Chronic Lymphocytic Leukemia


What is chronic lymphocytic leukemia?

Chronic lymphocytic leukemia (CLL) is a type of blood and bone marrow cancer.

What is bone marrow?

Bone marrow is the spongy tissue inside your bones. This tissue contains stem cells, which produce blood cells.

How does chronic lymphocytic leukemia affect my body?

Typically, the stem cells in your bone marrow produce two types of blood stem cells: myeloid stem cells and lymphoid stem cells.

Myeloid stem cells become one of three types of blood cells:

  • Platelets, which create blood clots to stop bleeding.
  • Red blood cells, which carry oxygen to the rest of the body.
  • White blood cells, which fight infection.

Lymphoid stem cells become one of three types of lymphocytes (white blood cells):

  • B lymphocytes: These cells create antibodies, cells that protect you from infection.
  • T lymphocytes: T lymphocytes aid B lymphocytes in creating antibodies.
  • Natural killer cells: These cells attack cancer and other viruses.

When you have CLL, your body creates abnormal lymphocytes, or leukemia cells. These cells do not fight infection very well. As the number of abnormal cells grows, your body has less room for healthy red blood cells, white blood cells and platelets.

Who might get chronic lymphocytic leukemia?

CLL is most common in adults. Usually, people develop the disease during middle age or later. Most people who receive a CLL diagnosis are around age 70. The disease rarely affects children.

How common is chronic lymphocytic leukemia?

In the United States, around 20,000 new cases of CLL occur annually. Chronic lymphocytic leukemia is one of the most common types of leukemia in adults. It accounts for about 1 in 4 new leukemia cases.

Symptoms and Causes

What causes chronic lymphocytic leukemia?

Experts do not know the cause of chronic lymphocytic leukemia.

What are the symptoms of chronic lymphocytic leukemia?

You may not have any symptoms of CLL. It’s often found because of an abnormal blood test result.

Check with your healthcare provider if you experience:

Diagnosis and Tests

How is chronic lymphocytic leukemia diagnosed?

The first step in diagnosing chronic lymphocytic leukemia is a physical exam. Your healthcare provider will ask you questions about your symptoms. Your provider will also check for signs of disease, such as new or unusual lumps.

What tests might I have for chronic lymphocytic leukemia?

Healthcare providers may use tests that examine blood, bone marrow or lymph nodes. These tests include:

  • Bone marrow tests: Healthcare providers can often diagnose CLL through blood tests. However, bone marrow tests provide more information about how advanced CLL is. Healthcare providers may analyze a small bone marrow sample through bone marrow aspiration and biopsy.
  • Complete blood count (CBC) with differential: A complete blood count measures the number of red blood cells, white blood cells and platelets in your blood. It also assesses how much hemoglobin (protein that carries oxygen) your red blood cells have.
  • Flow cytometry: This test can determine whether the lymphocytes in your blood contain CLL cells. With flow cytometry, healthcare providers take a small blood sample to analyze in a laboratory.
  • Genetic tests: Healthcare providers use gene tests to examine chromosomes and DNA (genetic code) that can detect CLL. Examples of these tests include fluorescent in situ hybridization (FISH) and immunoglobulin heavy chain (IGHV) tests.

Management and Treatment

How is chronic lymphocytic leukemia treated?

Your treatment plan depends on how advanced CLL is. If CLL is in early stages, healthcare providers may opt for a “watchful waiting” approach.

If your symptoms are more severe, CLL treatment may include:

What medications are used for chronic lymphocytic leukemia?

Healthcare providers may also prescribe medication or infusion therapy for CLL, such as:

  • BCL2 inhibitor therapy: This medicine blocks BCL2, a protein found on leukemia cells. This treatment can destroy leukemia cells or make them more sensitive to other cancer drugs.
  • Monoclonal antibody therapy: Healthcare providers create monoclonal antibodies in a lab. These antibodies attach to cancer cells. The antibodies block cancer cells’ growth or destroy the cells. Examples of monoclonal antibody therapy medications include rituximab (Rituxan®), ofatumumab (Arzerra®) or obinutuzumab (Gazyva®).
  • Tyrosine kinase inhibitor (TKI) therapy: This treatment blocks the enzymes that cause stem cells to develop into excess white blood cells. Examples of TKIs include ibrutinib (Imbruvica®), acalabrutinib (Calquence®), idelalisib (Zydelig®) and duvelisib (Copiktra®).


How can I reduce my risk for chronic lymphocytic leukemia?

There is no known way to prevent CLL. You can lower your risk of developing diseases like cancer by making healthy choices, including:

  • Eating a diet full of fruits, vegetables and whole grains.
  • Exercising regularly.
  • Maintaining a healthy weight.
  • Managing stress.
  • Sleeping enough.

Outlook / Prognosis

What is the outlook for people with chronic lymphocytic leukemia?

Many people with chronic lymphocytic leukemia go long periods without experiencing symptoms or health complications. People may have treatment for CLL on and off for many years. CLL never goes away, but people can still live a full life with the disease.

Does chronic lymphocytic leukemia return after treatment?

Chronic lymphocytic leukemia can return after treatment. Patients need routine follow-up care to make sure CLL does not return.

Living With

What else should I ask my healthcare provider about chronic lymphotic leukemia?

You may consider asking your healthcare provider:

  • How can I lower my risk of developing CLL?
  • What are the treatment options for CLL?
  • What lifestyle changes should I make if I have CLL?
  • What are the symptoms that my CLL has returned after treatment?
  • What are the signs that I need to call my healthcare provider?

A note from Cleveland Clinic

Chronic lymphocytic leukemia is the most common type of leukemia in adults. It affects your blood cells and bone marrow. You are more likely to get CLL later in life — most people who receive a CLL diagnosis are in their 70s. CLL has several treatment options. Many people who receive treatment experience long periods without CLL symptoms or health complications. If you have chronic lymphocytic leukemia, it’s important to visit your healthcare provider regularly.

Last reviewed by a Cleveland Clinic medical professional on 04/22/2021.


  • American Cancer Society. Chronic Lymphocytic Leukemia. ( Accessed 4/28/2021.
  • Leukemia & Lymphoma Society. Chronic lymphocytic leukemia (CLL). ( Accessed 4/28/2021.
  • National Cancer Institute. Chronic Lymphocytic Leukemia Treatment (PDQ®) – Patient Version. ( Accessed 4/28/2021.

Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy