increasing blood supply to your head causing some people to have headaches.

As the effects of Viagra fade and your blood vessels constrict, it’s normal for any headaches you experience from the medication to become less intense.

Our guide to treating headaches from ED medication explains what you can do if you often notice a headache after using Viagra. Most of the time, Viagra-induced headaches can be treated either by reducing your dosage of the medication or using over-the-counter pain relief.

Back Pain 

Some Viagra users experience muscle aches after taking the medication. This can range from a mild level of muscular pain to pain in a specific area, such as the lower back. Muscle aches and pain after using Viagra can be treated using over-the-counter pain relief medications.

If you have recurring, uncomfortable back pain or muscle aches after using Viagra, make sure to discuss this with your healthcare provider. Your healthcare provider might recommend a suitable form of pain relief or suggest using a lower dose of Viagra for ED treatment.

Nasal Congestion

Viagra can cause you to get a stuffy, partially blocked nose. Like most other side effects, this is a temporary issue that is most common while the medication is still in your system, although in some cases it can persist for several hours after the main effects of Viagra wear off.

This side effect is the result of Viagra’s effects on blood flow. By causing your blood vessels to widen, Viagra can contribute to nasal obstruction. This makes it more difficult to breathe through your nostrils.

A small study of sildenafil citrate and nasal obstruction published in the Tohoku Journal of Experimental Medicine shows that this side effect can occur at a 50mg dose of Viagra. Like other side effects, it might be possible to limit the effects of Viagra on your ability to breathe through your nose by reducing your dosage of the medication.

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Dizziness

Some men report feeling dizzy after using ED medication such as Viagra. This is typically due to the lowering of blood pressure that Viagra can sometimes cause. Most of the time, any dizziness from Viagra is light and passes quickly as your body gets used to the effects of the medication.

If you frequently experience dizziness after using Viagra, let your healthcare provider know. Like many other common side effects of Viagra, you can often limit or avoid dizziness by adjusting your dosage of the medication.

Facial Flushing

Sildenafil, the active ingredient in Viagra, causes your blood vessels to widen, improving blood flow to your penis and making it easier to get an erection.

This can also cause blood vessels in other parts of your body to widen. When the blood vessels in your skin dilate, your skin can take on a red, flushed appearance. Some men who use Viagra notice this effect around their nose, cheeks and forehead.

Just like headaches, facial flushing fades away on its own as the dose of sildenafil that’s active in your body decreases. If you’re prone to facial flushing from Viagra, using a lower dose of the medication might cause this side effect to become less intense and visible.

Facial flushing is a common side effect of all ED medications, meaning that switching to Cialis or Levitra might not prevent this from occurring.

Indigestion/Heartburn

Indigestion, or heartburn, is a common side effect of Viagra. This occurs because of the effects of Viagra on smooth muscle tissue in your body.

After you take Viagra, the smooth muscle tissue in your penis starts to relax, leading to higher levels of blood flow. This effect also occurs in other smooth muscle tissue, including the lower esophageal sphincter (LES), a group of muscles that separate your stomach and esophagus.

This can result in small quantities of stomach acid making its way from your stomach into your esophagus.

Heartburn from Viagra can be treated using over-the-counter antacids such as Gaviscon, which creates a protective layer on the top of your stomach contents. If you experience mild heartburn or indigestion-related chest pain from Viagra, drinking several glasses of water can also help to prevent discomfort.

If you frequently get indigestion/heartburn after using Viagra, consider discussing switching to a lower dose of the medication with your healthcare provider. It’s also important to avoid drinking alcohol after using Viagra, as alcohol can further relax the LES and worsen heartburn symptoms.

Nausea

Sildenafil, the active ingredient in Viagra, can cause a small percentage of users to experience nausea shortly after it’s taken. Of the common side effects of Viagra, this is one of the rarest — in a four-year study published in the journal, Therapeutics and Clinical Risk Management, only one out of 979 participants reported nausea as a side effect.

Nausea from sildenafil is generally mild. Like other side effects, it most frequently occurs while the medication is active, with nausea and stomach discomfort typically fading away as Viagra’s effects wear off.

If you feel nauseous after using Viagra, consider talking to your healthcare provider about using a lower dose of the medication.

Visual Disturbances

Viagra is linked to several vision changes, including blurred vision, increased brightness of lights and cyanopsia, a form of chromatopsia in which your vision becomes overly blue.

According to a study published in the journal, Progress in Retinal and Eye Research, these effects are transient and mild, with vision issues typically occurring as the sildenafil in Viagra is at its peak concentration in the body. Long-term studies of Viagra do not show any lasting, permanent side effects related to vision or the structure of the eye.

Low Blood Pressure

Viagra is a vasodilator that can affect your blood pressure. The FDA says that on average, people’s blood pressure drops by 8.4/5.5 mmHg after taking a typical dose of Viagra. This reduction is small and doesn’t lead to any negative health effects in people with healthy, non-hypertensive blood pressure.

In short, if you’re healthy and don’t have any blood pressure issues, Viagra will affect your blood pressure, but not in a dangerous way.

If you have cardiovascular disease or hypertension, Viagra could cause a sudden decrease in blood pressure and have a more significant effect on your general health. It’s important to discuss this with your healthcare provider before considering Viagra, especially if you use medication to treat a cardiovascular health issue.

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Less Common, More Serious Viagra Side Effects

Although serious side effects from Viagra are highly uncommon, they can still happen. Viagra has several uncommon side effects, including interactions with certain medicines used to treat hypertension and a small risk of priapism. Along with allergic reactions, these are more serious side effects of viagra to look out for.

Priapism

Priapism is a serious condition in which you experience a persistent, painful erection that lasts for several hours without sexual stimulation. This type of prolonged erection can lead to permanent damage to the erectile tissue of the penis.

Compared to other Viagra side effects, priapism is very rare. Most cases of priapism related to Viagra involve people taking overly large doses of the medication (in one case, according to an article published in The Bulletin of Tokyo Dental College, 200mg at once), as well as men who use sildenafil in combination with penile injection therapy.

If you do experience priapism after using Viagra or any other ED medication, you should seek emergency medical care. Priapism is a serious medical emergency that needs to be treated by a qualified professional in order to avoid damaging your penile tissue.

Damage to the Optic Nerve

Although it’s extremely rare, erectile dysfunction drugs such as Viagra are linked to damage to the optic nerve, or nonarteritic anterior ischemic optic neuropathy, in a very small percentage of users.

Nonarteritic anterior ischemic optic neuropathy can cause loss of vision as a result of insufficient blood supply to the optic nerve. In severe cases, this condition can lead to the loss of the upper or lower hemifield of the visual field (for example, loss of half of one eye’s field of vision).

In a 2006 review of clinical trial data published in the International Journal of Clinical Practice, researchers found that approximately 2.8 cases of NAION (nonarteritic anterior ischemic optic neuropathy) occur per 100,000 patient-years of Viagra use, making this an extremely rare potential side effect.

It’s worth noting that most of the cases of optic nerve damage associated with Viagra reported in the US involved men whowere already at risk of vision complications due to a small cup-to-disc ratio that’s associated with this condition, according to the British Journal of Ophthalmology.

Sudden Loss of Hearing

An extremely small percentage of men who’ve used Viagra have experienced a condition that’s known as sudden sensorineural hearing loss (SSHL). This involves damage to the inner ear that can cause permanent loss of hearing.  

Like the vision issues covered above, hearing issues from Viagra are extremely rare.

Interaction With Blood Pressure Medications

Sildenafil, the active ingredient in Viagra, can interact with some medications used to treat high blood pressure. Used together, these drug interactions can cause a sudden drop in blood pressure that can seriously affect your health.

You should not use Viagra if you also use prescription drugs such as nitrates, such as nitroglycerin, isosorbide dinitrate, isosorbide mononitrate or amyl nitrate, to treat hypertension. Viagra should not be taken with “poppers,” which often contain ingredients such as amyl nitrate.

These drugs have the potential to interact with Viagra to cause a sudden, severe drop in blood pressure that can lead to loss of consciousness or cardiac arrest. In addition to Viagra, these side effects can potentially occur if Cialis, Levitra, or Stendra are used in combination with nitrates.

If you have any cardiovascular health issues, such as hypertension or heart disease, you must seek medical advice from your healthcare provider about these issues and any medication you take for them before discussing the use of Viagra or any other ED medication.

Pre-Existing Medical Conditions & Viagra

Unfortunately, certain medical conditions may increase the likelihood of side effects, especially cardiovascular conditions. There are actually quite a few pre-existing health conditions and contraindications for certain medications with generic sildenafil for Viagra. 

When you do speak to a healthcare professional about it, make sure they know everything — your medical history, your medication history, including over the counter and herbal supplements,  and whether you’ve had any recent health issues, etc. 

But generally speaking, some pre-existing conditions you should look out for are:

  • Heart problems, such as history of heart attack or heart failure, or irregular heartbeat

  • Liver conditions 

  • Kidney conditions

  • Strokes

  • Sickle cell anemia (or other blood cell issues and disorders)

  • Retinal diseases

  • Conditions that affect the shape and size of your penis, like Peyronie’s Disease 

Again, these are just a few of the potential pre-existing health conditions you should disclose to your healthcare provider. Just make sure you’re honest with them about everything, and they’ll be able to help you decide if Viagra is the right treatment for you.

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In Conclusion: Viagra Side Effects

Overall, Viagra is a safe and highly effective medication. It’s used regularly by millions of men in the United States alone, as well as tens of millions worldwide. While some side effects, such as facial flushing and headaches, are common, serious side effects are extremely rare.

12 Sources

Hims & Hers has strict sourcing guidelines to ensure our content is accurate and current. We rely on peer-reviewed studies, academic research institutions, and medical associations. We strive to use primary sources and refrain from using tertiary references.

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  7. Laties, A., & Zrenner, E. (2002, September). Viagra (sildenafil citrate) and ophthalmology. Progress in retinal and eye research. Retrieved January 4, 2022, from https://www.ncbi.nlm.nih.gov/pubmed/12207947
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  9. Pomeranz, H. D. (2006, February). Can erectile dysfunction drug use lead to ischaemic optic neuropathy? The British journal of ophthalmology. Retrieved January 4, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1860153/
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This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.