A Complete Guide To Viagra (Sildenafil) Side Effects

A Complete Guide To Viagra (Sildenafil) Side Effects
20 May, 2019

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, Viagra (or, in its generic form, sildenafil) is the most well known and widely used.  

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, it’s a safe, proven and effective medication.

However, like almost all medications, Viagra does have the potential to cause side effects. Most of these 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, the active ingredient in Viagra. We’ve also looked at the data behind many of these 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 are by far the most common side effect of Viagra, affecting about 25 percent of men who use this medication. 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) 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 stretching nerves in the side of your head.

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.

Muscle Aches

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 muscle aches after using Viagra, make sure to discuss this with your doctor. Your doctor 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.

Studies of sildenafil citrate and nasal obstruction show 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.


Some men report feeling dizzy after using ED medication such as Viagra. This is typically due to the increase in nitric oxide Viagra can trigger. 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 doctor 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, 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 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 doctor. It’s also important to avoid drinking alcohol after using Viagra, as alcohol can further relax the LES and worsen heartburn symptoms.


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, 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 doctor about using a lower dose of the medication.

Visual Disturbances

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

Studies state that 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.

Reduced Blood Pressure

Viagra is a vasodilator that can affect your blood pressure. 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 have a more significant effect on your blood pressure and general health. It’s important to discuss this with your doctor before considering Viagra, especially if you use medication to treat a cardiovascular health issue.

Less Common, More Serious Side Effects of Viagra

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.


Priapism is a serious condition in which you experience a painful, persistent erection that lasts for several hours without sexual stimulation. This 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, 200mg at once), as well as men who use sildenafil in combination with penile injection therapy.

In the entire year of 2007, there were only 93 reported cases of this side effect from Viagra and other ED medication. Considering millions of men in the US use Viagra without issue, it’s safe to say that priapism is very uncommon.

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, 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 who were already at risk of vision complications due to a small cup-to-disc ratio that’s associated with this condition.

Hearing Issues

Viagra and other commonly used ED medications are linked to several cases of hearing loss, some of which occurred within 24 hours of using the drugs.

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.  

Although researchers are unsure of why this happens, it’s believed to be linked to the effects of Viagra on the nitrous oxide-cyclic GMP (No/cGMP) pathway. On average, the men affected by this side effect were 56.6 year of age, with 88 percent losing their hearing in only one ear.

Like the vision issues covered above, hearing issues from Viagra are extremely rare. An NHS guide notes that there have only been 47 cases of hearing loss linked to PDE5 inhibitors like Viagra from the introduction of the medications in the late 1990s until 2011, the year the guide was released.

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 medications can cause a sudden drop in blood pressure  that can seriously affect your health.

You should not use Viagra if you also use 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 or Levitra are used in combination with nitrates.

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

Learn More About Viagra and Erectile Dysfunction

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.