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How to Take Sildenafil for Erectile Dysfunction

Katelyn Hagerty FNP

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 4/02/2021

Okay, so your healthcare provider wrote you a prescription for Viagra® — now what? We’re glad you asked. Before you’re off to the races, there are a few things about sildenafil that you should know.

In this piece, we’ll be covering how to take sildenafil (generic Viagra) for ED, what you should know before taking it, side effects of sildenafil and more.

How to Take Sildenafil for Erectile Dysfunction

When you filled your prescription, the pharmacist probably gave you a quick rundown of the basics, which probably included a fair amount of confusing medical jargon. We’re here to break it down for you, so you know exactly how to take Viagra for erectile dysfunction.

To start, there are typically three dose strengths of Viagra that healthcare providers will prescribe, based on your needs — 25mg, 50mg and 100mg. For most patients, the recommended dose is 50mg taken as needed, approximately one hour before sexual activity.

Based on the effectiveness and ability to tolerate the drug, your healthcare provider may adjust the dosage up to 100mg or down to 25mg. It is important to note here that the maximum dose per day is 100mg of sildenafil, so don’t take another 100mg if the first isn’t working the way it should. 

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What You Should Know Before Taking Sildenafil

Before popping that little blue pill, there are a few things you should know.

Viagra does not protect you from STIs. Therefore, you should always practice safe sex and wear a condom.

You can take Viagra with or without food. However, a fatty or heavy meal can block the absorption of the active ingredient in Viagra (sildenafil citrate) and can make the drug less effective for your erection. 

If you do plan to eat a meal before taking Viagra, make sure to have it as your breakfast or lunch. That way, it gives your body time to digest the food, making it quick and easier for sildenafil to absorb into the bloodstream.

Grapefruit juice may also impede or delay the absorption of Viagra in the body. Make sure to talk to your healthcare provider about eating grapefruit and drinking grapefruit juice while taking Viagra.

What To Do if You Forget a Dose

Since sildenafil is taken on an as-needed basis, there’s no need to worry about forgetting a daily dose. Simply take the drug approximately one hour before sex and you’ll be good to go.

This does mean, however, that you’ll need to be prepared ahead of time. Sildenafil does not allow for a high degree of sexual spontaneity, so if you expect to have sex within the hour, make sure to take your sildenafil ahead of time for ideal erection timing. Don’t take it too early (more than three to four hours ahead of time), as the effects can wear off and you can lose your erection.

Side Effects of Sildenafil

As with any drug, Viagra does come with its share of side effects. 

Common side effects include headaches, flushing, upset stomach, blurred vision, nasal congestion, muscle and back pain, nausea, dizziness and rash. Most of these common side effects are mild to moderate and will go away as your body adjusts to the drug.

Serious side effects of sildenafil also exist. These side effects include chest pain and sudden vision loss and hearing loss. If you experience any of these serious side effects, seek medical attention right away.

An erection lasting longer than four hours (priapism) is also a serious side effect and is considered a medical emergency. If this happens to you, go to the emergency room right away to prevent permanent blood vessel damage in the penis.

If any of these side effects are affecting your quality of life, it’s worth it to talk to your healthcare provider about possible alternatives to Viagra. Your healthcare provider can adjust your dose or recommend another ED drug for you to try instead.

For more common Viagra warnings and precautions, check out this post.

Who Should Not Take Sildenafil?

Viagra might not be right for some men. If you fall into any of the below categories, it’s best to speak to your healthcare provider about possible alternative ED medicines.

Men who have been advised by their healthcare provider not to participate in sexual activity due to their cardiovascular status (due to arterial hypertension, pulmonary hypertension or heart disease, for example) should not take sildenafil. Sildenafil dilates the vascular system, which can cause a drop in blood pressure and may potentially be life-threatening.

Men who are currently taking medicines such as nitrates, alpha-blockers or antihypertensives for arterial hypertension should speak to their healthcare provider about potential drug interactions. Sildenafil can have a lowering effect on blood pressure when taken in conjunction with these medicines and can be very dangerous.

If you take recreational drugs with amyl nitrate and butyl nitrate (known as “poppers”), you should not take sildenafil. Taking recreational drugs containing nitrates in combination with Viagra can cause your blood pressure to drop dangerously low.

It is also dangerous to take sildenafil tablets at the same time as other ED medicines, such as Cialis®, Levitra® and Stendra®. Taking multiple PDE5 inhibitors at the same time can put you at risk for a dangerous drop in blood pressure.

For more information on the latest ED treatments, click here.

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Sildenafil is a great erectile dysfunction treatment for many men. However, before you take your first dose, there are a few things you should know about the drug, including side effects, who should not take sildenafil and more. If you’re interested in learning more about ED treatment with sildenafil and if it’s right for you, start a conversation with your healthcare provider. 

For more information on erectile dysfunction, check out our other blog posts.

3 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. Highlights of prescribing information: Viagra (sildenafil citrate). (2017, August). Retrieved from
  2. Viagra (sildenafil citrate) tablets. (2007, October). Retrieved from
  3. Sildenafil. (2018, January 15). Retrieved from

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.

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