If you have type 2 diabetes, your doctor might suggest Actos (pioglitazone) as a treatment option for you. Along with other questions you may have about the drug, you could be wondering about its side effects.

Actos is a prescription medication that’s used to treat type 2 diabetes in adults.* It’s used along with diet and exercise to help manage blood sugar levels.

Actos comes as a tablet that you’ll swallow. It’s typically used as a long-term treatment. For more information about Actos, see this in-depth article on the drug.

Like other drugs, Actos can cause mild or serious side effects (also called adverse effects). Keep reading to learn more.

* Actos isn’t approved to treat type 1 diabetes.

Some people may experience mild or serious side effects during their Actos treatment.

Examples of commonly reported side effects of Actos include:

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

Keep reading to learn about other possible mild and serious side effects of Actos.

Some people may have mild side effects while taking Actos.

Examples of mild side effects that have been reported with Actos 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, too. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist. And don’t stop using Actos unless your doctor recommends it.

Actos may cause mild side effects other than the ones listed above. See the Actos prescribing information for details.

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 Actos, visit MedWatch.

In rare cases, serious side effects can occur with Actos.

Serious side effects that have been reported with Actos include:

* Actos has a boxed warning for this side effect. This is the most serious warning from the Food and Drug Administration (FDA). To learn more, see the “Side effects explained” section below.
† An allergic reaction is possible after using Actos. But this side effect wasn’t reported in studies. To learn more about this side effect, see the “Side effects explained” section below.

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

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

Do side effects of Actos vary depending on whether I take the drug on its own or with metformin?

Yes, it’s possible for side effects to vary depending on whether you take Actos with metformin.

Your doctor may prescribe Actos along with other diabetes drugs to help manage your blood sugar level. In studies, Actos was prescribed in combination with metformin (Fortamet, Glumetza, Riomet), insulin, or sulfonylureas, such as glimepiride (Amaryl) and glipizide (Glucotrol).

When Actos is used with metformin,* most side effects of Actos are typically the same as when Actos is used by itself. But metformin commonly causes digestive problems, such as nausea, vomiting, constipation, and diarrhea. So you may experience these side effects if you take Actos with metformin.

For a list of side effects that may occur when Actos is taken with metformin, see the prescribing information for Actos. You can also talk with your doctor or pharmacist.

* Pioglitazone, the active drug in Actos, is available together with metformin as a generic drug and as the brand-name drug ActoPlus MET. For details on this drug combination, including possible side effects, see this this article.

Does my risk of side effects from Actos depend on the strength I take (15 mg, 30 mg, or 45 mg)?

Yes. Certain side effects of Actos are dose-dependent, meaning your risk of these side effects is greater at higher doses.

In studies of Actos, weight gain* and swelling were more likely to occur at higher doses of the drug.

If you have other questions about what to expect with Actos based on the strength you’re prescribed, talk with your doctor or pharmacist.

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

Will I need to have any lab tests to monitor for side effects of Actos?

Yes, it’s possible you may need lab tests to monitor for side effects of Actos.

In rare cases, taking Actos may lead to liver problems, such as liver failure. If you have liver problems before taking the drug, you may have a higher risk of this side effect.

Before you start treatment with Actos, your doctor will give you liver function tests. If your test results show you have liver disease, your doctor will let you know if it’s safe for you to take Actos.

If your doctor says it’s safe to take Actos, they’ll regularly check your liver function while you’re taking the drug. They may have you stop taking the drug if your liver function worsens over time.

To learn more about getting lab tests to monitor for side effects of Actos, talk with your doctor.

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

Weight gain

Weight gain is a common side effect of Actos.

Weight gain can be caused by swelling, which is another possible side effect of Actos. Swelling from Actos usually happens in your feet, ankles, or lower legs.

Keep in mind that swelling and rapid weight gain can be symptoms of congestive heart failure (CHF). Rapid weight gain is defined as gaining more than 2 to 3 pounds in 24 hours or more than 5 pounds in 1 week. CHF is a possible serious side effect of Actos. To learn more, see “Congestive heart failure” right below.

What might help

If you’re concerned about weight gain with Actos, talk with your doctor. They can suggest ways to maintain a healthy weight.

If you notice swelling or rapid weight gain while taking the drug, tell your doctor right away. They can check for other symptoms of heart failure and discuss a treatment plan.

Congestive heart failure

Actos has a boxed warning for new or worsening congestive heart failure (CHF). A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

With CHF, your heart doesn’t pump blood to the rest of your body as effectively as it should.

In studies of Actos, CHF was a rare side effect. CHF can happen when you take the drug by itself or with other diabetes drugs. But your risk of CHF with Actos may be higher if you take the drug together with insulin.

Possible symptoms of CHF include:

  • rapid weight gain (defined as gaining more than 2 to 3 pounds in 24 hours or more than 5 pounds in 1 week)
  • swelling, especially in your feet, ankles, or lower legs
  • shortness of breath
  • increased heart rate
  • confusion or trouble thinking

What might help

If you have symptoms of CHF, tell your doctor right away. It’s recommended that you avoid taking Actos if you have CHF with symptoms.

You shouldn’t take Actos if you have class 3 or class 4 heart failure. (These are types of serious heart failure.) Based on the type of heart failure you have, your doctor can tell you if Actos is right for you.

Infections

Infections are a common side effect of Actos. Infections that were reported in studies of Actos include sinus infections, upper respiratory infections, and urinary tract infections. The common cold is an example of an upper respiratory infection.

Symptoms will vary based on the specific infection you may have. But possible symptoms include:

What might help

If you have symptoms of an infection while taking Actos, talk with your doctor. They can suggest ways to manage your symptoms. They can also advise if treatments are available for the specific infection you have.

Allergic reaction

Like most drugs, Actos can cause an allergic reaction in some people. But this side effect wasn’t reported in studies.

Symptoms can be mild or serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically 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. To manage your symptoms, they may suggest an over-the-counter antihistamine you take by mouth, such as Benadryl (diphenhydramine). Or they may recommend a product you apply to skin, such as hydrocortisone cream.

If your doctor confirms you had a mild allergic reaction to Actos, they’ll decide if you should continue using 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 had a serious allergic reaction to Actos, they may have you switch to a different treatment.

Keeping track of side effects

During your Actos treatment, consider keeping notes on any side effects you’re having. Then, you can share this information with your doctor. This is especially helpful to do when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

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

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

In certain situations, it may not be safe to take Actos. Read on to learn more about possible warnings for Actos.

Boxed warning: Congestive heart failure

Actos has a boxed warning for congestive heart failure (CHF). A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

Taking Actos may lead to new or worsening CHF. It’s recommended that you avoid taking Actos if you have CHF with symptoms. You shouldn’t take Actos if you have class 3 or class 4 heart failure. (These are types of serious heart failure.)

To learn more, see the “Side effects explained” section above.

Other warnings

Actos may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Actos. The list below includes factors to consider.

Bladder cancer. In rare cases, Actos may cause bladder cancer. If you currently have bladder cancer, be sure to tell your doctor before starting Actos treatment. They’ll likely prescribe a drug other than Actos for you.

Liver problems. Rarely, taking Actos may lead to liver problems, such as liver failure. If you have liver problems before taking the drug, you may have a higher risk of this side effect. Your doctor will monitor your liver function closely while you take Actos. Or they may prescribe a treatment other than Actos for your condition.

Osteoporosis. If you have osteoporosis, be sure to tell your doctor before you start taking Actos. Actos may cause broken bones, especially in the arms and legs. You may have a higher risk of this side effect if you have osteoporosis. Your doctor can advise if it’s safe for you to take Actos.

Allergic reaction. If you’ve had an allergic reaction to Actos or any of its ingredients, you shouldn’t take Actos. Ask your doctor what other medications are better options for you.

Irregular periods. Actos can cause ovulation, which raises your risk of pregnancy. This effect can occur in females* who don’t normally have ovulation as part of their menstrual cycle. Before you start taking Actos, be sure to tell your doctor if you have irregular periods. They may recommend that you use effective birth control while taking the drug.

* 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.

Alcohol use and Actos

There aren’t known safety issues with drinking alcohol while taking Actos.

But keep in mind that alcohol can affect your blood sugar levels. Actos is used to help manage blood sugar levels in people who have type 2 diabetes. So you may need to limit the amount of alcohol you drink while taking the drug.

If you drink alcohol, talk with your doctor about the amount that’s safe for you to consume while taking Actos.

Pregnancy and breastfeeding while taking Actos

It isn’t known if Actos is safe to take during pregnancy or while breastfeeding.

If you’re pregnant or breastfeeding, or planning to become pregnant or breastfeed, talk with your doctor before starting Actos treatment.

Actos is used to treat type 2 diabetes. You may have mild side effects while taking the drug. In rare cases, you may experience serious side effects, such as bladder cancer.

If you have questions about side effects from Actos, talk with your doctor or pharmacist. Below are a few questions you may want to ask:

  • How can I maintain a healthy weight while taking Actos?
  • Do I have a higher risk of any side effects of Actos?
  • Will other drugs I’m taking raise my risk of side effects from Actos?

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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.