Side effects are possible with most medications, and Cialis is no exception. It’s important to understand potential side effects so you know what to watch for. It’s also important to separate fact from fiction.

This guide reviews Cialis side effects, including potential common, mild, and serious side effects. It also covers what to do about them, including when to talk with your doctor.

Cialis® (tadalafil) is an FDA-approved medication used to treat erectile dysfunction (ED) and benign prostatic hyperplasia (BPH). It’s available as the generic medication tadalafil, which is the same active ingredient in Cialis. Tadalafil is typically less expensive than brand-name Cialis, and is considered equally safe and effective. 

Cialis side effects

Cialis side effects and tadalafil side effects are expected to be the same. Side effects discussed below apply to both brand-name Cialis and generic tadalafil. Remember, tadalafil is the active ingredient in Cialis, so it isn’t surprising that they have the same side effects.

Most common side effects of tadalafil

According to clinical studies, the most common side effects of Cialis are:

• Headache
• Indigestion
• Back pain
• Muscle pain or aches
• Flushing
• Runny or stuffy nose

In most cases, these side effects go away on their own within a few hours. For example, back or muscle pain is most likely about 12 to 24 hours after taking Cialis, and symptoms typically go away within two days.

Let your healthcare professional know if you have tadalafil side effects that linger or bother you. They can help determine if your symptoms need medical care.

Mild side effects of tadalafil

Side effects of Cialis vary slightly depending on how it's used and what condition you’re taking it to treat.

For treating erectile dysfunction, Cialis can be taken as-needed or once daily without timing your dose around sex. The table below compares mild tadalafil side effects based on whether it was taken as-needed or once daily in clinical studies:

As you can see, mild Cialis side effects are similar regardless of whether you take it as-needed or once daily. But there are a few differences.

Serious side effects of tadalafil

Serious side effects of Cialis are possible, but they aren’t common. Having certain medical conditions may raise your risk, so be sure to tell your doctor about your complete medical history before taking Cialis.

Hearing changes

A sudden decrease or loss of hearing has been rarely reported as a tadalafil side effect. Hearing changes are rare enough that it isn’t clear whether this side effect is due to Cialis or is caused by other factors.

If you experience dizziness or ringing in your ears, any degree of hearing loss, immediately stop taking Cialis and call your healthcare professional for medical advice.

Priapism

Priapism refers to a prolonged (four hours or more), often painful erection that occurs without sexual stimulation. This is a rare side effect any PDE5 inhibitor, including Cialis, may cause.

You should seek immediate medical care if you have a painful erection that lasts more than four hours after taking Cialis. Priapism is an emergency that needs medicare attention as soon as possible.

There are risk factors that increase your risk for a prolonged erection as a Cialis side effect. These factors include:

• Sickle cell anemia
• Multiple myeloma
• Leukemia
• Peyronie’s disease or other anatomical problem with the penis

Heart-related side effects

Heart-related side effects are possible with Cialis, but context here is important.

Before prescribing Cialis, your healthcare professional should evaluate whether your heart is healthy enough for sexual activity. Sex can trigger heart-related events including heart attack in people with certain medical conditions, especially heart disease and other heart problems. Due to this risk, using Cialis is not recommended in certain situations. Talk with your healthcare professional to learn more about whether your heart is healthy enough to take Cialis.

Cialis can also cause a temporary drop in blood pressure after you take a dose. In most people, this drop is so small you likely won’t notice. However, the drop can be noticeable in rare cases.

Eye and vision-related side effects

Tadalafil side effects include changes to your color vision. You may have trouble distinguishing between green and blue, or you may see a blue shade to objects. Blurry vision is also possible. These are often temporary and go away within a few hours after taking a dose.

Another Cialis side effect is non-arteritic anterior ischemic optic neuropathy (NAION). Non-arteritic anterior ischemic optic neuropathy (NAION) can cause a decrease or even total loss of vision that may be permanent. This is extremely rare, though.

Immediately stop using Cialis and seek medical care if you have a sudden loss of vision in one or both eyes.

Allergic Reaction

You should not take Cialis (tadalafil) if you’ve had an allergic reaction to it in the past. You also shouldn’t take it if you’ve had an allergic reaction to other medications that contain tadalafil, such as Adcirca. 

Taking tadalafil again may cause another allergic reaction. Instead, your healthcare professional can prescribe a different PDE5 inhibitor for you to try.

Long-term side effects of tadalafil

They’re not common, but long-term side effects are possible with tadalafil.

Sudden vision loss can happen and may be permanent in extreme cases. However, this is very rare.

Priapism (a prolonged erection that’s often painful) is another Cialis side effect. Without immediate medical care, priapism can cause long-term consequences including damage to the penis and a permanent inability to get an erection.

Talk with your healthcare professional if you have questions or need medical advice on your risks for long-term side effects of tadalafil.

Cialis vs. Viagra side effects

Cialis (tadalafil) and Viagra® (sildenafil) are both FDA-approved ED medications. They’re both prescription drugs that aren’t available over-the-counter. They work in the same way. So, it makes sense that Cialis and Viagra have very similar side effects.

Cialis vs. Viagra common side effects

The table below compares and contrasts the most common Cialis side effects versus the most common Viagra side effects. These are based on reports from Viagra clinical trials and Cialis clinical trials.

Cialis vs. Viagra mild side effects

Cialis and Viagra cause similar mild side effects, as detailed in the table below.

Cialis vs. Viagra serious side effects

Serious side effects aren’t common with Cialis or Viagra, but they can happen. Serious side effects reported with both Cialis and Viagra include:

• Allergic reaction
• Eye and vision-related side effects that can be permanent, including vision loss in one or both eyes
• Hearing changes, including sudden hearing loss
• Priapism
• Heart-related side effects, which typically affect men with a pre-existing heart condition

If you’d like to know more about how Cialis and Viagra compare, talk with your doctor or pharmacist.

How to reduce side effects of tadalafil

Side effects are frustrating, so it’s normal to wonder how to reduce side effects of Cialis (tadalafil).

Talk with your doctor

The best way to reduce side effects is to prevent them from happening. Before you start taking Cialis, tell your healthcare professional about all medications you take, including any supplements or over-the-counter medications. You should also tell them about any other medical conditions you have or had in the past. Certain medical conditions, such as heart disease, can raise your risk for tadalafil side effects.

If you have side effects while using Cialis, let your doctor know. Many Cialis side effects are related to the dose. So your doctor may lower your dosage to see if this makes your side effects go away.

Avoid Cialis drug interactions

Certain medications and health conditions can increase your risk for side effects of tadalafil. These interactions vary in severity. Some medications should not be used with Cialis, and some medical conditions make taking the drug at any dosage unsafe. In other cases, your doctor may want to prescribe a lower Cialis dosage due to an interaction.

Examples of medications that interact with Cialis include:

• Certain antifungal drugs, including ketoconazole and itraconazole
• Certain antibiotic drugs, including erythromycin
• Nitrates, including nitroglycerin and isosorbide mononitrate, as well as recreational “poppers” such as amyl nitrite
• Riociguat (Adempas)
• Other medications that block phosphodiesterase type 5 (PDE 5 inhibitors), including medications used to treat pulmonary arterial hypertension such as Revatio (sildenafil) or Adcirca (tadalafil)
• Alpha blockers, such as doxazosin or tamsulosin
• Blood pressure medications, including lisinopril, metoprolol, and amlodipine

Only take Cialis as prescribed

Finally, always take Cialis exactly as your healthcare provider prescribes. Do not take a higher dose than recommended. Avoid taking more than one dose of Cialis over a 24-hour period. And don’t hesitate to reach out to your doctor if you have questions about how to safely take Cialis.

When to talk with your doctor

You should talk with your doctor if you develop mild side effects that last more than a few hours or days. You should also reach out to your healthcare professional if your side effects bother or interrupt your daily activities.