How Much Sildenafil Should I Be Taking?

Get the lowdown on what the right dose is for you and which lifestyle factors affect how well the ED medicine works.

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Sean Evans


Sean Evans,   

Jan 21, 2020 • 3 min read

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If you’re new to sildenafil, or its name-brand counterpart, Viagra, you may have some questions about your dose amount. There are three different doses of sildenafil: 25mg, 50mg or 100mg, and whether you need the quarter, half or full dose depends on the condition of your erectile dysfunction (ED) and your basic health.

“If you’re a younger guy with no major medical problems and a mild case of ED, I’d start you on a quarter dose of 25mg,” says James Kashanian, M.D., a urologist and assistant professor at Weill Cornell in New York City. “Men with more moderate or severe ED would get the higher or highest dose.” Other medical problems could lead to your doctor prescribing a larger dose, but because sildenafil can affect different parts of your body, including your lungs or heart, it’s vital to adhere to the dose your doctor recommends. 

All the doses take roughly the same amount of time—about an hour post-ingestion—for the medication to be effective, but a larger dose will last longer than smaller ones. A 25mg dose should last for about four hours, but the 100mg dose could take up to four times as long to leave your system.

Keep in mind you may also have to take your prescribed dose of sildenafil a few times before it starts working as optimally as you’d like. “I usually ask my patients to try it four times before I diagnose it as a failure to the medication,” says Dr. Kashanian. If your body is responding but your erections aren’t as strong or lasting for as long as you’d like them to, then you can talk to your doctor about increasing the dose.

Other factors that may play a role in your dose’s efficacy include your age, your diet, pre-existing health conditions, and your mental state. Older men will have a slower metabolism as will those who eat a diet heavy in fatty foods, so the effects of sildenafil may last longer in those patients. Alcohol, however, decreases blood flow to your penis, making the sildenafil less effective. Dr. Kashanian says sildenafil works best on an empty stomach, so don’t plan to take it after a big fancy meal. (Got special dinner plans for Valentine’s Day or an anniversary? Consider hitting the sheets before your reservation, so you can fully enjoy date night.) Diabetes, heart conditions, and other nervous system disorders can also decrease sildenafil’s potency, so discuss these with your physician.

Last, sildenafil requires physical stimulation to be effective, and that means if you’re feeling anxious or nervous, your body may not respond favorably to foreplay. If you’re not relaxed and comfortable during sexual activity, sildenafil may not last as long or be as strong as you were hoping. Bottom line? Make sure you’re in the right headspace before you pop a pill, no matter what dose you’re prescribed.

If you think you might benefit from an ED med or a change in your current prescription, Blink offers online doctor consults for $5. You can get your ED drug prescribed or refilled from the privacy and comfort of home.

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This article is not medical advice. It is intended for general informational purposes and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition. If you think you may have a medical emergency, immediately call your physician or dial 911.

Blink Health is not insurance. The discount prescription drug provider is Blink Health Administration, LLC, 1407 Broadway, Suite 2100, New York, NY 10018, 1 (844) 265-6444,

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