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Leukemia is a cancer that starts in the bone marrow, the soft tissue inside bones where blood cells are made. It causes the body to produce large numbers of abnormal blood cells, usually white blood cells. These abnormal cells do not work properly and crowd out healthy blood cells, which can affect your body’s ability to fight infections, carry oxygen, and stop bleeding.
There are many types of leukemia, which are grouped by how quickly they grow and the kind of blood cell affected. Some leukemias grow quickly (called acute), while others grow more slowly (called chronic). Leukemia can affect adults and children, with some types more common in children and others more common in adults.
Leukemia affects the blood and bone marrow, which are vital for your overall health. Because abnormal cells crowd out healthy ones, leukemia can cause symptoms like feeling very tired, easy bruising or bleeding, infections, weight loss, and night sweats. Early diagnosis and treatment are important to control the disease and improve quality of life.
Treatment aims to slow or stop the growth of leukemia cells and to achieve remission, where signs and symptoms reduce or disappear. Treatments vary depending on the type of leukemia and may include chemotherapy, targeted drugs that attack cancer cells more precisely, radiation therapy, immunotherapy, and sometimes bone marrow or stem cell transplants.
People with leukemia may notice symptoms such as fatigue, fever, unexplained weight loss, night sweats, easy bruising or bleeding, and pain or a feeling of fullness below the ribs. Some types of leukemia, especially chronic forms, may not cause symptoms at first and are found during routine blood tests.
Doctors use a combination of physical exams, medical history, blood tests (like complete blood counts), bone marrow tests, and genetic tests to diagnose leukemia and understand its type. Additional tests may check if the leukemia has spread.
Diagnosis often involves blood tests to look for abnormal cells and bone marrow tests to examine the marrow directly. Genetic tests can identify specific changes in the cancer cells that help guide treatment choices.
Treatment depends on the leukemia type and may include chemotherapy to kill cancer cells, targeted therapy to attack specific cancer cell features, radiation therapy, immunotherapy to boost the immune system, and stem cell or bone marrow transplants to replace damaged marrow. Treatment often happens in phases, starting with induction to achieve remission, followed by post-remission therapy to prevent relapse.
Leukemia is a broad term covering many related diseases, so hearing the word alone does not tell the whole story. Different types have different behaviors, treatments, and outlooks. For example, acute lymphocytic leukemia (ALL) is common in children and grows quickly, while chronic myeloid leukemia (CML) usually grows slowly and may not cause symptoms early on.
It’s important not to assume the same treatment or prognosis applies to all leukemias. Your care team will explain what type you have and what that means for your care.
Patients and caregivers can ask about the specific type of leukemia diagnosed, what tests were done, what treatment options are available, and what side effects to expect. It’s also helpful to ask about the goals of treatment, how remission is defined, and what follow-up care will be needed.
This information is meant to help you understand leukemia but cannot replace advice from your health care provider. If you or a loved one has been diagnosed with leukemia or has symptoms that worry you, the best next step is to talk with your doctor or cancer care team. They can provide personalized information and guide you through diagnosis, treatment, and support.
Public source information used for this glossary entry includes:
Leukemia is a cancer of blood-forming cells that usually begins in the bone marrow and can affect the blood, immune system, and other organs. Its behavior ranges from rapidly progressive acute disease to more chronic patterns, so diagnosis relies on blood tests, marrow evaluation, and molecular markers.