Can You Take Cialis in the Morning and Viagra at Night?

By definition, erectile dysfunction (ED) is a continuing inability to get and maintain an erection firm enough for sexual intercourse.

Several medications are effective treatments for ED, including Cialis and Viagra. To minimize the chance of experiencing adverse effects, follow the advice of the drug manufacturers and your healthcare provider. Mixing Cialis and Viagra is not recommended.¹ Here’s why.

Have you considered clinical trials for Erectile dysfunction?

We make it easy for you to participate in a clinical trial for Erectile dysfunction, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

What are Cialis and Viagra?

Cialis (tadalafil) and Viagra (sildenafil) are the two most common phosphodiesterase inhibitor (PDE5 inhibitor) medications in the world.² 

Both drugs have been approved by the US Food and Drug Administration (US FDA) as safe and effective treatments for ED.³ ⁴ 

How do they work?

All PDE5 inhibitors work similarly. 

Neither Cialis or Viagra directly causes an erection, and these medications are not a cure for ED.⁵ 

Rather, they treat the symptoms of ED by increasing blood flow to the penis. You also need to be sexually aroused for Cialis and Viagra to work.⁶ ​​ 

Phosphodiesterase is an enzyme in the body that prevents erections from occurring. It breaks down a molecule called cyclic GMP which relaxes the muscles in the blood vessels and helps to increase blood flow to the penis, so an erection can happen. 

PDE5 inhibitors — including Cialis and Viagra — block the phosphodiesterase enzyme from having this effect on cyclic GMP. 

This process allows an erection to take place. 

Can you take Cialis and Viagra at the same time?

Unless your doctor directs you to do so, it’s not recommended to take Cialis and Viagra on the same day. (Cialis stays in your body for approximately 36 hours).⁷ 

Cialis and Viagra are mainly taken on an as-needed basis when having difficulty achieving an erection. 

Typical instruction is to take either Cialis or Viagra around 30 minutes before having sex.,⁸ ⁹ 

If you follow all the guidelines for taking either Viagra or Cialis, and you continue to experience ED, speak to a healthcare professional instead of taking the two drugs in the same day. A doctor can screen you for underlying health issues and present you with different treatment options and (possibly) medication adjustments.

What might happen if you take them at the same time?

In most instances, taking Viagra and Cialis together would have similar effects to taking a double dose of either medication, which could be dangerous and ineffective. 

Similarly, it’s not safe to take Cialis in the morning and then take Viagra the same night because Cialis lasts up to 36 hours in the body.¹⁰ 

In other words, if you were to take Cialis in the morning, it would still be in your system when you take Viagra later that day. 

Wait at least 36 hours before taking Viagra, another dose of Cialis, or any other PDE5 inhibitor. 

Likewise, if you take Viagra at night, you shouldn’t take Cialis or any other PDE5 inhibitor the next morning. 

Although Viagra is generally only effective for a few hours, it can still linger in your system, so wait at least 24 hours. 

Although you should not take Cialis and Viagra simultaneously or within 36 hours, it may be okay to alternate outside this timeframe. 

Still, it’s best to seek guidance from your prescribing doctor before you do. 

What are the side effects of taking them together?

Taking Cialis and Viagra together doesn’t offer a combined beneficial effect on ED. 

Although Cialis and Viagra aren’t known to interact dangerously (they are both the same type of medication), you will be increasing the overall risk of side effects. 

You will end up with more than the recommended amount of PDE5 inhibitor in your system. 

So, you might experience symptoms much like after taking too much Viagra or Cialis. These side effects may include (but are not necessarily limited to):

Low blood pressure

PDE5 inhibitors can reduce your blood pressure. However, if you take two inhibitors, your blood could drop to dangerously low levels. You might feel this as being dizzy, lightheaded, or nauseous.¹¹ 

Prolonged and potentially painful erection

Priapism is a prolonged erection that lasts more than four hours. Priapism can lead to permanent ED and damage to the penis, so it should be treated as a medical emergency.

How do you know if you're taking too much?

You will likely experience the above side effects of dangerously low blood pressure or a prolonged painful erection if you take too much Cialis or Viagra. 

Cialis and Viagra are designed to be taken as needed. 

However, Cialis has a low-dose option, so your doctor may prescribe it as needed or taken daily. ¹²

Standard doses of Viagra are: 

  • 25mg

  • 50mg

  • 100mg

Standard doses of Cialis are: 

  • 2.5mg (daily use)

  • 5mg

  • 10mg (typical occasional use dosage)

  • 20mg

It’s important to note that men over the age of 65 and men with impaired liver or kidney function are at higher risk of side effects. ¹³

This risk is related to having a slower average rate at which the medications clear from the body. If you happen to be in one of these demographics, a lower dose will usually be prescribed. 

Can you overdose on these medications?

Overdose is rare, but it is possible to overdose on Cialis or Viagra, or have a fatal drop in blood pressure when too much is taken., ¹⁴ ¹⁵

If you take too much Cialis or Viagra, seek urgent medical attention and contact your local poison control helpline for support. 

Can you drink alcohol when taking Cialis or Viagra?

Drinking alcohol in moderation is considered safe when using Cialis or Viagra. However, excessive alcohol use is dangerous. 

Both drugs widen blood vessels and reduce blood pressure

Since alcohol also widens blood vessels and drops blood pressure, it can have  dangerous interactions with how Viagra and Cialis are metabolized.¹⁶ In rare situations, this could be life-threatening.

Also, chronic alcohol use increases the risk of sexual dysfunction, so those with ED would be well-advised to avoid alcohol.¹⁷

What medications can't be taken with Cialis or Viagra?

You should inform your doctor about all other medications you take, including supplements and recreational drugs. 

Certain medications can have dangerous interactions with Cialis and Viagra. They can have serious effects like a sudden drop in blood pressure.

Cialis and Viagra should not be taken with:

  • Other PDE5 inhibitors Inhibitor drugs including Stendra (avanafil) and Levitra (vardenafil) should not be taken together.

  • Blood pressure medications Alpha-blockers are unsuitable, though some individuals may be able to take them with close monitoring.¹³

  • Vasodilators Nitrates that treat heart failure, such as nitroglycerin, should not be taken with Cialis and Viagra.

  • Recreational drugs Party drugs, especially stimulants, don’t mix with Cialis and Viagra. For example, cocaine decreases blood flow, while ED medication increases it. This can cause sudden fluctuations and can induce a stroke or heart attack. If you have a history of heart problems, the risks are even higher.¹⁸

Food and drugs that change Cialis and Viagra levels

Taking any of the following may cause your body to eliminate your medication slowly or process it differently than usual: 

  • Antibiotics Antibiotics such as erythromycin elevate PDE5 inhibitors.¹⁹

  • Antifungals Ketoconazole can elevate PDE5 inhibitors.²⁰

  • Protease inhibitors  HIV medication such as ritonavir may or may not be suitable.²¹ Ask your doctor.

  • CYP3A4 inducers Drugs like phenobarbital, rifampicin, phenytoin, St. John’s Wort, or glucocorticoids can decrease the effectiveness of Cialis and Viagra.²²

  • Grapefruit or grapefruit products Grapefruit and its juice can delay the metabolism and increase the amount of the drug in the blood.²³

Are there any side effects of taking Cialis or viagra?

Cialis and Viagra have similar side effects. 

Most side effects are temporary and mild to moderate in severity.  

Side effects can include: 

  • Headache

  • Heartburn

  • Diarrhea

  • Flushing of the face (more common with Viagra)²

  • Difficulty sleeping or waking

  • Runny nose

  • Feeling numb or tingly in the limbs

  • Muscle aches and pain (more common with Cialis)²

  • Sensitivity to light 

Cialis can also cause coughing and indigestion. These symptoms are less frequently reported when taking Viagra.⁸ 

One study found that sildenafil, the active ingredient in Viagra, had a higher rate of adverse effects than tadalafil, the active ingredient in Cialis.⁸ 

However, since Viagra lasts a shorter time in the body, the side effects may not be experienced for as long as they are with Cialis. 

There are also some serious side effects of Viagra and Cialis, which you should seek medical attention⁸ for. These include :

  • Vision changes: blurred vision or a sudden loss of vision

  • Hearing changes: ringing in ears or sudden decrease or loss of hearing

  • Fainting, dizziness, or feeling lightheaded

  • Chest pain

  • Low blood pressure

  • Shortness of breath

  • A prolonged, painful erection that lasts more than four hours

  • A rash

  • Itching or burning during urination

  • Heart complications, like heart attacks, strokes, and irregular heartbeats

  • Hives, swelling, blistering, and/or peeling of the skin (more likely with Cialis) 

When should you see a doctor?

See your doctor if you notice t an ongoing problem with achieving erections. 

This is important so you can begin treatment, but also because ED can be caused by numerous underlying conditions you’re unaware of. 

Viagra and Cialis are both prescription drugs, so you will need to see your doctor before being able to use them. 

If Cialis or Viagra isn’t working the way you’d like it to, you should also speak with your doctor to see if your dose needs to be adjusted or discuss switching medications from Viagra to Cialis or vice versa.

Also, if you experience side effects, see your doctor. There are other medications and treatments in addition to PDE5 inhibitors, which you may be better suited to. 

The lowdown

Cialis and Viagra are popular treatments for ED. Both have similar effectiveness and function in the body and are regarded as generally safe when taken as directed. You may be able to alternate between Cialis and Viagra. Still, you shouldn’t take them simultaneously, nor should you take Cialis in the morning and Viagra at night.

  1. Tadalafil in the treatment of erectile dysfunction (2008)

  2. Direct comparison of tadalafil with sildenafil for the treatment of erectile dysfunction: A systematic review and meta-analysis (2017)

  3. FDA approves Cialis(R) (tadalafil) for once daily use for the treatment of erectile dysfunction | Lilly Investors

  4. Public notification: U.S.A viagra contains hidden drug ingredient | U.S. Food and Drug Administration

  5. Phosphodiesterase-5 (PDE5) inhibitors in the management of erectile dysfunction (2013)

  6. Questions and answers for Cialis (tadalafil) | U.S. Food and Drug Administration

  7. Cialis (tadalafil) | Accessdata.fda.gov

  8. Tadalafil | MedlinePlus

  9. Sildenafil | MedlinePlus

  10. Tadalafil in the treatment of erectile dysfunction (2008)

  11. Sildenafil (Oral route) | Mayo Clinic

  12. Cialis (tadalafil) tablets, for oral use | Accessdata.fda.gov

  13. Viagra (sildenafil citrate) tablets | Accessdata.fda.gov

  14. Cialis overdose | Drugsdb.com

  15. 10‐Year analysis of adverse event reports to the food and drug administration for phosphodiesterase type‐5 inhibitors (2012)

  16. Influence of alcohol on phosphodiesterase 5 inhibitors use in middle- to old-aged men: A comparative study of adverse events (2019)

  17. Prevalence of sexual dysfunction in male subjects with alcohol dependence (2007)

  18. The rise of viagra abuse: Doctors warn against worrying 'sextasy' trend - Where ecstasy is mixed with drug to enhance euphoria | Mail Online

  19. The effects of steady-state erythromycin and azithromycin on the pharmacokinetics of sildenafil in healthy volunteers (2002)

  20. Effect of ketoconazole on the pharmacokinetics of udenafil in healthy Korean subjects (2010)

  21. Viagra and protease inhibitors (1998)

  22. Drug metabolism - The importance of cytochrome P450 3A4 | Medsafe

  23. Drug interactions with phosphodiesterase-5 inhibitors used for the treatment of erectile dysfunction or pulmonary hypertension | New Drugs and Technologies

Other Sources:

Have you considered clinical trials for Erectile dysfunction?

We make it easy for you to participate in a clinical trial for Erectile dysfunction, and get access to the latest treatments not yet widely available - and be a part of finding a cure.

Joining community groups and exercise programs for my condition made me feel empowered – but I want to be part of finding a cure.
Peter, 64

Have you considered clinical trials for Erectile dysfunction?

Do you want to know if there are any Erectile dysfunction clinical trials you might be eligible for?
Have you taken medication for Erectile dysfunction?
Have you been diagnosed with Erectile dysfunction?


Join our email list

Want all the latest clinical trial and HealthMatch news in your inbox? We thought you might! Sign up below.