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Low blood cell counts

When the bone marrow doesn’t make normal numbers of blood cells it is called bone marrow suppression or myelosuppression. Having bone marrow suppression can cause low blood cell counts, which means lower levels of one or more types of blood cells. The bone marrow is the spongy tissue in the centre of the bones. It is where red blood cells (RBCs), white blood cells (WBCs) and platelets are made.

Each type of blood cell lives for a certain amount of time. When blood cells die, they are normally replaced by new ones made in the bone marrow.

Lifespan of blood cells
Type of blood cellsLifespan

red blood cells (RBCs)

about 120 days

white blood cells (WBCs)

about 6–8 hours


about 7–10 days

Some cancer treatments, including chemotherapy and radiation therapy, can affect the bone marrow so it doesn’t make normal numbers of blood cells. When the bone marrow doesn’t work properly, blood cells are not replaced as they normally would be and blood cell counts drop. Blood cell counts usually start to drop 7–10 days or longer after treatment. The time frame depends on the type of treatment given.

The lowest level that blood cell counts reach is called the nadir. Each type of blood cell has a different nadir and, each type’s nadir occurs at different times. Because RBCs live the longest, it takes them longer to reach their nadir. WBCs and platelets reach their lowest levels about 7–14 days after treatment. Symptoms of low blood cell counts are often worse at nadir. Blood cell counts often begin to recover and rise on their own, usually 2–4 weeks after treatment.

Low blood cell counts can cause delays in treatment, changes in treatment and unscheduled trips to the hospital. Your healthcare team will frequently check your blood cell counts.


Low blood cell counts can be caused by the cancer itself or its treatments.

Cancer cells in the bone marrow

Blood-related cancers, such as leukemia or multiple myeloma, affect blood cells in the bone marrow. Lymphoma and some solid tumours can spread to the bone marrow and affect blood cell production.


Chemotherapy can damage tissues in the bone marrow that make blood cells. People with kidney or liver problems have a higher risk of low blood cell counts while on chemotherapy because their bodies can’t break down the chemotherapy drugs.

Radiation therapy

Radiation therapy can damage tissues in the bone marrow that make blood cells. This is especially true if areas that contain large amounts of bone marrow, such as the pelvic bones, are treated with radiation.

Major surgery

It isn’t clear why major surgery to remove tumours affects the bone marrow. It may be related to lowered immune function after surgery or anesthesia.

Biological therapy

Biological therapy can affect the bone marrow in a similar way to chemotherapy drugs.


Symptoms of low blood cell counts can vary depending on their cause and other factors. It can also vary with the type of blood cell that is affected.

A low red blood cell count is called anemia. It can cause:

  • fatigue
  • pale skin, lips or nail beds
  • increased heart rate
  • tiring easily with exertion
  • dizziness
  • shortness of breath
  • headache
  • irritability – more often seen in young children

A low white blood cell count is called neutropenia or leukopenia. It can cause:

  • a greater risk of infection
  • fever and chills if an infection is present

A low platelet count is called thrombocytopenia. It can cause:

  • easy bruising
  • bleeding from the nose, gums or mouth
  • tiny red spots on the skin, or petechiae
  • blood in the urine
  • dark or black bowel movements

Pancytopenia refers to low levels of all 3 types of blood cells. The symptoms could include any or all of the above symptoms.


Your doctor will try to find the cause of low blood cell counts. You may need to have the following tests.

A complete blood count (CBC) measures the levels of blood cells. It is done before treatment starts to provide a baseline to compare blood test results done during and after treatment. CBCs are often done throughout treatment to check for low blood cell counts.

Bone marrow aspiration and biopsy is a procedure in which a small amount of bone marrow and bone is removed and looked at under a microscope. This test may be done to find the cause of low blood cell counts if they are low for a long period of time.

Managing low blood cell counts

Once the cause of low blood cell counts is known, your healthcare team can develop a treatment plan. A low blood cell count is managed based on the type of blood cell affected. Some people need medicines or blood transfusions to treat severe problems caused by low blood cell counts.

In general, the following measures can help prevent complications of low blood cell counts:

  • Avoid strenuous activity, contact sports and heavy lifting.
  • Avoid forceful coughing.
  • Blow the nose gently.
  • Follow food safety guidelines to reduce the chance of contaminating food.
  • Avoid raw vegetables and other foods with rough surfaces.
  • Eat high-protein foods.
  • Practise good mouth care.
  • Drink plenty of fluids.
  • Thoroughly wash all cuts and scratches.
  • Avoid contact with people who are unwell or have a contagious disease.
  • Get plenty of rest.
  • Avoid crowds whenever possible.