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How to Take Sildenafil for Erectile Dysfunction

Mike Bohl, MD, MPH, ALM

Reviewed by Mike Bohl, MD

Written by Steph Coelho

Published 04/01/2021

Updated 03/05/2024

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 PDE5 inhibitors, sildenafil is a safe and proven treatment for ED — if used as directed. It’s been FDA-approved since 1998, after all.

PDE5 is short for phosphodiesterase type 5, and it’s an enzyme that’s part of a pathway that impacts blood flow to the penis. PDE5 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.

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 starting dose of sildenafil is 50 milligrams, which you’d take 30 minutes to four hours before sexy time.

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

It’s also possible to be prescribed doses in multiples of 20 mg, including 20 mg, 40 mg, 60 mg and 80 mg. In these cases, the tablets you have would actually be the generic form of Revatio, a medication that has the same active ingredient as Viagra but is FDA approved for a different condition (although it can be prescribed off label for ED).

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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 — at least 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.

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 how the body processes sildenafil. 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)

  • To better address underlying causes of 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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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.

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:

  • 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.

  • Taking medications for high blood pressure. Using sildenafil when you 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, 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 nitrites found in certain recreational drugs popularly known as “poppers,”, causing a dangerous drop in blood pressure.

  • Other PDE5 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 low blood pressure. More of something isn’t always better! 

  • Other drugs. Aside from heart medications and other PDE5 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 supplements, which aren’t regulated in the same way as prescription drugs.

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

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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 at least 30 to 60 minutes and no more than four hours 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 oral 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

  1. Highlights of prescribing information: Viagra (sildenafil citrate). (2017, August). Retrieved from
  2. Dhaliwal A, et al. (2023). PDE-5 inhibitors. Retrieved from
  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
Editorial Standards

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.

Mike Bohl, MD

Dr. Mike Bohl is a licensed physician, a Medical Advisor at Hims & Hers, and the Director of Scientific & Medical Content at a stealth biotech startup, where he is involved in pharmaceutical drug development. Prior to joining Hims & Hers, Dr. Bohl spent several years working in digital health, focusing on patient education. He has also worked in medical journalism for The Dr. Oz Show (receiving recognition for contributions from the National Academy of Television Arts and Sciences when the show won Outstanding Informative Talk Show at the 2016–2017 Daytime Emmy® Awards) and at Sharecare. He is a Medical Expert Board Member at Eat This, Not That! and a Board Member at International Veterinary Outreach.

Dr. Bohl obtained his Bachelor of Arts and Doctor of Medicine from Brown University, his Master of Public Health from Columbia University, and his Master of Liberal Arts in Extension Studies—Journalism from Harvard University. He is currently pursuing a Master of Business Administration and Master of Science in Healthcare Leadership at Cornell University. Dr. Bohl trained in internal medicine with a focus on community health at NYU Langone Health.

Dr. Bohl is Certified in Public Health by the National Board of Public Health Examiners, Medical Writer Certified by the American Medical Writers Association, a certified Editor in the Life Sciences by the Board of Editors in the Life Sciences, a Certified Personal Trainer and Certified Nutrition Coach by the National Academy of Sports Medicine, and a Board Certified Medical Affairs Specialist by the Accreditation Council for Medical Affairs. He has graduate certificates in Digital Storytelling and Marketing Management & Digital Strategy from Harvard Extension School and certificates in Business Law and Corporate Governance from Cornell Law School.

In addition to his written work, Dr. Bohl has experience creating medical segments for radio and producing patient education videos. He has also spent time conducting orthopedic and biomaterial research at Case Western Reserve University and University Hospitals of Cleveland and practicing clinically as a general practitioner on international medical aid projects with Medical Ministry International.

Dr. Bohl lives in Manhattan and enjoys biking, resistance training, sailing, scuba diving, skiing, tennis, and traveling. You can find Dr. Bohl on LinkedIn for more information.


  • Younesi, M., Knapik, D. M., Cumsky, J., Donmez, B. O., He, P., Islam, A., Learn, G., McClellan, P., Bohl, M., Gillespie, R. J., & Akkus, O. (2017). Effects of PDGF-BB delivery from heparinized collagen sutures on the healing of lacerated chicken flexor tendon in vivo. Acta biomaterialia, 63, 200–209.

  • Gebhart, J. J., Weinberg, D. S., Bohl, M. S., & Liu, R. W. (2016). Relationship between pelvic incidence and osteoarthritis of the hip. Bone & joint research, 5(2), 66–72.

  • Gebhart, J. J., Bohl, M. S., Weinberg, D. S., Cooperman, D. R., & Liu, R. W. (2015). Pelvic Incidence and Acetabular Version in Slipped Capital Femoral Epiphysis. Journal of pediatric orthopedics, 35(6), 565–570.

  • Islam, A., Bohl, M. S., Tsai, A. G., Younesi, M., Gillespie, R., & Akkus, O. (2015). Biomechanical evaluation of a novel suturing scheme for grafting load-bearing collagen scaffolds for rotator cuff repair. Clinical biomechanics (Bristol, Avon), 30(7), 669–675.

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