Cialis (tadalafil) is a prescription drug used to treat erectile dysfunction and benign prostatic hyperplasia. Cialis can cause side effects that range from mild to serious. Examples include headache and upset stomach.

Specifically, Cialis is used in adults to treat:

Depending on the condition you’re taking Cialis to treat, your doctor may have you take it only when you need it or once daily.

The active ingredient in Cialis is tadalafil. (An active ingredient is what makes a drug work.) The drug comes as a tablet that you swallow.

Keep reading to learn about the common, mild, and serious side effects that Cialis can cause. For a general overview of the drug, including details about its uses, see this article.

Some people may experience mild to serious side effects during their Cialis treatment.

Examples of the drug’s commonly reported side effects include:

* To learn more about this side effect, see the “Side effects explained” section below.

Many side effects of Cialis are mild and go away on their own after a few days or weeks.

Examples of mild side effects that have been reported with this drug include:

* To learn more about this side effect, see the “Side effects explained” section below.

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking Cialis unless your doctor recommends it.

Cialis may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

It’s possible to have serious side effects from Cialis, but they were rare in the drug’s studies.

Serious side effects that have been reported with Cialis include:

If you develop serious side effects while taking Cialis, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about this side effect, see the “Side effects explained” section below.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Cialis, visit MedWatch.

Get answers to some frequently asked questions about side effects of Cialis.

Does my risk of side effects with Cialis depend on the dose I take (such as 5 mg vs. 20 mg)?

It’s possible. Many side effects of Cialis are the same regardless of which dose you take. But your risk of some side effects may be higher with a Cialis dose of 20 milligrams (mg) versus 5 mg.

For example, in Cialis studies, certain side effects were reported more often by people taking 20 mg than by those taking the 5-mg dose. These included:

  • headache
  • upset stomach
  • back pain

For more details about the difference in side effects based on dosage, see the drug’s prescribing information. You can also refer to this article for details about Cialis dosages.

Does Cialis cause any long-term side effects?

Yes. Although it’s rare, Cialis may cause long-term side effects. These include side effects that can start after you’ve been taking the drug for a long time or after your treatment ends. And they may continue for a long time, regardless of when they begin.

Examples of long-term side effects that may occur with Cialis include:

  • hearing loss
  • vision loss
  • tissue damage caused by a prolonged erection*

These side effects were rarely reported in the drug’s studies. But if you have concerns about potential long-term side effects with Cialis, talk with your doctor.

* To learn more about this side effect, see the “Side effects explained” section below.

Are certain side effects more common if I take Cialis daily?

Not really. Many common side effects of Cialis are the same whether you take the drug daily or as needed. (See “What are the more common side effects of Cialis?” above for more information.)

How do the side effects of Cialis and Viagra compare?

Many common side effects of Cialis are the same as common side effects of Viagra. Both drugs are used to treat erectile dysfunction in adult males.* (Unlike Viagra, Cialis is also approved to treat benign prostatic hyperplasia, which is enlargement of the prostate gland.)

Examples of side effects that are common with both drugs include:

A common side effect reported in studies of people taking Viagra but not Cialis is abnormal vision. But it’s important to note that there have been eye-related side effects reported with Cialis since it came on the market. And there is a risk of a serious eye condition called non-arteritic anterior ischemic optic neuropathy (NAION)‡ with both Cialis and Viagra.

On the other hand, a common side effect reported by people taking Cialis in studies was pain in the arms and legs. This side effect was not reported by people who took Viagra.

The following side effects can happen with both Cialis and Viagra, but are more common with Viagra:

It’s also possible to have serious side effects from either Cialis or Viagra. These side effects are the same for both drugs and include:

  • vision loss
  • hearing loss
  • prolonged erection†
  • high or low blood pressure†

Talk with your doctor or pharmacist if you have questions about the potential side effects of Cialis or Viagra.

* In this article, we use the term “male” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.
† To learn more about this side effect, see the “Side effects explained” section below.
‡ NAION is a condition that can cause damage to the optic nerve, which is responsible for your vision.

How do the side effects of Cialis compare with those of the generic version?

The generic version of Cialis is tadalafil, which is also the active ingredient in Cialis. (An active ingredient is what makes a drug work.) Because tadalafil contains an exact copy of the active drug in Cialis, the side effects for both drugs are the same.

To learn more about the side effects of tadalafil, see the drug’s prescribing information.

Learn more about some of the side effects Cialis may cause.

Headache

It’s possible to have headaches while taking Cialis. This was one of the more common side effects reported in the drug’s studies.

Cialis can cause headaches because it works by widening your blood vessels, which increases blood flow. And widening of the blood vessels in your head may cause headaches.

Headache can also be a symptom of high or low blood pressure, both of which are rare but serious side effects of Cialis.

Drinking alcohol while taking Cialis may also increase your risk of headaches. (For more details, see “Alcohol and Cialis” in the “Warnings” section below.)

What might help

Most headaches caused by Cialis are mild and go away after a few hours or days. Over-the-counter (OTC) pain relievers, such as ibuprofen (Advil, Motrin) or acetaminophen (Tylenol), may help relieve your headache. But you should always talk with your doctor or pharmacist before taking any OTC drugs. They’ll let you know whether they’re safe to take with Cialis or your condition.

If you have bothersome headaches that don’t go away, let your doctor know. They’ll likely check your blood pressure and do other examinations to try to determine the cause. And if you drink alcohol, talk with your doctor to learn how much, if any, is safe to consume while taking Cialis.

High or low blood pressure

Taking Cialis can cause changes in your blood pressure, such as causing high or low blood pressure. In the drug’s studies, low blood pressure was more common than high blood pressure.

Symptoms of low blood pressure can include:

Your risk of low blood pressure with Cialis is higher if you take other drugs that lower your blood pressure.

High blood pressure was rarely reported in the drug’s studies, but it can happen. You likely won’t have symptoms with mild high blood pressure. But severe high blood pressure may cause symptoms such as:

What might help

Tell your doctor right away if you have symptoms of high or low blood pressure while taking Cialis. They’ll try to determine the cause and provide any necessary treatment.

It’s also important to tell your doctor all the medications you take before you start taking Cialis. They’ll let you know whether this drug is a safe treatment option for you.

Muscle pain

Muscle pain was one of the more common side effects reported in studies of Cialis. It usually happened about 12 to 24 hours after people took their dose of the drug.

In most cases, muscle pain caused by Cialis was mild or moderate and went away on its own within 48 hours. Muscle pain due to Cialis generally affects your lower back, buttock, and thigh muscles. Lying down was reported to worsen the muscle pain.

What might help

Muscle pain caused by Cialis is often mild and usually goes away on its own within 2 days. Talk with your doctor if you have bothersome muscle pain while taking this drug. They may recommend an OTC pain reliever such as ibuprofen (Motrin, Advil) or acetaminophen (Tylenol).

Be sure to talk with your doctor or pharmacist before taking any OTC drugs. They’ll let you know whether they’re safe to take with your treatment or condition.

Prolonged erection

Taking Cialis can cause a prolonged erection that lasts more than 4 hours. Although it’s rare, this side effect is serious and requires medical attention.

A prolonged erection with Cialis may lead to priapism, which is a painful erection that lasts longer than 6 hours. Priapism is a medical emergency that requires immediate treatment. Untreated priapism can cause permanent damage to your penis, including not being able to have an erection at all.

What might help

Call your doctor right away or go to a hospital if you have an erection that lasts longer than 4 hours. It’s important to get immediate treatment for a prolonged erection to avoid permanent penis damage.

Allergic reaction

Like most drugs, Cialis can cause an allergic reaction in some people.

Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, usually in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms. Examples include:

  • an antihistamine you swallow, such as Benadryl (diphenhydramine)
  • a product you apply to your skin, such as hydrocortisone cream

If your doctor confirms you’ve had a mild allergic reaction to Cialis, they’ll decide whether you should continue taking it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Cialis, they may have you switch to a different treatment.

Keeping track of side effects

During your Cialis treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking a new drug or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how it affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Keeping notes and sharing them with your doctor will help them learn more about how Cialis affects you. They can then use this information to adjust your treatment plan if needed.

Cialis may not be right for you if you have certain medical conditions. (This is known as a drug-condition interaction.) Other factors may also affect whether this drug is a good treatment option for you.

Talk with your doctor about your health history before starting Cialis. Factors to consider include those described below.

Heart problems. Sexual activity can affect your heart function. Let your doctor know if you have or have had heart problems, such as a heart attack or irregular heart rhythm. They’ll let you know whether sexual activity is safe for you based on your heart health. Stop any sexual activity and seek immediate medical attention if you have chest pain or an irregular heart rhythm while taking Cialis.

Allergic reaction. If you’ve had an allergic reaction to Cialis or any of its ingredients, your doctor will likely not prescribe it for you. Ask them about other medications that might be better options.

Prolonged erection. Cialis may cause prolonged erections that last longer than 4 hours. If you have a history of prolonged erections, you may have a higher risk of this side effect from Cialis. Certain conditions, including sickle cell anemia, multiple myeloma, and Peyronie’s disease, can also increase your risk of a prolonged erection with Cialis. Be sure to tell your doctor if you have any of these conditions before starting this drug. They’ll let you know whether it’s safe for you.

Hearing problems. It’s possible that Cialis may cause sudden hearing loss or other hearing problems, such as ringing in the ears. If you already have these conditions, this drug may worsen them. Tell your doctor if you have problems with hearing before starting Cialis. They’ll help you decide whether it’s safe for you to take.

Kidney problems. If you have severe kidney problems, your body may not be able to get rid of Cialis as well as it should. This could cause the drug to build up in your system, which may increase your risk of side effects. Let your doctor know if you have kidney problems before starting this drug. They may have you take a lower dose of Cialis.

Liver problems. If you have liver problems, your body may not be able to get rid of Cialis as well as it should. This can increase your risk of side effects from the drug. Tell your doctor if you have liver problems before starting Cialis. Depending on how well your liver works, they may have you take a lower dose of the drug or recommend a different treatment option.

Blood pressure problems. Taking Cialis may cause high or low blood pressure. If you already have problems with your blood pressure, this drug may worsen them. Before starting Cialis, tell your doctor if you have any blood pressure problems and if you take medication to lower your blood pressure. They’ll decide whether Cialis is safe for you.

Pulmonary hypertension. Tell your doctor if you have pulmonary hypertension before starting Cialis. Certain medications used to treat this condition may cause dangerously low blood pressure if taken with Cialis. If you take medication to treat pulmonary hypertension, your doctor may recommend a different treatment than Cialis.

Stroke. Before starting Cialis, tell your doctor if you’ve had a stroke. This drug may increase your risk of stroke. You should not take Cialis if you’ve had a stroke within the past 6 months.

Vision loss or retinitis pigmentosa. Cialis may cause vision problems, including vision loss. If you have a history of vision loss or retinitis pigmentosa, you may have an increased risk of this side effect. Tell your doctor if you’ve had any vision problems before starting Cialis. They’ll help you decide whether this medication is right for you.

Bleeding problems. It’s possible that Cialis may increase your risk of bleeding. If you already have bleeding problems, such as hemophilia or stomach ulcers, Cialis may worsen your condition. Let your doctor know if you have any bleeding problems before starting Cialis. They’ll let you know whether this drug is safe for you to take.

Alcohol and Cialis

Both Cialis and alcohol can lower your blood pressure. So consuming alcohol while taking this drug may increase your risk of having very low blood pressure.

Having five or more drinks* a day while taking this medication could cause a sudden drop in blood pressure when you stand. Symptoms can include:

Due to this risk, it’s recommended that you limit the amount of alcohol you drink while taking Cialis. If you drink, talk with your doctor about how much, if any, is safe to consume with this drug.

* One drink is considered one glass of wine, one beer, or one shot or cocktail.

Pregnancy and breastfeeding while taking Cialis

Cialis is not approved for use in females.* And it’s not known whether this drug is safe to take during pregnancy or while breastfeeding. Talk with your doctor if you have questions about taking Cialis during pregnancy or while breastfeeding.

* In this article, we use the term “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Most side effects of Cialis are mild and go away on their own after a few hours or days. Although it’s rare, some people may have serious side effects from this drug.

Talk with your doctor to learn what to expect with Cialis and how to manage any side effects that may occur. Here are a few examples of questions you may want to ask:

  • Is my risk of low blood pressure higher when I first start treatment with Cialis?
  • Does my risk of prolonged erection depend on the dose I take?
  • Do I have an increased risk of side effects if I’m age 65 years or older?
  • Does Cialis cause hair loss?

To learn more about Cialis, see these articles:

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Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.