Feel better, faster. Get started

What Is Cialis? Side Effects, Usage, Dosage & More

By Chesney Fowler, MD bool(true)
Medically reviewed
April 8, 2021

Cialis is a prescription, brand-name medication approved by the Food and Drug Administration (FDA) to treat symptoms of erectile dysfunction (ED) and benign prostatic hyperplasia (BPH). 

Cialis is a safe and effective option for most men affected by one of these conditions. Cialis can also be used to treat symptoms of ED and BPH together. Because Cialis is only available by prescription, it’s important to talk to a healthcare professional to determine if Cialis is right for you. 

To help you prepare for that conversation, this article describes who can take Cialis, how to take it, and how long it lasts, as well as its side effects, drug interactions, alternatives, and cost.

What Is Cialis?

Cialis is a brand name of the prescription drug tadalafil. It comes as an oral tablet.

Erectile dysfunction prescriptions for as low as $0.90 per dose

Get started

What Is Cialis Used For?

Cialis is a popular medication used in the treatment of erectile dysfunction (ED). It is also used to treat benign prostatic hyperplasia (BPH, or prostate gland enlargement). 

Cialis is a phosphodiesterase-5 (PDE5) inhibitor, meaning it works to block the enzyme PDE5. By doing so, Cialis helps to relax the penile muscles, expand blood vessels that go into the penis, and improve penile blood flow during sexual stimulation. This ultimately helps men get and maintain better erections. 

In the treatment of BPH, Cialis helps relax the bladder and prostate muscles to improve symptoms such as painful or frequent urination.

Side Effects

Like all medications, side effects can occur when taking Cialis. The most common side effects include:

  • Headache
  • Indigestion
  • Back pain
  • Nasal congestion
  • Flushing
  • Muscle aches
  • Pain in arms or legs

Serious side effects include:

  • Low blood pressure
  • Erections that last longer than four hours
  • Hearing loss
  • Vision problems

If you experience any of these, contact a healthcare provider immediately.

How to Take Cialis

There are two ways to take Cialis: as a daily medication, or as needed.

If you use it as a daily medication in the treatment of ED, take Cialis with a glass of water with or without food at the same time every day. The most common recommended dosage for daily usage is between 2.5 mg (milligrams) and 5 mg.

If you use Cialis as needed to treat ED, take the pill with a glass of water with or without food at least 30 minutes before sexual activity. The medication can last in your system for up to 36 hours, so it’s important to not take more than one dose of Cialis per day if you’re taking it as needed. The most common recommended dosage in this case is 10 mg.

When prescribed for the treatment of BPH, most doctors prescribe a daily medication of 5 mg.

Keep in mind that dosing varies based on your symptoms, medical history, other medications, and response to the medication. Work with your healthcare provider to determine the correct dosing for you. 

How long does Cialis last?

Cialis takes about 30 minutes to take effect (but may take up to two hours) and can last in your system for up to 36 hours. Regardless of the condition you’re treating, do not take more than one dose every 24 hours.

Can women take Cialis?

Cialis is not FDA-approved for the use in women. However, women with a low sex drive have other medication options, including the injectable bremelanotide (Vyleesi) and the pill flibanserin (Addyi).

Women with pulmonary arterial hypertension (PAH) can take Adcirca, which has the same active ingredient as Cialis, tadalafil. However, women with PAH should not take Cialis.

Precautions 

Whenever you start a new medication, it’s important to talk to your healthcare provider about any known allergies, medical conditions, and other medications. Cialis may not be suitable for people with the following conditions: 

  • Heart disease: In some cases, Cialis may have heart health benefits. However, it is not appropriate for all heart conditions and may cause serious complications or side effects in some individuals with heart disease.
  • High or low blood pressure: If you have low blood pressure, high blood pressure, coronary artery disease, arrhythmias, or have had heart attacks or strokes in the past, Cialis may not be safe for you. 
  • Liver or kidney disease: Cialis is not recommended for people with liver or kidney problems.
  • Sickle cell anemia: Cialis may cause adverse effects in people with sickle cell anemia.
  • Peyronie’s disease: Cialis may not be appropriate in certain patients with a penis deformity or curvature. Talk with your provider.
  • Retinitis pigmentosa: Speak with your healthcare provider if you have this genetic eye disease or any other chronic eye condition.
  • Bleeding disorders or peptic ulcers: Your provider may want to monitor you closely or consider other treatment options if you have either of these conditions.
  • Leukemia, multiple myeloma, and other cancers: Cialis may cause serious side effects in people with certain cancers.

Drug Interactions

Cialis can interact with other medications. Talk with your healthcare provider if you’re on any of the following, and always let your prescriber know about all medications and supplements you take: 

  • Alpha blockers: Medications like doxazosin and tamsulosin can interact with Cialis, producing serious side effects such as dangerously low blood pressure.
  • Nitrates: Nitrates, nitroglycerin-based medication, and other medications prescribed to treat chest pain and angina (including amyl nitrite) can cause a serious reaction or even death when combined with Cialis or other similar medications. 
  • Riociguat (Adempas): Guanylate cyclase stimulators like riociguat can cause side effects like dangerously low blood pressure when combined with Cialis.
  • St. John’s wort: Some herbal and over-the-counter remedies can change the level of Cialis in your bloodstream, leading to serious side effects. Make your prescriber aware of any supplements you take.
  • Antibiotics: Some antibiotics, including clarithromycin, erythromycin, and telithromycin, can increase blood levels of Cialis, causing unwanted and sometimes dangerous side effects including low blood pressure or priapism (prolonged erections). Rifampin and other antibiotics may lower the level of Cialis in your blood, reducing its efficacy. Let your prescriber know you are taking Cialis before starting a new antibiotic.
  • HIV medication: Certain HIV medications and protease inhibitors can raise levels of Cialis in your blood, causing unwanted and potentially dangerous side effects, including priapism.
  • Oral antifungals: Some antifungals like ketoconazole and itraconazole may raise Cialis levels in your blood.
  • Other ED medications: Viagra (generic sildenafil) and Levitra (generic vardenafil) should not be combined with Cialis, as this may increase the risk of side effects.

Alcohol and food interactions

Here are some other considerations to make before taking Cialis:

  • Alcohol: Consuming large quantities of alcohol while taking Cialis can cause effects such as dilated blood vessels, dizziness, headache, fast heartbeat, and low blood pressure. Talk with your healthcare provider about your regular alcohol consumption before starting Cialis.
  • Grapefruit: Eating grapefruit or drinking grapefruit juice can increase the levels of Cialis in your blood, raising your risk for side effects.

Cost of Cialis

The cost of Cialis varies depending on the recommended dosage and your insurance. However, because it’s a brand-name medication, it will cost more than its generic alternative, tadalafil.

Alternatives to Cialis: Cialis vs. Viagra vs. Levitra

For the treatment of ED, two popular alternatives to Cialis exist: Viagra and Levitra. For the treatment of PAH, one alternative to Cialis exists: Adcirca. 

Here is how the three compare to Cialis.

Cialis vs. Viagra

Viagra is often the first-line medication offered by doctors to treat ED because it’s been on the market longest, so its side effects and drug interactions are well known. It can be prescribed as an oral tablet, oral liquid, or subcutaneous injection. 

Unlike Cialis, Viagra is designed specifically to be taken as needed shortly before sexual activity. It can take anywhere from 30 minutes to an hour to take effect and stays in your system for 4-5 hours, whereas Cialis can stay in your system for up to 36 hours and can help men become erect anytime during that window. The most common dose is 50 mg. Unlike Cialis, you cannot take Viagra with food; it’s most effective when taken on an empty stomach.

Though Viagra can cause much of the same side effects as Cialis, it can also cause dizziness, nausea, rash, and abnormal vision. The one side effect that Cialis can cause that’s not experienced with Viagra is pain in the arms or legs.

Both medications are approved as effective and safe options to treat ED in men, but a study published in 2015 found that 69% of men preferred using Cialis over Viagra. When citing the reason behind their preference, most men said that they preferred Cialis because it lasts longer in the body.

Cialis vs. Levitra

Levitra is another oral medication used to treat ED. It works similarly to Viagra: It’s taken as needed, with or without food, about an hour prior to sexual activity. It takes effect within 30 minutes to two hours and lasts for 4-5 hours. The most common dose is 10 mg.

Though Levitra can cause many of the same side effects as Cialis, it can also cause dizziness, nausea, kidney problems, flu-like symptoms, and sinus infection. The one side effect that Cialis can cause that’s not experienced with Levitra is pain in the arms or legs.

Can You Buy Cialis Online?

Cialis is only available with a prescription but can be purchased online with the approval of a prescriber. With K Health, you’ll find the lowest possible cost for Cialis—and shipping and doctor’s consultations are always free.

When to See a Doctor

If you’re struggling with symptoms of ED or BPH, talk with a healthcare professional to see if Cialis is right for you. It is important to discuss any existing medical conditions, medications, supplements, and alcohol consumption

If you’ve already started Cialis but experience unwanted side effects, talk to your prescriber. They may recommend a change in dosage or medication.

Erectile dysfunction prescriptions for as low as $0.90 per dose

Get started

How K Health Can Help 

K Health provides a simple, accessible option for ED treatment. Chat with a doctor on your phone to determine whether you are experiencing ED. Your doctor will then prescribe you medication, which can be picked up at a local pharmacy or shipped discreetly directly to you. They will also provide a longer-term care plan to help you manage your ED.

Frequently Asked Questions

How can I get the maximum effect from Cialis?
Taking Cialis as recommended by your doctor is the best way to experience the medication’s maximum effect. If you’re taking it as a daily medication, be sure to take Cialis at the same time every day. If you’re taking Cialis as needed, don’t take more than one dose per day. When taking Cialis, reduce alcohol and grapefruit consumption to avoid unwanted side effects.
How long does Cialis last?
Cialis can last in your system for up to 36 hours. In the treatment of erectile dysfunction (ED), it can help men become erect at any time during that window, so long as they are sexually aroused.
How long does it take for Cialis to work?
It usually takes about 30 minutes for Cialis to work in the treatment of ED, but it can take up to two hours to take effect in some men.
What can I take to enhance Cialis?
Unless your doctor tells you otherwise, you shouldn’t take anything in addition to Cialis to enhance its effects.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Chesney Fowler, MD

Dr. Fowler is an emergency medicine physician and received her MD from George Washington University. She completed her residency in emergency medicine at Christiana Care Health System. In addition to her work at K Health, Dr. Fowler is a practicing emergency medicine physician in Washington, DC.