• Complete blood count (CBC) is a common blood test often performed for people living with leukemia.
• If a CBC shows high or low numbers of any type of blood cell, this can help doctors better understand how leukemia and its treatment affect the body.
• Some types of abnormal blood counts may come with symptoms, but test results usually are the only sign something is amiss.

People living with leukemia need numerous blood tests before, during, and after treatment. When you give a blood sample, it may be tested in the laboratory in many different ways. Common blood tests for leukemia include complete blood count, genetic analysis of cancer cells, and minimal residual disease (MRD) — a measurement of how many leukemia cells remain in the body after treatment.

A CBC is one of the most frequently run tests in people with leukemia. The abbreviations that appear on a CBC results report can be confusing. Here’s a breakdown of what this test looks for and what the results can tell doctors.

Types of Blood Cells

A complete blood count shows the current number of cells in your blood and their types. Blood is made of three main types of cells:

• Red blood cells (RBCs) — Also referred to as erythrocytes, their primary function is to carry oxygen from the heart and lungs to different parts of the body.
• White blood cells (WBCs) — Also known as leukocytes, they work as a first line of defense in the immune system, fighting bacteria and viruses that may enter the blood.
• Platelets — Also referred to as thrombocytes, these small cell fragments gather at sites of injury and help blood clot.

Hematocrit and Hemoglobin

Two other aspects of blood are usually tested in a CBC: hematocrit and hemoglobin. Hematocrit levels measure how much of your blood, by percentage, is currently made up of red cells. Hemoglobin measures the amount of oxygen carrying protein inside your red blood cells. Knowing your hematocrit and hemoglobin levels helps doctors better understand how well red blood cells are carrying oxygen to the tissues of your body.

Normal Ranges for Blood Count Results

On a CBC, levels of red blood cells, white blood cells, and platelets are typically expressed as the number of cells per microliter of blood. Normal blood counts vary by individual. However, there are general ranges for certain groups of people.

According to the Leukemia & Lymphoma Society, the normal range of red blood cells per microliter is:

• 4.7 million to 6.1 million for men
• 4.2 million to 5.4 million for women
• 4 million to 5.5 million for children

The normal range of white blood cells per microliter is:

• 5,000 to 10,000 for men
• 4,500 to 11,000 for women
• 5,000 to 10,000 for children

Normal ranges for hematocrit levels are:

• 42 percent to 52 percent of total blood count for men
• 37 percent to 47 percent for women
• 32 percent to 44 percent for children

Hemoglobin is expressed in grams per deciliter. Normal ranges for hemoglobin are:

• 14 to 18 for men
• 12 to 16 for women
• 9.5 to 15.5 for children

Platelet counts are considered normal at 150,000 to 400,000 per microliter for everyone.

White blood cells are also measured by the ratio of types — the WBC differential. There are five main types of white blood cells: neutrophils, eosinophils, lymphocytes, monocytes, and basophils. In a normal blood count, the WBC differential of an adult consists of:

• 55 percent to 70 percent neutrophils
• 20 percent to 40 percent lymphocytes
• 2 percent to 8 percent monocytes

Basophils and eosinophils make up the remainder.

Abnormal Blood Count Results

Leukemia can affect blood cell counts in various ways, as can many cancer treatments, including chemotherapy and radiation.

What do abnormal results mean? For any given value, a result can be too high, too low, or unusual in relation to another value. For instance, the WBC differential may show an abnormal skew in the white blood cell types.

Abnormal results can indicate an issue in the bone marrow — where blood cells are made — or a variety of other disease processes. Although normal ranges are an expression of what is normal for most healthy people, those with underlying conditions may have lower or higher ranges that are normal for them. For instance, in people living with heart disease, a higher-than-normal RBC count may be normal.

Your CBC results will help your doctor better understand how your leukemia and treatments are affecting your body. If results show your risk of serious side effects or complications is rising, your doctor may make a change in your leukemia treatment or prescribe other medications.

Anemia

A person who has a low RBC, hematocrit, or hemoglobin count is considered anemic. Anemia may occur when the bone marrow makes too few red blood cells or when a disease is destroying them. Anemia can also result from low levels of iron, vitamin B12, or folate in the diet or from potential causes such as heavy or persistent bleeding. In leukemia, anemia may develop when the abnormal leukemic cells divide uncontrollably, taking over the bone marrow and preventing the production of normal blood cells.

If your RBC, hematocrit, or hemoglobin count is low, your doctor may order a follow-up blood test called a reticulocyte count. Reticulocytes are immature red blood cells. Counting them can help determine whether the problem is reduced RBC production or if the cells are being destroyed.

High Red Blood Cell Count

High RBC levels may mean there’s not enough oxygen in the blood and can also indicate dehydration. In rare cases, a high RBC count may be due to polycythemia vera, a type of blood cancer in which the bone marrow makes too many red blood cells. Overly high RBC counts are treated by drawing blood until the count is lowered. In some cases, medication might be used to reduce the amount of red cells.

Low Platelet Count

A low platelet count, also referred to as thrombocytopenia, can indicate potential problems with blood clotting. Thrombocytopenia may occur when the bone marrow makes too few platelets or platelets are being destroyed. In some cases, the body doesn’t recognize its own platelets and attacks them. In chronic lymphocytic leukemia (CLL), proteins called antibodies attack and destroy platelets and red blood cells.

A blood transfusion is the most treatment for low platelets, but your doctor may suggest other methods to reduce the chance of bleeding. If a blood test shows your platelets are low, your doctor may recommend avoiding common nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin, naproxen, and ibuprofen. These medications can interfere with the blood's ability to clot.

High Platelet Count

A high platelet count is called thrombocytosis. The two most common causes are a preexisting condition and a bone marrow abnormality. Thrombocytosis is treated with medications that inhibit platelet production in bone marrow.

Low White Blood Cell Count

An overall low white blood cell count, also called leukopenia, means the body’s ability to fight infection is impaired. Having fewer neutrophils in WBC counts is called neutropenia. When neutrophils are low, normal symptoms of infection may not show up because they’re specifically caused by the reaction of neutrophils when fighting infection.

Lymphocytes are the first cells that react to viruses, so low levels mean the body can’t detect or fight viral infection as easily as usual.

Both leukemia and leukemia treatments can cause leukopenia.

High White Blood Cell Count

Also known as leukocytosis, a high WBC count is a hallmark of some types of leukemia and other cancers of the bone marrow. High WBC counts can also indicate an existing infection or a dysfunction in the immune system.

Pancytopenia

Low levels of red blood cells, white blood cells, and platelets (all three) is called pancytopenia. This condition can be caused by leukemia or other bone marrow diseases, a side effect of chemotherapy or radiation treatment, an autoimmune condition, or an infection.

Symptoms of Abnormal Blood Counts

Your test results may be the only sign of an abnormal blood count. However, different symptoms may be linked with different low or high blood cell counts — for example:

• Anemia may cause fatigue, weakness, shortness of breath, and pale skin.
• Low platelet count can cause easy bruising, excessive bleeding from minor cuts and scrapes, or bleeding from the nose or gums.
• High platelet counts can lead to stroke, heart attack, or a dangerous blood clot.
• Low white blood cell count can lead to infections that may cause fever, cough, white patches in the mouth, problems urinating, and diarrhea, among many other potential symptoms of infection.

Can Blood Counts Indicate Different Types of Leukemia?

Different types of leukemia can be indicated by different blood test results. Acute lymphocytic leukemia may cause a large number of lymphoblasts (immature white cells) in the blood, as well as low numbers of red blood cells and platelets. Acute myeloid leukemia may cause pancytopenia. In both CLL and small lymphocytic lymphoma and chronic myeloid leukemia, mature cell counts are closer to normal, resulting in less severe symptoms than occur with acute leukemias.

Talk With Others Who Understand

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