Venetoclax

Say it: ven-ET-oh-klax · Brand names: Venclexta

Venetoclax is a targeted pill that removes a protein that keeps some blood cancer cells alive, so the cancer cells die.

What it is

Cells have a built-in self-destruct program. Some blood cancer cells make too much of a protein called BCL-2 (B-cell lymphoma 2) that turns this program off. Venetoclax blocks BCL-2, which lets the cancer cells die.

Often used for

• chronic lymphocytic leukemia (CLL)
• small lymphocytic lymphoma (SLL)
• acute myeloid leukemia (AML), along with other medicines

How you get it

Venetoclax is a tablet you take by mouth once a day with a meal. The dose starts low and goes up step by step, over about 5 weeks for chronic lymphocytic leukemia or a few days for acute myeloid leukemia, to keep you safe. For CLL it is often taken for a set time, such as 1 or 2 years. Your schedule may be different.

Common side effects and what helps

• Low white blood cells, which raise the risk of infection. Your team will check your blood often.
• Diarrhea. Drink plenty of fluids and tell your team if it does not get better.
• Nausea. Eat small meals and ask about anti-nausea medicine.
• Low red blood cells or platelets, which can cause tiredness or bruising.
• Cold symptoms or cough. Wash your hands often.
• Feeling tired. Rest and short walks can help.
• Swelling in the legs or feet. Raise your legs when you sit.

Call your care team right away if you have

• A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, or chills
• Little or no urine, muscle cramps or spasms, a fast or uneven heartbeat, or a seizure, which can be signs of tumor lysis syndrome
• Vomiting or diarrhea that will not stop, or you cannot keep fluids down
• Unusual bleeding or bruising
• Cough, shortness of breath, or burning when you urinate

Before you start, tell your team

• If you have kidney problems or high uric acid levels
• If you have liver problems
• If you are due for any vaccines, since live vaccines should be avoided
• If you are pregnant, may become pregnant, or are breastfeeding
• All the medicines you take, including vitamins, herbs and supplements

Good to know

• When cancer cells die quickly, they release their contents into the blood. This is called tumor lysis syndrome and can harm the kidneys and heart. You will drink extra fluids, take medicine to lower uric acid, and have blood tests, and some people stay in the hospital at first.
• Many medicines, including some antifungal and antibiotic medicines, can raise venetoclax levels a lot. Check with your team before starting anything new.
• You will have frequent blood tests to check your blood counts and blood salts.
• Do not get live vaccines before, during or after treatment until your team says it is okay.

At home

• Take it once a day with a meal and water, at about the same time each day.
• Swallow tablets whole. Do not chew, crush or break them.
• Drink plenty of water, about 6 to 8 glasses a day, especially in the first weeks and starting 2 days before each dose increase, unless your team tells you otherwise.
• Avoid grapefruit, Seville oranges (often in marmalade) and starfruit.
• If you miss a dose, ask your care team what to do. Do not take two doses to make up for it.
• Store tablets in their original package, at room temperature, away from children.

Questions to ask

• What is my dose ramp-up schedule?
• How much water should I drink each day?
• Will I need to stay in the hospital at the start?
• Which of my other medicines could interact with it?

Side effect guides

• Fatigue (tiredness)
• Nausea and vomiting
• Diarrhea
• Low white blood cells and infection risk
• Anemia (low red blood cells)
• Low platelets and bleeding
• Cough

Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.