Cialis vs. Viagra: What’s the Difference?

Although Cialis and Viagra both make it easier to get and maintain an erection, there are a few key differences between these two ED medications that may make one a better choice than the other for you if you have difficulty getting and staying hard.

The biggest differences between Viagra and Cialis is the total amount of time each medication works — for Cialis, up to 36 hours, and for Viagra, around four hours. But other nuances about how — and when — these medications should be taken will ultimately be very important when deciding which one is right for you.

Is Cialis stronger than Viagra? Is Viagra stronger than Cialis? Which one should you take?

Below, we’ll guide you though these questions and compare Cialis and Viagra on their effectiveness, their duration of action, potential side effects and more. But let’s quickly cover what they have in common, to set the stage.

Used by millions of men in the United States alone, phosphodiesterase type 5 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. 

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’s full role in your vascular system is complicated, but on a simple level, it’s involved in the control of blood flow to your penis. 

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, improving your sexual function and sex life in general.

It’s important to understand that Cialis and Viagra aren’t sex pills. If you’re not already sexually aroused, they won’t do the hard work for you. Instead, they make it easier to get and stay hard when you’re already in the mood for sex.

Generally, there is no major difference in the effectiveness of Viagra vs Cialis. Both tablets can be taken at least 30 minutes to an hour before sex. The difference lies primarily in the effective windows of each medication: Viagra can last up to four hours, while Cialis lasts around 36 hours.

Because both drugs work by affecting the blood vessels that supply your penis, you should be careful 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 steps you can take to use Cialis or Viagra as safely as possible — further down the page.

To get a sense of how the medical community views each medication and their different ideal use cases:

Viagra 101

Arguably the most well-known ED medication of all, Viagra contains the active ingredient sildenafil.

• Sildenafil citrate (generic Viagra) is considered an on demand treatment for erectile dysfunction, meaning it’s taken as needed.

• It was developed in the ‘80s and ‘90s as a treatment for angina (a type of chest pain caused by certain heart conditions). 

• During testing, the researchers behind sildenafil discovered that although it was effective as an angina treatment, it was more effective at helping men get erections, largely because it increases blood flow to the penis.

• Viagra was approved by the FDA as a treatment for erectile dysfunction in 1998. It’s now sold as brand name Viagra and as generic sildenafil. 

It takes around 30 to 60 minutes for a normal dose of Viagra to begin working and provide relief from erectile dysfunction.

Cialis 101

Also a prescription erectile dysfunction medication approved by the FDA, Cialis contains the active ingredient tadalafil.

• Tadalafil or generic Cialis can be taken either on demand or as a daily ED medication.

• It came onto the market a little later than Viagra, first receiving approval as a prescription ED medication in 2003.

• Like sildenafil, it comes as an oral tablet for use before sex. 

• Cialis isn’t solely used to treat ED. It’s also used to treat the symptoms of benign prostatic hyperplasia (BPH), a form of enlarged prostate that’s common in middle-aged and older men. 

It can be taken as needed or daily, and is often referred to as the “weekend pill” thanks to its long-lasting effects.

Does Cialis work better than Viagra? It depends who you ask. One of the main reasons people consider Cialis to be “better” than Viagra is that Cialis lasts longer. Cialis can last for up to 36 hours per dose, whereas a single dose of Viagra usually provides relief from ED for around four hours.

Put simply, Cialis works like a weekend pill for ED, hence its nickname, while Viagra is more of an evening pill. 

If you like to have sex more than once a day, or if you prefer the idea of taking a single pill for a weekend versus taking medication every night, you’ll probably prefer Cialis over Viagra.

On the other hand, if you’re only interested in short-term relief from ED, such as for a night out, or if you want to limit the amount of time your medication is active in your body (and, therefore, the amount of time you experience potential side effects), Viagra could be a better choice for you. 

There are other factors about each medication to consider, 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 ending sooner or later based on factors such as your body weight, your eating habits or certain medical conditions.

Cialis and Viagra are both fast-acting medications that should produce noticeable improvements in your erections and sexual function within 30 minutes to two hours.

On average, it takes around 30 to 120 minutes for Cialis to start working. Most research suggests that Cialis reaches its peak concentration in your blood after about two hours.

Similarly, Viagra typically starts to work after 30 to 60 minutes.

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:

• Take your medication around an hour before sex. This way, your medication will be either 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” your medication. Try to remember how long it takes before you notice improvements in your erections after taking your ED medication. This way, you’ll know how early to take Cialis or Viagra in the future.

• Avoid eating too much food before using ED medication. Some ED medications can take longer to begin working if they’re taken with a large, fatty meal. We’ve discussed the effects of high-fat meals on ED medication in more detail below.

Follow other medical advice to improve your erections. Making simple, meaningful changes to your daily habits, such as maintaining a healthy weight and eating a healthy diet, can also help to improve your erectile function and performance in bed.

Our guide to maintaining an erection naturally shares lifestyle tips that you can use with Viagra or Cialis for improved erections and better health.

Cialis and Viagra are both highly effective as treatments for ED. Both are approved by the FDA, meaning they’ve passed through an extensive process of clinical trials showing that they’re both safe and effective for most men.

Most studies show that more than 80 percent of men with ED who take either medication find it easier to get and stay hard. 

For example, in an article published in the journal Clinical Interventions in Aging, experts found that 88 percent of men with erectile dysfunction reported successful erections after using 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 similar study published in the journal BMC Urology also found that 91 percent of men with ED reported improved erections after using Viagra before sex.

It's important not to get wrapped up in the minutiae here. Although there are slight differences in these numbers, both Cialis and Viagra are extremely effective at treating ED, and neither medication is “better” than the other.

The real difference is the amount of time each medication works, which is something you’ll want to keep in mind when discussing ED medications with your healthcare provider. 

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, taking these medications at the same time as eating certain foods can affect the rate at which they’re absorbed and able to become effective. 

Viagra and Cialis can both be taken without any regard to your food intake. However, according to the FDA, taking Viagra with a meal that’s high in fat might slow down its absorption, meaning it could take longer to start working.

This effect doesn’t appear to be very large, meaning you shouldn’t worry too much about what you eat when you’re using Viagra.

However, if you notice that Viagra is a little slow to start working for you, you might want to opt for a lighter meal or just taking it on an empty stomach versus taking it with something like a burger, steak or pizza.

Not only should this help with absorption, but  it’s also an easy way to reduce your risk of feeling bloated in the bedroom. 

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. 

You can find the most common side effects of Viagra and Cialis below, along with information on the percentage of men who report these side effects at the minimum and maximum doses:

Common Viagra Side Effects

• Headaches (16 to 28 percent)

• Flushing (10 to 19 percent)

• Upset stomach (three to 17 percent)

• Abnormal vision, including changes in color vision, blurred vision and/or increased sensitivity to light (one to 11 percent)

• Nasal congestion (four to 9 percent)

• Back pain (three to four percent)

• Muscle pain (two to four percent)

• Nausea (two to three percent)

• Dizziness (three to four percent)

• Skin rash (one to three percent)

Common Cialis Side Effects

• Headaches (three to 15 percent)

• Upset stomach (four to ten percent)

• Back pain (three to six percent)

• Muscle pain (one to four percent)

• Nasal congestion (two to three percent)

• Flushing (one to three percent)

• Pain in limbs (one to three percent)

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

In very rare cases, Cialis and Viagra may cause priapism. Priapism is a painful and prolonged erection that requires immediate care from a medical professional.

If you experience a painful, persistent or uncomfortable erection after using Viagra, Cialis or any other type of erectile dysfunction medication, it’s important to go to the emergency room immediately.

As we mentioned, most of the time, side effects from ED medications get better over time. But because Cialis has a much longer half-life than Viagra, you may experience Cialis side effects for longer.

If you’re prone to side effects from any type of ED medication, you might benefit from adjusting your dosage.

Make sure to talk to your healthcare provider before making any changes to the way you take Viagra or Cialis, including reducing your dose of either medication. 

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, while our full guide to Viagra (sildenafil) side effects goes into more detail about the potential adverse effects of this medication.

Cialis and Viagra can both interact with other medications, including several medications used to treat hypertension (high blood pressure) and other cardiovascular health issues.

When used with nitrates, Cialis and Viagra can produce a sudden drop in blood pressure levels that may cause dizziness, lightheadedness, fainting and serious cardiovascular events, such as heart attack or stroke.

In addition to prescription nitrates such as nitroglycerin, other nitrate/nitrite products that interact with Cialis and Viagra include recreational “poppers”.

Cialis and Viagra can also interact with other medications, including:

• Alpha-blockers

• Guanylate cyclase stimulators

• Oral antifungal medications

• Other hypertension medications

• Other erectile dysfunction medications

• HIV protease inhibitors

• Some antibiotics

If you’re prescribed any type of medication, or if you occasionally use recreational drugs, make sure to inform your healthcare provider before using Cialis, Viagra or any other ED medication.

When used as prescribed, and without any drugs that could cause interactions, Cialis and Viagra are both safe medications for most men.

In addition to paying attention to drug interactions, you can keep yourself safe while using Cialis or Viagra by taking the following steps:

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

• Avoid grapefruit. Research suggests that grapefruit juice could affect the strength of Cialis and Viagra due to its effects on certain liver enzymes. As such, it’s best to avoid anything that contains grapefruit while you're using either medication.

• Talk to your healthcare provider if you have any health conditions. Some medical conditions, such as heart disease, high blood pressure, low blood pressure and others, may make it unsafe for you to use Cialis or Viagra.
  To keep yourself safe, make sure to let your healthcare provider know if you have any underlying health conditions or if you’ve had a heart attack or stroke, before taking medication to treat ED. 

Cialis and Viagra both come as tablets, but the two medications have very different dosages of their active ingredients. 

Cialis comes in four different doses:

• Cialis 10mg. This is the recommended starting dose of Cialis. Your healthcare provider might 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 experience any improvements with a 10mg dose of Cialis, taking Cialis at a dosage of 20mg may improve your results.

• Cialis 2.5 and 5mg. Referred to as “Cialis Daily,” these lower-dose tablets of Cialis are designed for men with ED who like to have spontaneous sex and prefer a daily dose to using Cialis as needed. The 5mg dose is also sometimes prescribed as needed.

Viagra comes in three different doses:

• Viagra 50mg. This is the typical recommended initial dose of Viagra. Your healthcare provider might prescribe Viagra at this dose if you’re young, if you only have mild to moderate ED, or 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 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 provide generic sildenafil from $3 per use, and brand name Viagra available 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.

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 feel like it, you’ll probably enjoy the long-lasting effects offered by Cialis. 

• 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. 

There are also other options available for treating ED, such as Stendra® (avanafil) — a newer, FDA-approved medication that’s faster acting and less likely to cause side effects.

If you’re struggling with ED, help is available. We offer a range of ED treatments online following a private consultation with a healthcare provider.

You can also learn more about treatment options for improving your erections and having better sex with our detailed guide to the most common erectile dysfunction treatments and drugs.