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Blood Tests for Leukemia: What To Expect

Medically reviewed by Mark Levin, M.D. — Written by Victoria Menard
Posted on June 10, 2021
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When To Use Blood Tests | What To Expect | Types of Blood Tests | Members’ Tips | Support

Leukemia is a cancer of the blood cells that begins in the bone marrow. It is often first diagnosed when routine blood tests show abnormal results. As one MyLeukemiaTeam member wrote, their chronic leukemia was diagnosed “through a regular yearly blood test.”

Blood tests are not only used to confirm a diagnosis of leukemia — they may also be used throughout leukemia treatment to give your doctors better insight into how your body is functioning and responding to treatment. This article describes what to expect when undergoing blood tests for leukemia.

When Are Blood Tests Used for Leukemia?

Blood tests for leukemia may be used to diagnose cancer and to track your health and progress during treatment. These lab tests are sometimes used in conjunction with a bone marrow biopsy or bone marrow aspiration, in which a sample of the spongy tissue or fluid found in some bones is taken for laboratory analysis.

Leukemia is often discovered before symptoms arise when routine blood tests return abnormal results. Having abnormal levels of white blood cells, red blood cells, or platelets may indicate that a person has leukemia. In some types of leukemia, cancer cells may appear in the blood. In other types, however, leukemia cells remain in the bone marrow for some time, making them undetectable in blood tests.

If you have leukemia, blood tests may also be used during treatment to monitor the number of different types of blood cells in your body, find indicators of cancer activity, and measure chemicals in the body that indicate overall health and organ functioning.

How Are Blood Tests for Leukemia Performed?

Your doctor may ask for a blood sample through a finger prick or a blood draw, usually done by inserting a needle into a vein, most often in the inner elbow. This blood is then sent to a laboratory for analysis.

A hematologist (a specialist who studies blood) may ask you to follow special instructions, such as fasting (not eating or drinking) for a certain amount of time before your blood test. The frequency of your blood testing depends on what the sample is being used for and your doctor’s recommendations. As one MyLeukemiaTeam member shared, “I take a blood test once a week.”

Types of Blood Tests for Leukemia

Many different types of blood tests can be used to diagnose leukemia and track your health and progress throughout treatment. Here are some of the most commonly used tests.

Complete Blood Count

A complete blood count (CBC) shows the current number of cells in your blood and what types of cells they are. Leukemia and treatments for leukemia, such as chemotherapy and radiation, can affect circulating blood cell counts in various ways. A CBC can be used to help diagnose leukemia, track progress during treatment, and determine whether leukemia has spread (metastasized) to the bone marrow.

A white cell differential (also called a CBC plus differential) may also be performed during a CBC to determine your body’s ability to fight infections. A differential can be done using a manual count, but it is usually performed automatically by a cell counter.

You may find that changes in your leukemia symptoms coincide with changes in your blood counts. As one MyLeukemiaTeam member wrote, “I get really tired and weak when my blood counts drop.”

Learn more about understanding blood counts in leukemia.

Peripheral Blood Smear

A peripheral blood smear (also called a smear), also known as a manual differential (diff), may be recommended if your CBC results are inconclusive or abnormal. During a blood smear, a smeared drop of blood is examined under a microscope. A specialist determines whether the blood sample contains abnormal cells and whether normal blood cells appear in the usual proportions.

Changes in the shape, size, or number of cells may suggest leukemia. The presence of immature white blood cells (called lymphoblasts or blasts) may also indicate that a person has leukemia.

Minimal Residual Disease

Minimal residual disease (MRD) is a relatively new type of test used in blood cancers that can detect small numbers of cancer cells — even one malignant cell in 1 million normal cells — that may remain after leukemia treatment.

Three main types of tests measure minimal residual disease. Testing methods vary by type of cancer and may involve blood or bone marrow samples.

Flow Cytometry and Immunophenotyping

Flow cytometry identifies cancer cells by finding protein markers on the cell surface. This testing can find one cancer cell in 100,000 normal cells. Results from flow cytometry have a quick turnaround, often less than one day.

Used to identify specific characteristics of leukemia cells, immunophenotyping is another tool that allows doctors to understand exactly what type of leukemia you have and which treatments are likely to work best.

Polymerase Chain Reaction

Polymerase chain reaction (PCR) may be performed with a blood sample or a bone marrow sample. This test looks for DNA specific to leukemia cells and can identify one cancer cell in 100,000 to 1 million normal cells. It may take several weeks to find out the results of this test.

Next-Generation Sequencing

Next-generation sequencing (NGS) is a faster way to examine the genetic material (DNA or RNA) of cells. NGS generally requires a bone marrow sample. In some cases, however, it may be possible to test a blood sample for cancerous DNA.

Results from NGS may be available within one week. So far, the U.S. Food and Drug Administration (FDA) has approved NGS tests only for use in B-cell acute lymphoblastic leukemia (B-cell ALL).

Blood Chemistry

An analysis of your blood chemistry does not assess blood cells, but rather substances in the blood, such as proteins, hormones, vitamins, and electrolytes. Blood chemistry results can indicate the severity of leukemia, as well as how well organs such as the kidneys or liver are functioning. These tests are not used to diagnose leukemia.

Cytogenetic Analysis

Cancer is the result of genetic mutations in specific cells. Researchers have identified a wide variety of genetic variants associated with subtypes of cancer. Identifying these genetic variants helps doctors predict the course of the disease and which treatments are most likely to be effective.

Cytogenetic testing of leukemic cells analyzes changes to the chromosomes or genes. Cytogenetic testing is an important part of leukemia diagnosis. It can also be used to determine the best treatment approaches and monitor your response to treatments.

Karyotype Test

A karyotype test looks at the number and appearance of the chromosomes in cancer cells to determine specific abnormalities. Karyotyping provides further details that may be used to create a tailored treatment plan.

Molecular Profiling

In some people with leukemia, indicators of cancer, called biomarkers, circulate in the blood. These biomarkers can also be associated with how well a person is responding to their cancer treatments. Molecular profiling can be used to identify these biomarkers and develop a highly individualized treatment plan.

Along with PCR and NGS, the following tests may be performed as part of molecular profiling.

Fluorescence in Situ Hybridization

Fluorescence in situ hybridization (FISH) can identify genetic changes to blood cancer cells in samples of blood or bone marrow. FISH may be used during diagnosis to help select the best treatment plan. During treatment, FISH may be performed every three to six months to monitor the effectiveness of treatment.


Immunohistochemistry may be used alongside flow cytometry and genetic testing to diagnose leukemia. It may also be used to identify the type of leukemia a person has. This method involves using antibodies to test for the presence of antigens — foreign substances that cause the body to produce an immune response.

Blood Coagulation Tests

In people with leukemia, the blood may occasionally have an increased tendency to clot (hypercoagulability). As the name suggests, coagulation tests can be performed to determine whether the blood is clotting normally.

MyLeukemiaTeam Members on Blood Tests for Leukemia

Many MyLeukemiaTeam members have shared their experiences with blood tests. Some have offered their tips for handling these tests.

Many members advise taking the time to understand the results of your bloodwork and asking questions. “Today’s lesson,” wrote one member: “I always get a copy of my bloodwork. I sit down later and compare every test. I would recommend everyone do that.”

Some members find that keeping a positive attitude helps make blood testing easier. As one member shared, “Blood test again today … my numbers have been rising for a bit. I’m hoping things level off … I will see! Until I get bad news, it’s good news for now!”

Meet Your Team

Life with leukemia can pose many challenges. The good news is that you don’t have to face them alone.

MyLeukemiaTeam is the social network for people with leukemia and their loved ones. Here, members from across the world come together to ask questions, offer support and advice, and share stories of their everyday lives with leukemia.

Want to add to the conversation? Share your thoughts and experiences in the comments below or by posting on MyLeukemiaTeam.

Posted on June 10, 2021
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Mark Levin, M.D. is a hematology and oncology specialist with over 37 years of experience in internal medicine. Review provided by VeriMed Healthcare Network. Learn more about him here.
Victoria Menard is a writer at MyHealthTeam. Learn more about her here.

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