Get Hard or Your Money Back. Start here

How Does Viagra Work?

Kristin Hall, FNP

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 8/2/2022

Millions of men use brand name Viagra® every year, making it the single-most popular medication used to treat erectile dysfunction in the country.

Used at the proper dose, Viagra is considered very effective at helping men achieve and maintain an erection and is approved by the Food and Drug Administration for the treatment of ED.

It can help men of all ages affected by ED to get and maintain an erection when aroused, making sexual activity easier and enhancing sexual performance in general.

Although Viagra might seem like an on/off switch for your penis, the way the medication works is fairly complex.

Below, we’ve explained how Viagra works to treat erectile dysfunction.

How Viagra Works

What does Viagra do? Viagra works by inhibiting the enzyme that’s responsible for controlling blood flow out of your penis when you’re sexually aroused. Specifically, Viagra inhibits the phosphodiesterase type 5 (PDE5) enzyme. 

Before we get into this in more detail, it’s important to explain how erectile dysfunction happens and the role PDE5 plays in the process.

Erectile dysfunction, or ED, happens when the PDE5 enzyme stops a sufficient amount of blood from flowing into your corpora cavernosa when you’re aroused. 

For men without erectile dysfunction, PDE5 plays a normal role in making the penis flaccid after sex. However, in men with erectile dysfunction, the actions of PDE5 can make getting erect and staying erect during sex difficult or impossible. 

viagra online

genuine Viagra® makes it possible

ED can range in severity. You could find it difficult to get fully erect when you’re sexually aroused but still get a moderate erection. If your ED is severe, your penis might stay entirely flaccid even when you’re aroused, making penetrative sex impossible.

By inhibiting PDE5, Viagra makes it easier for blood to flow into the blood vessels in your penis, allowing you to get — and stay — hard during sex.

It also reduces the risk of blood flowing back out of your penis during sex, meaning you’re less likely than normal to lose your erection. 

This makes Viagra (as well as similar medications, such as Cialis® and Levitra®, other popular PDE5 inhibitors) a highly effective treatment for erectile dysfunction in most men.

Other erectile dysfunction medications, such as Cialis and Levitra, also work by inhibiting the PDE5 enzyme. These medications differ from Viagra in the amount of time their effects last — Tadalafil (generic Cialis), for example, can provide relief from erectile dysfunction for as long as 36 hours. 

While PDE5 is a major factor in preventing you from getting an erection, it isn’t the only thing that can contribute to erectile dysfunction. You might also find it difficult to get and stay hard if you have:

  • Hormonal issues. Hormonal issues, such as low testosterone, can affect your level of sexual interest. In some cases, this could worsen ED. If your erectile dysfunction is the result of low testosterone or other hormonal issues, Viagra may not be fully effective.
    Our guide to testosterone and erections covers this issue in more detail and lists tactics that you can use to improve your sexual performance.

  • High blood pressure. The medical condition of high blood pressure is one of the most common physical causes of erectile dysfunction. If you have high blood pressure, it can become more difficult for the arteries that supply blood to the penis to properly dilate.
    Our guide to high blood pressure and erectile dysfunction explains this in more detail, with a list of approaches for getting healthier low blood pressure and improving your general health.

  • Heart disease. Certain heart conditions and heart problems (like history of heart attack) can affect the blood supply to your penis and make getting an erection more difficult. For example, atherosclerosis (hardening of the arteries), can reduce blood flow and make medications like Viagra less effective.

  • Psychological causes. Some cases of erectile dysfunction are caused by factors such as depression and anxiety. These factors are unrelated to PDE5, meaning that Viagra and other ED drugs might not be totally effective as treatment options.
    Our guide to the psychological causes of ED dives into this issue in more detail, with a full list of psychological factors that can contribute to and cause erectile dysfunction.

  • Porn consumption. Believe it or not, watching a significant amount of porn could have the potential to contribute to erectile dysfunction. This is called “porn-induced ED” and could be a potential cause of ED in many younger men.
    Our guide to porn-induced ED explains how this occurs in more detail, as well as what you can do to prevent porn from interfering with your ability to get an erection. 

Finally, erectile dysfunction can also occur incidentally if you’re feeling tired, stressed or simply aren’t in the mood for sexual activity. 

Be sure to seek medical advice from a healthcare professional before you take Viagra to discuss any pre-existing health conditions and any over-the-counter or prescription drugs (such as nitrates) you currently are taking that may cause an interaction.

ED treatments, delivered

Generic for Viagra (sildenafil)

The more affordable FDA-approved medication that treats Erectile Dysfunction at a quarter of the cost. 🙌

Generic for Cialis (tadalafil)

Affordable and helps get the job done. Generic Cialis helps you get and maintain your erections through a simple, daily dosage.

Viagra®

The OG Little Blue Pill that made its name as the first prescription Erectile Dysfunction treatment.

Cialis®

Cialis helps you get and keep stronger erections with a daily or as-needed pill.


What Viagra Won’t Do

Sure, Viagra may seem like a magical elixir for your erectile dysfunction, but there are a few things it won’t do, like:

  • Make you last longer in bed

  • Work as the best treatment for premature ejaculation (although you can read more about how it may be able to work for you in our blog)

  • Make your penis bigger

  • Boost your sexual desire or provide you with sexual stimulation

How Long Does it Take for Viagra to Work?

Viagra takes just about an hour to kick in, so, if this is your first time taking the drug, make sure you plan your sexual activities accordingly. If you’d like to learn more about what to expect from this ED drug, like how long Viagra lasts, read our blog.

How to Take Viagra

Be sure to take Viagra one hour (but no more than four hours) before you plan to engage in sexual activity. Also, make sure you are taking the medication on an empty stomach. To learn more about how to take sildenafil citrate (Viagra), read our blog.

Side Effects to Be Aware Of

It is important to be aware of the serious side effects of viagra. These may include:

  • chest pain

  • indigestion

  • loss of vision

Although this list is not limited, be sure to seek medical attention if you start to feel these side effects.

generic viagra (sildenafil) online

get hard or your money back

How Does Viagra Work: Final Thoughts

Sildenafil, the active ingredient in Viagra, or generic Viagra is an effective treatment available for erectile dysfunction. It works quickly and effectively, helping men of all ages enjoy enhanced sexual performance and relief from ED.

Our guide to what you should expect from Viagra and other ED medication lists all you need to know about the experience of using Viagra and other ED drugs, from the medication's average half-life to common side effects, onset of action and more. 

2 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.

  1. DRUGS@FDA: FDA-approved drugs. accessdata.fda.gov. (n.d.). Retrieved June 13, 2022, from https://www.accessdata.fda.gov/scripts/cder/daf/
  2. Erectile dysfunction & heart disease. Cleveland Clinic. (n.d.). Retrieved June 13, 2022, from https://my.clevelandclinic.org/health/diseases/15029-heart-disease--erectile-dysfunction#:~:text=and%20heart%20disease%3F-,There%20is%20a%20very%20strong%20link%20between%20erectile%20dysfunction%20and,at%20one%20point%2C%20had%20ED.

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. Learn more about our editorial standards here.