If you have a certain type of cancer that affects your blood cells, your doctor might suggest Venclexta (venetoclax) as a treatment option. Learning about the possible side effects of Venclexta may help you and your doctor decide to add it to your treatment plan.

Venclexta is a prescription medication. It’s used as a long-term treatment for the following conditions in adults:

Venclexta comes as a tablet that you take by mouth once daily with food and water.

For more information about Venclexta, including details about its uses, see this in-depth article on the drug.

Like other drugs, Venclexta can cause mild or serious side effects. Keep reading to learn more.

Some people may experience mild or serious side effects during their Venclexta treatment. These side effects can vary depending on what condition the drug is being used to treat.

More common side effects in people taking Venclexta for chronic lymphocytic leukemia or small lymphocytic lymphoma include:

In people taking Venclexta for acute myeloid leukemia, more common side effects include:

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

Taking Venclexta may cause mild side effects in some people. These side effects can vary depending on the condition you’re using the drug to treat. Examples of mild side effects that have been reported with Venclexta 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 Venclexta unless your doctor recommends it.

Venclexta may cause mild side effects other than the ones listed above. See the Venclexta 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 Venclexta, visit MedWatch.

Less commonly, serious side effects have occurred in some people who took Venclexta. These include:

* To learn more about this side effect, see the “Side effects explained” section below.
† An allergic reaction is possible after using Venclexta. But this side effect wasn’t reported in studies.

If you develop serious side effects while taking Venclexta, 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.

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

Fluid buildup in your body

Fluid buildup in your body, also known as edema, is a common side effect of Venclexta. Fluid may collect in various areas of the body and cause swelling. Fluid buildup from Venclexta most commonly causes swelling of the legs, arms, feet, and hands.

In studies of people who took Venclexta for acute myeloid leukemia, fluid buildup caused swelling in several parts of the body. In some people, fluid buildup or swelling was reported in their legs, arms, hands, feet, eyelids and area around the eyes, face, or penis.

Symptoms of fluid buildup may include:

  • swelling and puffiness
  • stiffness or pain
  • pitting, which occurs when your finger leaves a dent in your skin after pressing on it for a few seconds
  • bruising or discoloration
  • trouble putting on socks or shoes
  • weight changes

What might help

Treatment of fluid buildup depends on how severe the swelling is and what areas of your body are affected.

You may be able to ease swelling by placing a cold compress on the affected areas for a few minutes at a time. When possible, try to elevate the swollen area above heart level. For example, prop your legs up on pillows while you’re sitting or resting.

Limiting sodium in your diet can help to ease fluid buildup. Being physically active and exercising also helps.

If your symptoms of this side effect become bothersome or severe, tell your doctor. They may suggest treatments, such as diuretics, to relieve this side effect, especially if you have certain health conditions.

Low blood cell levels

Taking Venclexta can lower the levels of certain cells in your blood. These include white blood cells, platelets (also called thrombocytes), and red blood cells.

In studies, low blood cell levels commonly occurred in people taking Venclexta. The symptoms of this side effect depend on which types of blood cells have low levels.

Neutropenia (low levels of neutrophils, a type of white blood cell) is common while taking Venclexta. This increases your risk of infections because white blood cells fight off pathogens (germs) that cause infections. General symptoms of an infection can include fever, chills, body aches, and cough. If you develop infection symptoms while taking Venclexta, tell your doctor right away.

Thrombocytopenia (low platelet levels) are also common while taking Venclexta. If you don’t have enough platelets in your body, your blood won’t be able to clot (stop bleeding) after an injury. Symptoms can include bruising or bleeding easily, nosebleeds, coughing up blood, and blood in your urine, stool, or vomit.

Anemia (low red blood cell levels) can occur while taking Venclexta. Red blood cells carry oxygen throughout your body. A typical symptom of anemia is fatigue (low energy).

What might help

Blood cell levels (also called blood cell counts) are measured using a blood test called a complete blood count (CBC). Your doctor will likely test your CBC regularly while you’re taking Venclexta.

If you develop symptoms of low blood cell levels, you should let your doctor know right away. Don’t wait to see if your symptoms go away on their own.

If your doctor confirms that your blood cell levels are low, they may have you pause or stop taking Venclexta. They may also prescribe certain medications or supplements to help treat or prevent low blood cell levels.

If you have questions about your risk of low blood cell levels, talk with your doctor or pharmacist.

Nausea

In studies, nausea was one of the most common side effects reported in people taking Venclexta. It’s a common side effect of many types of medications used to treat cancer.

Nausea can cause vomiting and lead to dehydration.

What might help

It’s important to always take Venclexta with plenty of water. Continue to drink water throughout each day to keep your body hydrated.

If you develop nausea that becomes severe or doesn’t go away, tell your doctor. If you’re dehydrated due to vomiting, they may suggest medical care. This might include giving you fluids intravenously (through a vein). They may also prescribe an anti-nausea medication, such as Zofran (ondansetron).

Allergic reaction

Like most drugs, Venclexta 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 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 your skin, such as hydrocortisone cream.

If your doctor confirms you had a mild allergic reaction to Venclexta, 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 Venclexta, they may have you switch to a different treatment.

Keeping track of side effects

During your Venclexta 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 Venclexta affects you. And your doctor can use this information to adjust your treatment plan if needed.

Venclexta 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 Venclexta. The list below includes factors to consider.

Infections. Treatment with Venclexta increases the risk of serious infections, such as pneumonia. If you currently have an infection, it should be treated before you start Venclexta. Before taking Venclexta, talk with your doctor about any viral, bacterial, fungal, or other infections you may have.

Liver or kidney problems. People with liver or kidney problems may be more likely to develop certain side effects with Venclexta. This is because the liver and kidneys help break down medications, such as Venclexta, and remove them from your body. Problems with these organs may lead to slowed drug removal and increased side effects. If you have liver problems, your doctor may prescribe a lower dose of Venclexta. And if you have any liver or kidney problems, they may also monitor you more closely for side effects during treatment.

High blood levels of calcium, phosphorous, potassium, or uric acid. Venclexta can cause a serious side effect called tumor lysis syndrome (TLS). TLS occurs when cancer cells break down rapidly and release chemicals into your blood. These chemicals include calcium, phosphorous, potassium, and uric acid. If you already have high levels of these substances in your blood, tell your doctor. They’ll likely use blood tests to monitor you more carefully while you take Venclexta. And they may prescribe treatments to bring these levels down before you start taking it.

Allergic reaction. If you’ve had an allergic reaction to Venclexta or any of its ingredients, you should not take this drug. Ask your doctor what other medications are better options for you.

Alcohol use and Venclexta

Alcohol shouldn’t interact with Venclexta.

But alcohol and Venclexta can cause some of the same side effects, such as nausea. Combining alcohol and the drug could possibly make nausea or other side effects worse.

If you drink alcohol, it’s a good idea to ask your doctor about how much is safe for you to drink while taking Venclexta.

Pregnancy and breastfeeding while taking Venclexta

Venclexta use is not recommended during pregnancy. It isn’t known for sure, but taking the drug while pregnant may be harmful to a fetus.

Because of this risk, it’s recommended that females* use birth control while taking Venclexta. And they should continue using birth control for at least 30 days after their last dose of the drug.

Tell your doctor if you’re pregnant or planning to become pregnant before you start taking Venclexta. If you become pregnant during treatment, tell your doctor right away.

It is not known if Venclexta is safe to use while breastfeeding. It also isn’t known if the drug passes into breast milk or affects a breastfed child. It’s recommended that you avoid breastfeeding during treatment and for at least 1 week after your last dose.

If you’re breastfeeding or planning to breastfeed, talk with your doctor. They may recommend other ways to feed your child while you take Venclexta.

* 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.

Venclexta is an effective treatment for certain types of cancer. Like most drugs, Venclexta can cause side effects in some people. If you’re considering the drug as a treatment option, it’s useful to learn about its possible side effects.

If you have questions about your risk of side effects from Venclexta, talk with your doctor. Here are some questions to get you started:

  • Do Venclexta’s side effects vary depending on the tablet strength (10 mg, 50 mg, or 100 mg)?
  • Will receiving vaccines while taking Venclexta increase my risk of side effects?
  • Do my other medications and health conditions raise my risk of side effects from Venclexta?
  • Is it safe to skip doses of Venclexta treatment if I want to avoid side effects for a weekend trip or special event?

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.