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Is Viagra a Blood Thinner?

Katelyn Hagerty

Reviewed by Katelyn Hagerty, FNP

Written by Nicholas Gibson

Published 09/18/2021

Updated 10/19/2023

Often called “the little blue pill,” Viagra® is commonly prescribed first-line erectile dysfunction (ED) medication for men. The brand-name medication (and the generic version, sildenafil) has been helping millions of men get — and stay — hard during sex since it was approved in 1998 by the U.S. Food and Drug Administration (FDA). 

Viagra’s popularity highlights just how common ED is — the condition affects an estimated 30 million men in the United States alone.

Beyond its effectiveness as an erectile dysfunction treatment, some people wonder if Viagra also works as a blood thinner. Here’s what you should know.

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Interestingly, the discovery of PDE5 inhibitors (the class of drugs Viagra falls into) as a treatment for erectile dysfunction was accidental.

Researchers were actually studying how PDE5 inhibitors could be used to treat heart problems like hypertension (high blood pressure) and related chest pain. When the participants started experiencing surprise erections as a side effect, let’s just say the research took a turn. 

The fact that the originally intended use of Viagra was for cardiovascular health and heart disease prevention might be one reason many people are under the impression that it acts as a blood thinner.

Off-Label Uses for Sildenafil

Even though it’s now a gold standard drug for ED, some off-label uses for sildenafil are related to circulation. Specifically, sildenafil is used off-label for secondary Raynaud phenomenon, female sexual arousal disorder and as an adjunct in the treatment of altitude-induced hypoxemia.

Many drugs have similar off-label uses. This means they’re prescribed for a different purpose than what’s been approved by the U.S. Food and Drug Administration (FDA).

There’s also an important distinction between the uses for generic and brand-name drugs. Under the brand name Viagra, sildenafil (Viagra’s active ingredient) is FDA-approved for erectile dysfunction only.

However, under the brand name Revatio®, sildenafil is FDA-approved for pulmonary hypertension, a serious condition involving high blood pressure in the vessels in the lungs.

This can all get a little confusing, especially when trying to figure out how your ED medication works. So is Viagra a blood thinner or not? How does it affect circulation, anyway?

We’ll answer these questions and dig into the mechanism that makes Viagra the go-to for better sex below.

Blood thinners are medications used to prevent the formation or worsening of blood clots. A blood clot is a mass of blood cells and other substances in your blood that form within your blood vessels.

When you get a cut on your skin or have a damaged vein or artery, a blood clot eventually forms to help control the bleeding. The problem is when a blood clot fails to properly break down when its job is done. 

Blood clots can be dangerous if they detach from your veins or arteries and travel through your body. When this happens, they might end up in your heart or brain and cause a heart attack or stroke. They may even land in your kidneys, lungs or limbs and cause damage to your organs.

Ultimately, blood clots are serious. If they’re not prevented or treated properly, they can be fatal.

Therefore, a blood thinner may be prescribed to someone at a higher risk for stroke or heart attack. This includes those who have risk factors, like an irregular heart rhythm (arrhythmia) or heart or blood vessel disease, as well as folks who previously had a heart attack or stroke.

Types of Blood Thinners

Blood thinners prevent blood clots from forming and help blood flow more smoothly throughout the body. The two main types are:

  • Anticoagulants, which slow the blood clot formation process

  • Antiplatelets, which prevent small blood cells called platelets from forming into clots

The right one to use depends on the person’s condition and health history. The type of blood thinner prescribed will ultimately be determined by a healthcare provider.

Common anticoagulants include warfarin (sold as brand-name Coumadin® and Jantoven®), enoxaparin (Lovenox®) and the injectable medication, heparin.

Common antiplatelets include clopidogrel (Plavix®), ticlopidine (Ticlid®), dipyridamole (Persantine®) and aspirin.

When you’re new to ED drugs, it’s totally normal to have lots of questions, including ones you’d rather ask the internet.

Questions like “Is Cialis® a blood thinner?” and “Does Viagra thin your blood?” are frequently plugged into search engines. Many people also wonder if they should use Viagra to prevent getting ED from a clog in their arteries.

The short answer is no, Viagra is not considered a blood thinner — and neither are other PDE5 inhibitors, like Stendra® (avanafil) or Cialis (tadalafil).

To answer this in more depth, let’s first take a closer look at what Viagra does in your body.

How Viagra Works

Viagra is a PDE5 inhibitor, a category of drugs considered the gold standard in ED treatment. PDE5 inhibitors help with erectile function by way of their vasodilatory effects.

In other words, they help widen the blood vessels and relax vascular smooth muscle, allowing easier blood flow to the penis. They do this by blocking an enzyme called PDE5 from doing its job, which is to relax the penis and soften an erection. 

PDE5 inhibitors are not known to have a significant blood-thinning effect, but it’s understandable that they’d be confused with drugs that do.

Effects on Blood Pressure

Because of Viagra’s vasodilatory effects on the cardiovascular system, it can potentially cause a drop in blood pressure. 

For example, in a 2002 study conducted over two nights, 49 men who either had normal or high blood pressure were given no medication the first night and 100mg of sildenafil the following night.

Participants’ blood pressure and heart rate were monitored, and the authors noted the differences between the two nights. They found that sildenafil resulted in an insignificant reduction in blood pressure among all men in the study. 

According to the Viagra label, higher doses are more likely to cause reduced blood pressure for some users. However, it also says the drop usually isn’t significant enough to cause noticeable symptoms.

Okay, so Viagra isn’t considered a blood thinner — but it can still impact blood pressure. That’s why it’s crucial to tell your healthcare provider your complete medical history and other medications you’re taking prior to using it.

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Erectile dysfunction and health conditions that warrant the use of blood thinners are both very common. This means many men who use ED drugs may also be prescribed anticoagulants.

Before you start using these two types of medication together, make sure your healthcare provider is aware you’re already taking one or the other, as taking Viagra with anticoagulants may increase your risk of bleeding. 

You might also be wondering, Do blood thinners cause ED? Seeing as ED is a multifactorial condition, this is a valid question.

While some cardiovascular conditions can increase your risk of developing ED, there’s no solid evidence that blood thinners themselves cause it. However, there’s a strong correlation between ED and having high blood pressure and high cholesterol. 

It’s worth noting that there have been reports of bleeding among some men who have taken Viagra — but a causal relationship between the two hasn’t been established. 

Still, it’s best to proceed with caution, especially if you’re prescribed a blood thinner due to a heart health issue, such as cardiovascular disease or a congenital heart defect.

Although Viagra itself isn’t harmful to your cardiovascular health, sexual activity can put a strain on your heart.

Always speak with a healthcare professional before combining the two. And don’t be afraid to express any concerns you may have — that’s what your provider is there for.

Whenever you start a new medication, your first step should be to learn about the potential side effects and interactions.

Some possible side effects of Viagra are a bit annoying but not necessarily a big deal. Others should be taken more seriously and warrant speaking with a medical professional right away. In some cases, other treatment options may need to be considered.

Potential Side Effects

Side effects of any drug are unpredictable. Not everyone using Viagra will experience adverse effects, and experiences can be vastly different between two people. Pay attention to anything that feels “off” when using Viagra.

Some of the more common (and typically temporary) side effects of Viagra include:

  • Headaches

  • Nasal congestion

  • Nausea

  • Heartburn

  • Blurred vision

  • Back pain

  • Facial flushing

  • Dizziness

  • Low blood pressure

  • Muscle aches

  • Nose bleeds

  • Trouble falling or staying asleep

These side effects generally occur during the same few hours Viagra is active in your body, though some may continue briefly after the medication wears off. 

Viagra might also result in less common but more serious side effects, like: 

  • Priapism (an erection lasting more than four hours)

  • Sudden hearing loss

  • Vision loss due to damage to the optic nerve

Seek immediate medical attention if you experience any symptom that concerns you. Better safe than sorry, especially when it comes to your body.

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Drug Interactions 

All drugs come with a risk of interactions with over-the-counter (OTC) or prescription drugs, as well as certain supplements. Some of the most critical potential Viagra interactions to be aware of are drugs used to treat cardiovascular conditions. 

Sildenafil shouldn’t be taken with nitrate medications. These drugs are prescribed to treat high blood pressure, congestive heart failure or angina, chest pain relating to reduced blood flow to the heart.

When these drugs are taken at the same time, it can trigger a sudden drop in blood pressure. Not only does this simply not feel good, but it could actually make you pass out. 

The combination may even cause reduced blood flow or severe dilation of your blood vessels. In some cases, this can set you up for a heart attack.

Viagra also shouldn’t be taken with recreational drugs like “poppers.” These often contain substances like amyl nitrate that can interact similarly to the above prescription medication and cause severely low blood pressure.

Existing Medical Conditions

Viagra may be less effective for men with certain health conditions. While discussing other medications you use, make sure your provider is also aware of any existing diagnoses you have.

For instance, sildenafil should be used cautiously by men who have

  • Existing cardiovascular conditions that make them more susceptible or sensitive to changes in blood pressure

  • Bleeding disorders or peptic ulcers

  • A physical deformation of the penis, like Peyronie’s disease (which causes curved, sometimes painful erections due to the formation of scar tissue)

  • A higher risk for priapism (prolonged erection without stimulation)

When in doubt, always check in with your healthcare provider.

Foods to Avoid 

Everyday lifestyle habits, like your diet, also matter when taking Viagra. There are certain foods to avoid with Viagra if you want it to work to its full potential.

Eating a meal high in fat or otherwise heavy (think a cheesy, cream-based pasta dish or a juicy cheeseburger with fries) the day you want to use Viagra can make it less effective. On date night, do yourself (and your partner) a favor and maybe order the dinner salad instead.

Grapefruit juice can also interact with sildenafil, inhibiting its metabolism in your digestive tract. Instead, the sildenafil travels straight into your bloodstream, making it more potent. This can result in flushing, a headache or low blood pressure. 

Finally, while alcohol and sex often go together, it’s best not to double-fist it when taking Viagra. Combining the two increases your risk of experiencing side effects like headaches and flushing, especially when consumed in excess. 

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There’s no way to sugarcoat it: Erectile dysfunction is frustrating for all parties involved. It’s perfectly normal and okay to want to pursue treatment. Just be sure you understand what you’re taking and how to take it properly.

If you’re using Viagra and are concerned about its effects on blood flow, keep the following in mind:

  • It’s not a blood thinner. Viagra and the other PDE5 inhibitors aren’t considered blood thinners. While anticoagulants slow your body’s process of making clots, Viagra works by relaxing muscles in your penis and increasing blood flow to the area.

  • It may cause low blood pressure. Even though sildenafil isn’t a blood-thinning medication, it can trigger a drop in blood pressure. This may not be noticeable for some men, while others might experience severe side effects. This is more likely to happen when Viagra is combined with other drugs, especially blood pressure medication or nitrates. 

  • It’s crucial to use as directed. Not using Viagra as it’s been prescribed to you can create more problems than ED. If you have questions about how to take sildenafil, speak with your healthcare provider or pharmacist. Looking for another option? Consider ED hard mints, chewable erectile dysfunction medication that can be personalized to fit your needs.

Exploring the idea of using erectile dysfunction treatments but haven’t tried anything yet? Take the first step toward improving your sex life with our free ED quiz.

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