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Last updated October 7, 2020. 6 minute read

Sildenafil 100mg: is this the right dose for me?

The highest available dose of sildenafil is 100 mg, but that doesn’t mean it’s the right target dose for you. Sildenafil can have serious side effects, and these side effects are more dangerous at higher doses.

Self Written by Michael Martin
Reviewed by Yael Cooperman, MD

What is sildenafil 100 mg?

Sildenafil is the generic form of Viagra, a.k.a. “the little blue pill,” an oral medication used to treat erectile dysfunction (ED). It’s also sold under the brand name Revatio, which is prescribed to treat pulmonary arterial hypertension (PAH), a condition in which blood pressure in the lungs is higher than it should be (Barnett, 2006).


  • Sildenafil 100 mg (brand name Viagra) is a medication known as a PDE5 inhibitor, commonly used to treat erectile dysfunction (ED).
  • Viagra is available in 25 mg, 50 mg, and 100 mg doses.
  • The maximum daily dosage of Viagra is 100 mg, but that’s not the best dose for everyone.
  • If you’re interested in taking sildenafil for ED, speak to a healthcare provider to find the right dose for you.

Sildenafil is FDA-approved for ED in doses of 25 mg, 50 mg, and 100 mg (DailyMed, 2020). It can also be prescribed “off-label” for ED at 20 mg, 40 mg, 60 mg, 80 mg, and 100 mg. Smaller dosage increments can make it easier for you and your healthcare provider to find an optimal dose.

The highest available dose of sildenafil is 100 mg, but that doesn’t mean it’s the right target dose for you. Sildenafil can have serious side effects, and these side effects are more dangerous at higher doses. 

How long does sildenafil 100 mg last? 

Sildenafil starts working within 30 to 60 minutes. (Some men might find that it works even faster.) You should take sildenafil between 30 minutes and four hours before sexual activity. The medication usually stays in your system for four to five hours.

Sildenafil 100mg price

The price of sildenafil 100mg can vary widely, depending on your insurance coverage, where you live, and where you purchase the medication. According to a popular prescription-discount site, the retail price for ten tablets of sildenafil 100 mg ranges from about $80 to more than $1,000 (GoodRx, 2020).


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What is Viagra used for?

Viagra (sildenafil) is an oral medication for erectile dysfunction (ED). It’s part of a class of drugs called PDE5 inhibitors, which also include tadalafil (brand name Cialis), vardenafil (brand name Levitra), and avanafil (brand name Stendra). 

For ED, sildenafil and other PDE5 inhibitors work by blocking an enzyme called PDE5, which makes blood vessels smaller. During an erection, a natural chemical called cGMP opens up blood vessels in the penis, increasing blood flow there and making the penis harder. Since PDE5 stops cGMP (and blocks erections), inhibiting PDE5 allows cGMP to work its magic and make erections last longer

Keep in mind, though: You don’t automatically get an erection when you take sildenafil or other PDE5 inhibitors; you have to be sexually aroused for them to work.

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What is ED?

Erectile dysfunction (ED) is when you can’t get or keep an erection long enough to have satisfying sex. That can include erections that aren’t as firm or don’t last as long as you’d like.

Experts believe more than 30 million American men have experienced ED at some point (Nunes, 2012). It can happen at any age but becomes more common as men get older. By the time a man is in his 40s, he has about a 40% chance of having experienced ED at some point. That likelihood increases by about 10% for each successive decade of life (Ferrini, 2017).

That said, ED is not considered a “natural” part of aging. It can be caused by a serious health condition, including:

  • Heart disease, which occurs when plaque builds up in the arteries, reducing blood flow to the heart. The same process can restrict blood flow to the penis, leading to ED (Nunes, 2012). 
  • Diabetes, which is characterized by high blood sugar, can damage blood vessels, disrupting proper blood flow (American Diabetes Association, n.d.).
  • Hypertension (high blood pressure) which is when blood pumps through blood vessels too forcefully, damaging, and narrowing those blood vessels (American Diabetes Association, n.d.).  
  • Anxiety and depression, along with issues like relationship problems and performance anxiety, can all cause ED (Rajkumar, 2015).  

That’s why it’s smart to consult a healthcare provider at the first sign of ED. They can assess your overall health and nip any potentially serious issues in the bud.

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There are several other treatments for ED besides oral medications. These include :

  • Medications that are injected into the penis (such as alprostadil, BiMix, TriMix)
  • Lifestyle changes, such as a healthy diet, regular exercise, weight loss, avoiding tobacco, and drinking less alcohol 
  • Surgery to correct conditions that can cause ED, such as Peyronie’s disease
  • Devices that can help blood flow into and stay in the penis, such as cock rings and penis pumps
  • Counseling to improve mental health issues that might be contributing to ED

Considerations in taking sildenafil

Sildenafil can cause low blood pressure, usually within one to two hours after taking it. If you already have low blood pressure, talk with your healthcare provider about whether you should take sildenafil.

You shouldn’t take sildenafil if you are allergic to sildenafil or any of the inactive ingredients in sildenafil.

Don’t take sildenafil if you’re not healthy enough for sexual activity. If you have any questions about whether you’re healthy enough for sex, talk with your healthcare provider.

Sildenafil side effects

Like many medications, sildenafil and other ED medications can cause side effects. Common side effects of sildenafil include headache, facial flushing, nasal congestion, stomach upset, backache, and (rarely) temporary impaired color vision. 

If you have an eye condition called retinitis pigmentosa, check with your healthcare provider before using PDE5 inhibitors like sildenafil. 

Sildenafil can also cause priapism, an erection lasting more than four hours. Seek medical attention immediately if you experience priapism as it can cause irreversible damage if left untreated (DailyMed, 2020). 

Sildenafil drug interactions

Viagra might cause adverse reactions when taken with other medications, including other PDE-5 inhibitor drugs (such as Cialis, Levitra, or Stendra), antibiotics, antifungals, antiretrovirals, nitrates (a medication for high blood pressure or heart disease), or treatments for BPH (benign prostatic hyperplasia).

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Sildenafil and other PDE5 inhibitors should never be taken with nitrates. These include the prescription medications for heart disease and the recreational drug amyl nitrate, also known as “poppers.” Taking sildenafil with nitrates can cause a dangerous (and potentially fatal) drop in blood pressure.

Do not take sildenafil if you take riociguat for pulmonary arterial hypertension.

Buy Viagra

Viagra (sildenafil) is not available over the counter. You need to obtain a prescription for it.

That’s because sildenafil can cause serious side effects, and it shouldn’t be taken by people with certain medical conditions or people taking certain medications.

When buying sildenafil online, beware of counterfeit drugs. Many of the online ads promising Viagra for cents on the dollar are not legit, and the product they sell can be dangerous, containing too little or too much sildenafil, contaminants, and other substances. One study found that up to 77 percent of sildenafil sold online may be counterfeit (Campbell, 2012). When you buy from these sketchy sites, you never really know what you’re getting. 

And when we say you really don’t know what you’re getting, we mean you really don’t know. A few years ago, police in the United Kingdom seized mass quantities of counterfeit Viagra. Laboratory analysis found that the pills contained contaminants like talcum powder, commercial paint, and printer ink (to color the tablets blue) and other medications like acetaminophen and amphetamine. Only 10% of tablets labeled “Viagra 100 mg” were within 10% of the listed strength (Jackson, 2010).  

If you’re interested in taking sildenafil 100mg to resolve ED, the best course of action is to consult a healthcare provider and get a prescription from a reputable source.