How to Take Sildenafil for Erectile Dysfunction

Kristin Hall, FNP

Reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Published 04/01/2021

Updated 11/18/2023

Your healthcare provider just prescribed sildenafil (generic Viagra®) for your erectile dysfunction (ED) symptoms. Awesome! We’re glad to hear you’ve got a treatment. 

You’re probably excited to get your mojo back. But it’s also understandable if your head is swimming with questions.

Like other PDE-5 inhibitors, sildenafil is a safe and proven treatment for ED — if used as directed. It’s been FDA-approved since 1998, after all.

PDE is short for phosphodiesterase, an enzyme that relaxes blood vessels and smooth muscles. PDE-5 inhibitors work by inhibiting the action of the enzyme, improving blood flow to your member…and tada — erection!

So, what should you know before taking it? We’ll dig into how to use sildenafil for ED, what to do if you miss a dose and which side effects and interactions to be aware of.

How to Use Sildenafil

Like any medication, following your healthcare provider’s medical advice is crucial. And yet, it’s not always easy to remember complicated dosing guidelines.

Let’s break it down in simple-to-understand terms.

Typical Sildenafil Dosage

Healthcare providers can prescribe sildenafil tablets in different doses. The most common are:

  • 25 milligrams

  • 50 milligrams

  • 100 milligrams

A typical dose of sildenafil is 50 milligrams, which you’d take up to an hour before sexy time.

Your provider may adjust your dosage depending on your needs and how you respond to the medication.

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When to Take Sildenafil

Unlike some other ED meds, you don’t take sildenafil every day. Instead, you’ll pop one as needed before sexual activity — about 30 minutes to an hour before, in most cases. And you shouldn’t take it more than once a day.

Just so you’re aware, the effects typically last up to four hours. So you might want to think twice before changing into those comfy, threadbare sweatpants post-coitus and heading to the grocery store.

What Foods to Avoid Before Taking Sildenafil

Some meds can upset your stomach if you don’t take them with food. That’s not the case with sildenafil. You can take this ED medication with or without food.

Having said that, high-fat meals can impact the absorption of sildenafil and lead to (literally) flimsy results.

Grapefruit juice can also mess with sildenafil absorption. So if you’re a half-grapefruit in the a.m. kinda guy, mention that to your healthcare provider.

What to Do If Sildenafil Doesn’t Work

Your daily dosage should never exceed 100 milligrams — that’s bad-news territory. Not getting results from a 100-milligram dose of sildenafil? Don’t try to take more.

If you’re wondering why sildenafil isn’t helping with your lackluster erections, it might be that you need:

  • A different dose

  • A different ED medication

  • Another kind of treatment altogether (like therapy for psychological ED)

Additionally, taking sildenafil too early (we’re talking more than a few hours before having sex) won’t produce the effects you’re looking for. Your erection is likely to wear off by the time the moment strikes.

Yeah, that means you have to do a bit of sex planning when taking sildenafil. But you might be surprised at how sexy the anticipation can be — for you and your partner. 

Can I Take Expired Sildenafil?

Avoid taking sildenafil if it’s expired. According to the FDA (U.S. Food and Drug Administration), this is why you should skip taking and safely dispose of expired meds:

  • They might be less effective.

  • They might be harboring bacteria (ew).

  • Their chemical composition could be altered, making them unsafe.

How can you tell if meds are expired? Check the label for a date, likely next to the abbreviation “Exp.”

Want more tips on how to get the most out of sildenafil? Read our guide on how to take Viagra for best results.

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What to Do If You Forget to Take Sildenafil

Good news! It doesn’t really matter if you forget to take sildenafil because it’s designed for you to take it as you need it.

But be careful about accidentally doubling up on doses. Missing a dose before sex is no big deal — it might just impact the quality of your erection. However, forgetting you already took sildenafil and taking another dose within 24 hours can lead to complications if you go over 100 milligrams.

More on that below.

Sildenafil Side Effects and Interactions

When taking any new drug, you should be aware of the potential side effects. 

The most common side effects of sildenafil include:

  • Headaches 

  • Flushing

  • Stomach upset

  • Nasal congestion

  • Muscle and back pain

  • Nausea 

  • Rash

  • Dizziness

  • Blurred vision

Most of these mild side effects will go away on their own as your body adapts to taking sildenafil.

But sildenafil also comes with some more rare but potentially serious side effects like:

  • Chest pain (angina)

  • Sudden loss of vision (potentially a sign of non-arteritic anterior ischemic optic neuropathy or NAION)

  • Loss of hearing

  • Allergic reaction 

  • Priapism (an erection lasting longer than four hours)

If you experience any of these symptoms after taking sildenafil, seek immediate medical attention.

And FYI: Even mild side effects can impact your life. If you get an upset stomach every time you take sildenafil, talk with a healthcare professional. They may recommend changing your dose or switching medications altogether. 

Read more about potential sildenafil reactions in our sildenafil side effects guide.

Another thing: Sildenafil isn’t right for everyone. It might be dangerous to use sildenafil if you have certain medical conditions or take certain drugs.

Here’s what to consider:

  • Heart problems. If your healthcare provider told you not to engage in sexual activity because of a heart condition (like a history of heart attack, heart disease, heart failure, angina or arrhythmia, also known as an irregular heartbeat), it’s probably best to abstain from sex and sildenafil.

  • Low blood pressure. Using sildenafil when you have low blood pressure or take medications for high blood pressure or pulmonary arterial hypertension could cause a dangerous, potentially life-threatening dip in blood pressure. Avoid taking sildenafil with nitrates (such as nitroglycerin), alpha-blockers or other blood pressure meds like riociguat.

  • Priapism risk. If you have a condition — like sickle cell anemia, leukemia, Peyronie’s disease or multiple myeloma — that puts you at higher risk of priapism, you should avoid sildenafil.

  • Retinitis pigmentosa. There’s not enough available data to say whether it’s safe for people with this eye disease to take sildenafil.

  • Recreational drug use. Sildenafil can interact with the recreational drugs amyl nitrate and butyl nitrate (popularly known as “poppers”), causing a dangerous drop in blood pressure.

  • Other PDE-5 inhibitors. Don’t mix sildenafil with other ED drugs, like Cialis®, Levitra®, Revatio® (another brand name for sildenafil) or Stendra®. This can put you at risk for severely low blood pressure. More of something isn’t always better! 

  • Other drugs. Aside from heart medications and other PDE-5 inhibitors, taking sildenafil with ritonavir, ketoconazole, itraconazole or clarithromycin (an antibiotic) can increase the concentration of sildenafil in your body and make you more likely to experience side effects.

  • Supplements. Talk with a healthcare professional before mixing sildenafil with over-the-counter (OTC) supplements, which aren’t regulated like prescription drugs.

Learn more about health and drug interactions in our sildenafil interactions guide.

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Understanding How to Take Sildenafil

If you’re living with ED symptoms, you’re not alone. ED affects millions of men worldwide. 

Sildenafil can make it easier to get and keep an erection so you can enjoy a fulfilling sex life.

Here’s what to remember when taking sildenafil for ED:

  • Take it 30 to 60 minutes before sexual stimulation. Also, avoid high-fat foods or meals that can slow absorption.

  • Don’t mix sildenafil with medications that can cause dangerous interactions. Unsure whether your meds are safe to combine with sildenafil? Ask a healthcare professional. 

  • Combine sildenafil with healthy habits. Regular exercise, a balanced diet and quality sleep can maximize your overall health and sexual well-being.

  • There are alternative treatments if it doesn’t work for you. Other erectile dysfunction medications include tadalafil (generic for Cialis), avanafil (Stendra), vardenafil and hard mints chewable ED meds. Your healthcare provider might also recommend adjusting your sildenafil dosage.

Ready to find an erectile dysfunction treatment that works for you? Consult with one of our online providers to learn more about your options.

8 Sources

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  3. Label: Viagra-sildenafil citrate tablet, film coated. (2017, December 15). Retrieved from
  4. Gianmarco Troiano & Giacomo Lazzeri (2021) The potential toxic combination of grapefruit juice and sildenafil, Toxin Reviews, 40:3, 334-337. Retrieved from
  5. Don’t be tempted to use expired medicines. (2021). Retrieved from
  6. Yanoga F, et al. (2018). Sildenafil citrate induced retinal toxicity-electroretinogram, optical coherence tomography, and adaptive optics findings. Retin Cases Brief Rep, 12 (1), S33-S40. Retrieved from
  7. Chamsi-Pasha H. (2001). Sildenafil (viagra) and the heart. Journal of family & community medicine, 8(2), 63–66. Retrieved from
  8. Smith BP, et al. (2023). Sildenafil. Retrieved from
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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. See a mistake? Let us know at [email protected]!

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.

Kristin Hall, FNP
Kristin Hall, FNP

Kristin Hall is a board-certified Family Nurse Practitioner with decades of experience in clinical practice and leadership. 

She has an extensive background in Family Medicine as both a front-line healthcare provider and clinical leader through her work as a primary care provider, retail health clinician and as Principal Investigator with the NIH

Certified through the American Nurses Credentialing Center, she brings her expertise in Family Medicine into your home by helping people improve their health and actively participate in their own healthcare. 

Kristin is a St. Louis native and earned her master’s degree in Nursing from St. Louis University, and is also a member of the American Academy of Nurse Practitioners. You can find Kristin on LinkedIn for more information.

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