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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 5/11/2021

Used by millions of men in the United States alone, Cialis (also known under the generic name tadalafil) and Viagra (sildenafil) are two of the most popular brand name drugs for treating erectile dysfunction—and for good reason. 

They both have similar effects, they both treat erectile dysfunction, and they both pump up sexual performance. But when it comes to the battle of Cialis vs. Viagra, which contender wins out?

The truth is, there are a few key differences between Cialis and Viagra that can make one medication a better choice than the other.

Below, we compare Cialis and Viagra to help you know which might be best for you. Learn about factors like the amount of time each drug lasts and takes to work, along with potential side effects and interactions you need to be aware of before using either medication.

How Cialis and Viagra Work 

Before we get into the differences between Cialis and Viagra, it’s important to explain how these drugs work.

Cialis contains a substance called tadalafil. Tadalafil is part of a class of drugs called PDE5 inhibitors (phosphodiesterase type 5 inhibitors) that work by increasing blood flow to the soft tissue of your penis. 

The increased flow to the blood vessels in turn makes it easier for you to get and keep an erection when you’re sexually aroused.

Viagra contains a substance called sildenafil. And just like tadalafil, sildenafil is a PDE5 inhibitor that increases blood flow to the soft, erectile tissue of your penis.

Because both drugs work by increasing blood flow, they can also be used to treat health conditions like hypertension.

If you have heart disease, use medication for high blood pressure, or have another medical condition, it’s important to seek medical advice from a healthcare professional prior to using ED treatments like Cialis or Viagra.

Does Cialis or Viagra Last Longer? 

The biggest difference between Cialis and Viagra is the amount of time each drug stays active in your body.

Cialis is a long-lasting erectile dysfunction drug, and on average, can work for up to two days after you take it. Because it lasts so long, it’s been dubbed the “weekend pill” by users and the mass media.

If you are having trouble getting an erection but don’t know exactly when you will have sexual activity, Cialis could be a great choice. Whether you’re going away for a weekend or just want to be prepared for a spontaneous sexual encounter, a single dose of Cialis is usually more than enough.

Viagra, on the other hand, is a shorter-acting erectile dysfunction drug. Most of the time, Viagra lasts for five to six hours, with the effects of the medication usually starting to wear off three to four hours after you take it.

This means Viagra is a great choice if you need a short-acting erectile dysfunction drug to keep you hard and self-confident for one evening. It’s worth discussing your situation with a health provider to determine which ED treatment might be right for you. 

It’s important to remember that Cialis and Viagra don’t always last for exactly 24-36 or five to six hours. Factors such as your body weight, eating habits and cardiovascular health can affect how long each medication provides relief from sexual dysfunction.

Verdict: Cialis lasts longer and is better for weekends, whereas Viagra is usually a better choice if you only need to treat ED for one evening.

Related Post: Is Viagra Over The Counter?

Which Drug Works Faster? 

Cialis and Viagra both start working quickly after you take them. A normal dose of Cialis usually starts to produce an improvement in your erections after about 30 minutes. However, it can take up to two hours for Cialis to become fully effective.

Most of the time, Viagra starts working in about 30 minutes. It can take up to one hour for Viagra to become fully effective, meaning you’ll want to take it an hour or more before you plan to have sex for best results.

Verdict: Cialis and Viagra both start to work in 30 minutes from consumption, but can take about an hour to produce optimal results. Cialis can also take up to two hours to reach its full concentration.

Which Drug is More Effective: Cialis or Viagra?

Cialis and Viagra are both effective treatments for erectile dysfunction. Clinical trials of both medications show that more than 80 percent of men are able to achieve satisfactory erections at the recommended dose:

  • In a clinical trial of Cialis, 81 percent of men reported that the medication gave them improved erections. 71 percent of men with severe erectile dysfunction reported improved erections from Cialis.

  • In a clinical trial of Viagra, 82 percent of men reported improved erections after taking a 100mg dose of the medication. Viagra was also effective at lower doses, with 62 percent and 74 percent of men reporting improvements at 25mg and 50mg doses, respectively.

Verdict: Cialis and Viagra both work well for treating ED, with no real difference between the two drugs in terms of erection quality or sexual performance.

Are Viagra and Cialis Affected by Food?

Cialis is not affected by food, meaning it will start working in roughly the same amount of time regardless of whether you take it on an empty or full stomach.

Viagra, on the other hand, can be affected by your food choices. While you can take it with or without food, eating a high-fat meal before taking Viagra can slow the drug’s absorption, meaning you might not notice the medication’s effects of Viagra for more than one hour after taking it.

For best results, you should take Viagra on an empty stomach at least one hour before having sex (but, you can take Viagra with food if needed as well).

If you need to eat before taking Viagra, try to avoid foods with a high-fat content, as they’re most likely to slow your body’s absorption of the medication.

Verdict: Because Cialis is unaffected by food, it’s a better option if you need to eat before taking your ED medication.

Cialis Side Effects vs. Viagra Side Effects

Side effects of Viagra and Cialis are similar in nature because the drugs affect the body in a lot of the same ways. The most common side effects of both drugs are:

    • headaches 
    • nasal congestion/stuffy nose
    • back pain
    • chest pain
    • facial flushing
    • heartburn
    • upset stomach/indigestion 
    • chest pain
    • temporary blurred vision 
    • dizziness 
    • muscle aches
  • sore throat

Viagra and Cialis side effects usually occur while the medications are active. However, it’s also possible for some common side effects (particularly headaches and heartburn/indigestion) to occur as the drugs are becoming less active in your body.

Cialis and Viagra can also both cause priapism (an erection that lasts for four hours or longer), yet this is a rare side effect

If you experience a lasting, persistent erection for four hours or longer after using either drug, seek medication attention as soon as possible.

Because Cialis stays in your body longer than Viagra, you might notice Cialis side effects for longer. If you’re prone to side effects, Viagra’s shorter duration of action can make it a better option.

You can also reduce your chances of experiencing side effects of Cialis and Viagra by taking a lower dose of the medication.

Verdict: side effects from Cialis and Viagra are nearly identical. However,  Cialis side effects may last longer than those of Viagra because Cialis stays in the body for a longer amount of time.

Read more about what you should expect from erectile dysfunction medication.

Which Is Safer: Cialis or Viagra?

Cialis and Viagra have excellent overall safety records. However, Cialis and Viagra can become unsafe if used with certain other medications:

  • If you use nitrates or other medications to treat hypertension, you should not use Cialis or Viagra. When combined, nitrates and PDE5 inhibitors can cause blood pressure to drop, which can lead to serious health issues.

  • While it’s perfectly safe to have a glass of wine or beer or any other light drink after taking Cialis or Viagra, you should avoid drinking heavy amounts of alcohol when taking either drug. The combination of alcohol and a PDE5 inhibitor can lead to orthostatic hypotension (low blood pressure after standing up from a prone position).

  • Grapefruit and grapefruit juice can affect the way your body metabolizes tadalafil and sildenafil, the active ingredients in Cialis and Viagra. When you’re using these drugs, you’ll need to avoid any foods that contain grapefruit.

  • If you have heart disease, a history of heart attack or other health conditions, you’ll need to inform your healthcare provider before considering Cialis or Viagra.

Overall, Cialis and Viagra are both safe, effective drugs. As with all prescription medicine, you’ll need to talk to a healthcare provider about your symptoms and overall health before using either drug to treat erectile dysfunction.

Verdict: Aside from the four situations listed above, Cialis and Viagra are both safe drugs with few serious side effects.

Cialis and Viagra Dosages

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

Cialis comes in four different dosages:

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

  • 20mg. This is the highest available dose of Cialis. If you don’t respond to the 10mg dose or find it doesn’t provide enough of an improvement, talk to your healthcare provider about switching to the full 20mg dose.

  • 2.5 and 5mg. This amount of Cialis is intended as a daily dose. Known 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:

  • 50mg. This is the recommended starting dose of Viagra. Your healthcare provider will likely prescribe Viagra at this dosage if you’re young, have mild to moderate ED, and haven’t previously used Viagra or any other ED medications.
  • 100mg. This is the highest available dose of Viagra. This dose is usually prescribed if you don’t notice enough of an improvement from the 50mg tablet.
  • 25mg. This is the smallest available dose of Viagra. Many younger men and men with mild ED notice an improvement from this dose of Viagra. This dose is also less likely to cause side effects.

Verdict: Cialis and Viagra are both available at different dosages, making it easy to take just the right amount of either medication for your needs.

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’d like without having to plan ahead, you’ll probably prefer 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 Viagra.

Learn More About Erectile Dysfunction Treatments

Looking for a reliable, science-backed treatment for erectile dysfunction? We’ve got you fully covered. Our guide to the most common erectile dysfunction treatments compares the three most common ED medications: Viagra (sildenafil), Cialis (tadalafil) and Levitra (vardenafil).

You can also learn more about how to use erectile dysfunction drugs in our guide to using ED medication effectively, which covers everything from how to eat before using Viagra and other PDE5 inhibitors, to potential drug interactions.

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.