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Cialis vs. Viagra: What’s the Difference?

Kristin Hall, FNP

Medically reviewed by Kristin Hall, FNP

Written by Our Editorial Team

Last updated 7/29/2022

Used by millions of men in the United States alone, PDE5 inhibitors such as tadalafil (the active ingredient in Cialis®) and sildenafil (the active ingredient in Viagra®) are two of the most widely used drugs for treating erectile dysfunction (ED), and for good reason.

Cialis and Viagra both work in very similar ways and have similar effects on your erections and sexual performance. But when it comes to effectiveness, convenience, safety and affordability between Cialis and Viagra, which contender wins out?

The truth is that although Cialis and Viagra are similar, there are a few key differences between these two medications that may make one medication a better choice for you than the other. 

Below, we’ve compared Cialis and Viagra on several criteria, from their effectiveness as options for treating ED to their duration of action, ability to be taken with food, potential side effects and more. 

We’ve also shared a few things that you should know about taking Cialis or Viagra before using either medication to treat ED, including potential drug interactions.

What is Viagra?

Viagra is a brand name medication for treating erectile dysfunction, or ED. It contains the active ingredient sildenafil and was developed by Pfizer throughout the 1980s and early 90s, originally as a treatment for angina (a type of chest pain caused by certain heart conditions).

During testing for sildenafil, researchers discovered that many of the participants in their clinical trials reported erections as a side effect.

Viagra was approved by the FDA in 1998, making it the first prescription medication for treating erectile dysfunction. It’s now widely sold as brand name Viagra and as a generic medication as sildenafil.

Both Viagra and generic sildenafil are available as oral medications, meaning tablets you take in advance of sex. It takes about 30 to 60 minutes for a normal dose of Viagra to start working and provide relief from erectile dysfunction.

What is Cialis?

Cialis is also a brand name, prescription medication that’s approved by the FDA for treating ED, or erectile dysfunction. It contains the active ingredient tadalafil and was originally developed by Lilly ICOS, a company now owned by Eli Lilly and Company.

Tadalafil, the active ingredient in Cialis, gained approval from the FDA in 2003. Today, tadalafil is available in brand name form as Cialis and as a generic medication. Like sildenafil, it comes as an oral tablet for use before sex. 

How Cialis and Viagra Work

To understand how Cialis and Viagra work as ED medications, it’s important to quickly go over the basics of how you get an erection in the first place.

Erections start with stimulation, either sensory (when someone touches you, or you hear or see something sexually arousing) or mental (when you visualize a sexual moment). When you start to become sexually aroused, your nervous system stimulates your penis.

As nerve impulses from your brain and the nerves around your penis start to have an effect, the blood vessels that supply your penis dilate, allowing more blood to flow into your penis.

This blood flows into a pair of sponge-like, elongated areas of erectile tissue called the corpora cavernosa, which run along the length of your penis. As blood flows in, this tissue expands and becomes firmer, creating a penile erection. 

As your penis increases in length and firmness, a fibrous membrane called the tunica albuginea contracts, preventing blood from escaping the tissue while you have sex.

After you reach orgasm and ejaculate, the same process occurs, but in reverse, with the fibrous tissue relaxing and blood exiting your penis via outward-flowing blood vessels.

So, how do ED medications like Cialis, Viagra and others fit into this process, and how can they make it easier to get an erection?

Cialis and Viagra, as well as their generic equivalents, belong to a class of drugs referred to as PDE5 inhibitors. These medications work by inhibiting the actions of an internal enzyme called phosphodiesterase type 5 (or PDE5, for short).

PDE5 is present inside the smooth muscle cells of certain blood vessels, including the vessels that supply blood to your penis. Through a complex mechanism, PDE5 works to regulate the flow of blood to your penis and other areas of your body with blood vessels containing PDE5.

By inhibiting the actions of PDE5, medications like Cialis and Viagra increase the total amount of blood that can flow to your penis when you’re sexually aroused.

This increase in blood flow can make it easier for you to get an erection when you feel ready to have sex and maintain it during sexual intercourse.

Now, it’s important to understand that the effects of Cialis, Viagra and similar medications solely target your vascular system -- that is, the vessels that transport blood throughout your body and to your penis. 

They aren’t “sex pills,” and they won’t make you feel sexually aroused on their own, nor will they have an effect on the hormones that give you sexual desire.

However, because medications like Cialis and Viagra can make it easier to get and maintain an erection (and in turn, improve your sexual performance), they can make it easier to get and stay hard when you’re already sexually aroused.

Because both drugs work by affecting the blood vessels that supply your penis, it’s important to be careful before using them if you have a cardiovascular issue, such as high blood pressure, a history of heart disease or if you’ve previously had a heart attack.

We’ve discussed these issues -- as well as the steps that you can take to use Cialis or Viagra as safely as possible -- further down the page. 

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Does Cialis or Viagra Last Longer?

Although Cialis and Viagra work very similarly to improve blood flow to your penis and treat ED, there’s a huge difference in terms of the amount of time that each medication remains active in your body.

Cialis is a long-lasting erectile dysfunction medication. In fact, it’s sometimes referred to as the “weekend pill” for treating ED because it can last for so long.

On average, a normal dose of Cialis or generic tadalafil will offer relief from erectile dysfunction for approximately 36 hours.

This long-lasting effect makes Cialis or generic tadalafil an excellent choice if you’re affected by erectile dysfunction, but don’t know exactly what time of day you’re going to have sexual activity with your partner.

Whether you’re going away for a weekend or just want to be prepared for a more spontaneous sexual encounter without needing to plan out taking oral drugs for ED ahead of time, a dose of Cialis is usually more than enough.

Viagra, on the other hand, is a shorter-acting medication for erectile dysfunction. On average, a normal dose of Viagra or generic sildenafil will provide relief from erectile dysfunction for around four hours. 

This means that Viagra can be a great choice if you need short-term relief from ED, such as for a single night. For example, if you need a sexual confidence boost after a date, taking a Viagra or generic sildenafil tablet can let you focus on enjoying yourself without worrying about ED.

People’s needs from ED medication can differ dramatically, so it’s best to talk to your healthcare provider before deciding that a specific medication is going to be best for you based on the time it’s active within your body. 

It’s also important to keep in mind that Cialis and Viagra don’t always last for precisely 36 or four hours per dose. You may notice the effects of either medication fading sooner or later based on factors such as your body weight, eating habits and certain medical conditions. 

However, in general, Cialis is longer lasting and a better choice for weekends that could involve multiple sexual encounters, whereas Viagra is usually a better choice if you need to treat sexual dysfunction like ED for a single evening. 

Related Post: Is Viagra Over The Counter?

Which Medication Works Faster?

Cialis and Viagra are both fast-acting medications that should produce noticeable improvements in your erections and sexual function within one hour.

On average, it takes around 30 minutes for Cialis to start working. In some cases, you may not notice the full effects of Cialis on your erections and general sexual peformance for one to two hours after taking the medication.

Similarly, Viagra typically starts to work within 30 minutes, although it may take about one hour for the effects of the medication to become fully apparent.

Regardless of whether you use Cialis or Viagra, a few simple techniques can help you to make sure that your medication works in time for you to have sex:

  • Aim to take your medication about an hour before sex. This way, the medication will be completely active (or close to completely active) by the time you and your partner begin sexual activity.

  • Take note of how long it takes before you “feel” the effects of your medication. You may notice that it takes a certain amount of time before you can notice improvements in your erections. This knowledge can help you to “tailor” your future use of ED medication.

  • Avoid eating too much food before using ED medication. Some ED medications, such as Viagra, may take longer to work if taken with a large meal. We’ve discussed the effects of high-fat meals on ED medication in more detail below. 


In general, both medications take a similar amount of time to start working and should be taken 30 to 60 minutes before sex for optimal results.

Which Medication is More Effective: Cialis or Viagra?

Cialis and Viagra are both highly effective as treatments for ED. Both medications have passed through comprehensive, large-scale clinical trials as part of the FDA approval process, with the research showing that both medications work well at producing improved erections.

For example, in an article published in the journal Clinical Interventions in Aging, experts looked at the existing efficacy data for tadalafil (the active ingredient in Cialis) to judge its effectiveness as a treatment for erectile dysfunction.

They found that 88 percent of men with erectile dysfunction reported successful erections after taking Cialis, versus approximately 64 percent of men who used a non-therapeutic placebo.

They also found that the men who used Cialis reported higher levels of sexual satisfaction, as well as more successful attempts at sexual intercourse.

A meta-analysis of clinical trial reports for sildenafil (the active ingredient in Viagra) also found that it was an effective drug for improving erectile function in men with ED.

The meta-analysis, which was published in the journal BMC Urology, noted that 82 percent of men with erectile dysfunction reported improved erections after using sildenafil at a dosage of 100mg prior to sex.

The men who used sildenafil were also more able to successfully have penetrative sex with their partners, suggesting that sildenafil produced improvements in sexual satisfaction. 

When it comes to medication, It’s easy to get obsessed with numbers and assume that because one medication shows an improvement in a slightly larger number of men, it must be the best of the two options. 

However, the reality is that Cialis and Viagra are both extremely effective treatments for erectile dysfunction, and that the tiny differences in effectiveness shown in some studies are just that -- tiny differences. 

Put simply, if you have erectile dysfunction and want a reliable drug that can enhance blood flow and give you reliable, prolonged erections, Cialis and Viagra are both good options.

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Are Cialis or Viagra Affected by Food?

Like other oral medications, CIalis and Viagra are broken down by your stomach acids, allowing them to pass through your liver and into your bloodstream.

Because oral medications need to pass through your digestive tract, the other foods and drinks you consume at the same time as certain medications can have an impact on the rate at which they’re absorbed and able to become effective. 

Your body’s ability to absorb Cialis isn’t affected by food, meaning you can take your daily dose of Cialis without having to worry about your diet slowing down the medication’s effects.

Put simply, Cialis should always start working in 30 minutes to one hour, even if you take it with a large meal.

Viagra, on the other hand, is more affected by food. According to the FDA label for Viagra, while it’s okay to take Viagra with food, using Viagra after a high-fat meal (for example, fried food or a cheeseburger) may increase the amount of time that’s required for the medication to work. 

For best results, you should take Viagra or generic sildenafil on a relatively empty stomach one hour before having sex. 

If you plan to eat before using Viagra (for example, you take it at dinner while out on a date), try to avoid eating foods that are high in fat, which may slow down your body’s ability to absorb the medication and reduce its efficacy.

Overall, because Cialis isn’t affected by food, it’s usually a better option if you need to eat before using your ED medication. 

Cialis Side Effects vs. Viagra Side Effects

When taken as prescribed under the supervision of a healthcare professional, Cialis and Viagra are both safe and effective medications for most men. 

However, like all medications, Cialis and Viagra can both potentially cause adverse effects. Most of these are mild side effects that improve over time, although some side effects related to Cialis or Viagra may be more severe and/or persistent.

Because Cialis and Viagra work in similar ways within your body, they usually cause similar side effects. 

Common side effects of Cialis include:

  • Headache

  • Dyspepsia (indigestion)

  • Nasopharyngitis (nasal inflammation)

  • Back pain

  • Upper respiratory tract infection

  • Facial flushing

  • Myalgia (muscle pain)

  • Cough

  • Diarrhea

  • Nasal congestion

  • Pain in extremities

  • Urinary tract infection

  • Abdominal discomfort

  • Gastroesophageal reflux disease

Most side effects from Cialis are mild and generally uncommon. Headache, the most frequently reported side effect of Cialis, was only reported by 15 percent of users at the highest commonly prescribed dosage (Cialis 20mg), compared to five percent of men who used a placebo. 

Common side effects of Viagra include:

  • Headache

  • Facial flushing

  • Dyspepsia (indigestion)

  • Abnormal vision (blurred vision or changes in color vision)

  • Nasal congestion

  • Back pain

  • Myalgia (muscle aches)

  • Nausea

  • Dizziness

  • Skin rash

In rare cases, Cialis and Viagra may cause more serious side effects, including temporary loss of vision, vomiting, sudden loss of hearing or change in hearing sensitivity and allergic reaction symptoms.

These issues are uncommon, and a causal relationship between Cialis, Viagra and these issues is uncertain.

Our full guide to Viagra (sildenafil) side effects goes into more detail about the potential adverse effects of medications for erectile dysfunction.

In very rare cases, Cialis and Viagra can also both cause priapism (an erection that lasts for four hours or longer). Priapism is a prolonged, painful erection that requires immediate care from a medical professional.

Contact your healthcare provider as soon as possible if you develop a painful or very persistent erection after using Viagra, Cialis or any other type of prescription medicine for ED. 

Most of the time, any side effects from Cialis or Viagra will gradually fade away and stop as the medication leaves your body.

However, because Cialis stays in your body for longer than Viagra, you may notice certain side effects from Cialis for longer. If you’re prone to side effects from PDE5 inhibitors, Viagra may be a better choice for you.

You can also reduce your chances of experiencing side effects of Cialis and Viagra by taking a lower dose of the medication. Research generally shows that side effects from ED medications tend to become less common with dosage reductions.

Overall, Cialis and Viagra have nearly identical side effects -- something that isn’t a surprise, as both medications are very similar. However, because of the longer half-life of Cialis, its adverse effects may persist for longer.

Our guide to what you can expect from erectile dysfunction medication goes into greater detail about the potential side effects of Cialis, Viagra and similar medications. 

Cialis or Viagra: Which Medication is Safer?

Cialis and Viagra both have excellent safety records. However, like all prescription drugs, they can potentially interact with other medications, supplements and recreational drugs.

Cialis, Viagra and other PDE5 inhibitors can become unsafe when used with some high blood pressure medications, as well as medications used to treat heart failure or after some types of heart surgery.

More specifically, when Cialis, Viagra and similar medications are used with nitrites or nitrates, they may cause a sudden drop in blood pressure. This decrease in blood pressure may lead to dizziness, fainting and, in some cases, cause life-threatening issues.

Other cardiovascular medications that may interact with Cialis, Viagra and similar medications for the treatment of erectile dysfunction include alpha blockers and other antihypertensives. 

Some recreational drugs, such as “poppers,” can also interact with Cialis, Viagra and other ED medications. These drugs often contain ingredients such as amyl nitrate and/or butyl nitrate.

Certain medications may increase or decrease the total amount of Cialis or Viagra that’s active in your body at any one time. This may affect your risk of side effects or make your medication less effective at treating ED.

To reduce your risk of developing drug interactions, make sure to tell your healthcare provider about all medications, herbal supplements and/or recreational drugs you currently use or have used recently before using Cialis or Viagra.

In addition to paying attention to potential drug interactions, it’s important to take some simple steps to keep yourself safe while using Cialis or Viagra:

  • Limit your alcohol intake. Although it’s okay to drink a small amount of alcohol with ED medications, drinking lots of alcohol with Viagra or Cialis isn’t recommended. Try to limit your alcohol consumption on the days you plan to use ED medication.

  • Some grapefruit products may interact with Viagra and Cialis. Although this type of interaction hasn’t been specifically studied, research suggests that grapefruit juice may increase exposure to Cialis or Viagra due to its effects on certain liver enzymes.

  • If you have heart disease or an irregular heartbeat, talk to your healthcare provider before using any ED medication. Cialis and Viagra are usually safe, but you may need to take extra precautions if you have an existing heart condition. 

Overall, Cialis and Viagra are both safe, effective drugs. As with all prescription medicine, you’ll need to talk to your healthcare provider about your ED symptoms and general wellbeing before using either type of medication to treat erectile dysfunction.

Cialis and Viagra Dosages

Although Cialis and Viagra have similar effects in your body, the two medications are effective at different doses.

Cialis comes in four different dosages:

  • Cialis 10mg. This is the recommended starting dose of Cialis. Your healthcare provider may prescribe Cialis at this dose if it’s your first time using ED medication. Most of the time, younger men with ED experience good results from a 10mg Cialis dosage.

  • Cialis 20mg. This is the highest recommended dose of Cialis. If you don’t respond to the 10mg dose of Cialis, or you find it doesn’t provide a significant improvement, taking Cialis at a dosage of 20mg may improve your results.

  • 2.5 and 5mg. These dosages of Cialis are intended for daily use. Referred to as “Cialis Daily,” these lower-dose tablets of Cialis are designed for those with ED who would like to have spontaneous sex without having to plan their medication in advance.

Viagra comes in three different dosages:

  • Viagra 50mg. This is the recommended initial dose of Viagra. Your healthcare provider may prescribe Viagra at this dosage if you’re young, if you only have mild to moderate ED, and if you haven’t previously used Viagra or any other ED medications.

  • Viagra 100mg. This is the maximum dose of Viagra. This dose is usually prescribed if you have moderate to severe erectile dysfunction and don’t experience enough of an improvement from the 50mg tablet.

  • Viagra 25mg. This is the lowest available dose of Viagra. Many younger men and men with mild ED notice an improvement from this dose of Viagra. This reduced dose is also less likely to cause side effects.

The specific Cialis or Viagra dose you use can have a real impact on your results from this type of medication, both in terms of its efficacy as a treatment for erectile dysfunction and in terms of your risk of side effects.

If you feel like your dose of Cialis or Viagra isn’t right for you, make sure to tell your healthcare provider as soon as you can.

Which ED Medication Costs More?

The price of Cialis and Viagra can vary based on several factors, including whether you choose brand name medications or generics and where you purchase your medication.

Like with many other types of medication, generic versions of Cialis (which contains the active ingredient tadalafil) and Viagra (which contains sildenafil) are far more affordable than branded equivalents.

For example, we provide generic daily-use tadalafil for $82 per month, or brand name Cialis for $958 per month. 

We also offer generic sildenafil from $3 per use, with brand name Viagra priced from $139 per use.

Brand name and generic medications contain the same active ingredients, meaning they have the same effects in your body. Our full guides to Cialis pricing and Viagra pricing provide more information about the costs of ED medications. 

Is Cialis or Viagra Better?

There’s no “best” drug when it comes to treating erectile dysfunction. Cialis and Viagra produce very similar effects, yet each drug has its own advantages:

  • If you need a “weekend” erectile dysfunction drug that lasts for a long time and lets you have sex whenever you need without having to plan ahead of time, you’ll probably find Cialis a more appropriate choice for you.

  • If you prefer a shorter-acting erectile dysfunction drug that lets you have sex for a single evening without staying in your system too long, you’ll probably prefer the short duration of action and convenience of Viagra.

Although Cialis and Viagra are the two best known ED medications, they’re not the only options available. Other medications for ED include Levitra® (which contains vardenafil) and Stendra®, a newer-generation ED medication that’s faster acting and less likely to cause side effects.

Our guide to the most common erectile dysfunction treatments and drugs goes into more detail about how these medications work, as well as how they compare to each other.

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Get Help With Erectile Dysfunction Online

Erectile dysfunction is a common issue that affects tens of millions of all ages, backgrounds and physical fitness levels in the United States alone.

If you’re struggling with ED, help is available. We offer a diverse range of ED treatments online following a private consultation with a healthcare provider, including FDA-approved medications such as sildenafil, tadalafil and Stendra

You can also learn more about the factors that contribute to ED in our guide to what causes ED and the steps that you can take to treat it

9 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. Ghofrani, H.A., Osterloh, I.H. & Grimminger, F. (2006). Sildenafil: from angina to erectile dysfunction to pulmonary hypertension and beyond. Nature Public Health Emergency Collection. 5 (8), 689-702. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7097805/
  2. Smith, B.P. & Babos, M. (2022, May 3). Sildenafil. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK558978/
  3. Cialis (tadalafil) Tablets. (2004, March 8). Retrieved from https://www.accessdata.fda.gov/drugsatfda_docs/nda/2003/21-368_cialis.cfm
  4. Erection Ejaculation: How It Occurs. (2020, November 27). Retrieved from https://my.clevelandclinic.org/health/articles/10036-erection-ejaculation-how-it-occurs
  5. Dhaliwal, A. & Gupta, M. (2022, April 19). PDE5 Inhibitors. StatPearls. Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK549843/
  6. CIALIS- tadalafil tablet, film coated. (2022, April). Retrieved from https://www.accessdata.fda.gov/spl/data/05dbd8b6-1b9d-436a-a67c-8a16713f753f/05dbd8b6-1b9d-436a-a67c-8a16713f753f.xml
  7. VIAGRA- sildenafil citrate tablet, film coated. (2017, December). Retrieved from https://www.accessdata.fda.gov/spl/data/40578e70-350a-4940-9630-55d90989c146/40578e70-350a-4940-9630-55d90989c146.xml
  8. Frajese, G.V., Pozzi, F. & Frajese, G. (2006, December). Tadalafil in the treatment of erectile dysfunction; an overview of the clinical evidence. Clinical Interventions in Aging. 1 (4), 439-449. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699638/
  9. Moore, R.A., Edwards, J.E. & McQuay, H.J. (2002). Sildenafil (Viagra) for male erectile dysfunction: a meta-analysis of clinical trial reports. BMC Urology. 2, 6. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC115867/

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.