A person’s blood count refers to the number of red blood cells, white blood cells, and platelets in their blood. When the counts of these blood components decrease below the normal range, it is called a low blood count or cytopenia. There are several potential causes of low blood counts, ranging from lifestyle factors and medication side effects to serious medical conditions that affect blood cell production in the bone marrow.
What is a complete blood count?
A complete blood count (CBC) is a common blood test that provides important information about the kinds and numbers of cells in the blood. It measures:
- Red blood cells – Cells that carry oxygen to tissues in the body.
- White blood cells – Cells that help fight infection.
- Platelets – Cell fragments that help form blood clots.
The CBC provides counts for each of these components and also checks:
- Hemoglobin – The protein in red blood cells that carries oxygen.
- Hematocrit – The proportion of blood that is made up of red blood cells.
Doctors order CBC tests routinely to screen for low blood counts and other abnormalities. When blood counts are lower than normal, it may indicate an underlying problem.
What are the normal ranges for blood counts?
The normal reference ranges for blood counts in adults are:
- Red blood cells:
- Men: 4.7 to 6.1 million cells/microliter
- Women: 4.2 to 5.4 million cells/microliter
- Hemoglobin:
- Men: 13.5 to 17.5 grams/deciliter
- Women: 12.0 to 15.5 grams/deciliter
- Hematocrit:
- Men: 40.7% to 50.3%
- Women: 36.1% to 44.3%
- White blood cells: 4,500 to 11,000 cells/microliter
- Platelets: 150,000 to 450,000 platelets/microliter
These ranges may vary slightly between laboratories. Counts outside the normal range could signify low blood counts.
What is anemia?
Anemia is a condition that develops when the blood lacks enough healthy red blood cells and hemoglobin. It is the most common blood disorder. There are over 400 types of anemia, which are categorized by their causes:
- Anemia caused by blood loss – Losing blood from heavy periods or internal bleeding can lead to anemia.
- Anemia caused by decreased or faulty red blood cell production – This can occur from deficiencies in iron, vitamin B12, folate, or other nutrients needed to produce red blood cells. It can also be caused by bone marrow or stem cell disorders.
- Anemia caused by destruction of red blood cells – Certain diseases, infections, autoimmune disorders, and inherited conditions can damage red blood cells and lead to anemia.
The most common symptom of anemia is fatigue. Headaches, dizziness, pale skin, chest pain, cold hands and feet can also occur. Treatment depends on the underlying cause.
What is leukopenia?
Leukopenia refers to a low white blood cell count below 4,500 cells/microliter. White blood cells, also called leukocytes, are vital for the immune system to defend the body against infection. The main types are:
- Neutrophils – Fight bacterial infections
- Lymphocytes – Fight viral infections and cancers
- Monocytes – Consume and remove dead cells
- Eosinophils – Respond to allergies and parasites
- Basophils – Play a role in inflammatory responses
Having a shortage of one or more types of white blood cells raises the risk of infections. Leukopenia can be inherited or acquired. Causes include:
- Autoimmune disorders
- Bone marrow damage
- Cancers like leukemia and lymphoma
- HIV/AIDS
- Medications, such as chemotherapy drugs
- Radiation exposure
- Sepsis
- Viral infections
Treatment aims to address the underlying cause and prevent infections.
What is thrombocytopenia?
Thrombocytopenia refers to a low platelet count below 150,000 platelets/microliter. Platelets are cell fragments that circulate in the blood and stick together to form clots and stop bleeding. A shortage of platelets is called thrombocytopenia. It can lead to:
- Easy or excessive bruising
- Prolonged bleeding from cuts
- Nosebleeds and bleeding gums
- Abnormally heavy menstrual periods
- Blood in urine or stool
Some potential causes of low platelet counts include:
- Autoimmune disorders
- Bone marrow disorders
- Cancers and leukemia
- Enlarged spleen
- Viral infections like HIV or hepatitis C
- Pregnancy
- Medications
- Alcohol abuse
Doctors determine the cause to guide treatment. In mild cases, no treatment may be needed. For low counts, platelet transfusions or medications may be given.
What lifestyle factors affect blood counts?
Certain lifestyle factors influence blood cell counts and can contribute to low counts if unchecked. These include:
Poor diet and malnutrition
Consuming a diet low in iron, vitamin B12, folate and other nutrients can impair the bone marrow’s ability to produce blood cells. This nutritional deficiency leads to lower cell counts over time.
Alcohol abuse
Drinking excessive amounts of alcohol suppresses the bone marrow and interferes with blood cell production. It also causes vitamin and mineral deficiencies. Low blood counts are common in people with alcoholism.
Smoking
Smoking increases the risk of blood cancers like leukemia and myelodysplastic syndromes. It also releases toxins that can damage bone marrow function. Smokers tend to have lower blood cell counts.
Sedentary lifestyle
Lack of physical activity is associated with lower hemoglobin concentrations and red blood cell counts. Even mild-to-moderate exercise helps boost hemoglobin levels.
Obesity
Excess body fat may impair red blood cell production and limit the bone marrow’s capacity to generate new blood cells. Obesity also increases inflammation which can impact blood counts.
Chronic stress
Prolonged stress raises levels of the hormone cortisol, which can slow the production of red blood cells, white blood cells and platelets when elevated over long periods. Managing stress is important.
Making lifestyle adjustments like eating a balanced diet, exercising regularly, losing weight and limiting alcohol intake can help optimize blood cell counts.
How do medications affect blood cell counts?
A number of prescription and over-the-counter medications can adversely affect blood cell counts:
- Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen may lead to reduced platelets.
- Blood thinners like warfarin and heparin can cause thrombocytopenia.
- Antibiotics, including sulfonamides and penicillins, may cause leukopenia or thrombocytopenia.
- Anticonvulsants like phenytoin are associated with low blood counts.
- Antifungals and antivirals can suppress bone marrow activity.
- Anti-hypertensives like captopril may rarely cause agranulocytosis, a severe lack of neutrophils.
- Chemotherapy drugs work by killing cells, including blood cells. They often dramatically lower counts.
The prescribing doctor should monitor blood counts regularly in patients on these medications. Stopping the drug usually allows counts to recover.
What infections reduce blood cell counts?
Many bacterial, viral, fungal and parasitic infections affect blood counts:
- Sepsis – A severe bacterial infection of the blood that causes cytopenias.
- HIV – Progresses to AIDS as the virus destroys white blood cells called CD4 T cells.
- Hepatitis – Liver inflammation can impair production of blood cells.
- Influenza – The flu virus can attack bone marrow cells.
- Epstein-Barr virus – Causes mononucleosis leading to enlarged spleen and low blood counts.
- Parvovirus B19 – Results in fifth disease, temporarily stopping red blood cell production.
- Cytomegalovirus – Herpesvirus that may induce thrombocytopenia.
- Dengue fever – Viral infection sometimes causing leukopenia and thrombocytopenia.
Treating the underlying infection can help restore normal blood counts. Severely low counts may require transfusions or hematopoietic growth factors.
What cancers lead to low blood counts?
Many cancers, especially blood cancers like leukemia and lymphoma, directly impair the bone marrow’s ability to produce healthy blood cells. Other cancers like breast and lung cancer can also infiltrate or crowd the bone marrow. Cancer treatments like chemotherapy and radiation therapy are also very toxic to blood cell precursors. Common cancers associated with cytopenias include:
- Leukemia – Cancer of the early white blood cells.
- Lymphoma – Cancer involving lymphocytes.
- Multiple myeloma – Cancer of plasma cells in the bone marrow.
- Myelodysplastic syndromes – Abnormal bone marrow cell production.
- Aplastic anemia – Bone marrow failure.
- Breast cancer – Advanced breast cancer spreads to the bone marrow.
- Lung cancer – Lung tumors can metastasize to the bone marrow.
Doctors treat the underlying malignancy, but medications to boost blood counts, transfusions and bone marrow transplantation may be necessary to manage cytopenias.
What autoimmune diseases lead to low blood counts?
Autoimmune disorders involve the immune system attacking the body’s own healthy cells. They are a relatively common cause of cytopenias. Examples include:
- Rheumatoid arthritis – Associated with anemia and thrombocytopenia.
- Lupus – Can cause hemolytic anemia, leukopenia and thrombocytopenia.
- Inflammatory bowel disease – Anemia often occurs in Crohn’s disease and ulcerative colitis.
- Autoimmune hemolytic anemia – Immune destruction of red blood cells causes anemia.
- Immune thrombocytopenic purpura (ITP) – Antibodies target and destroy platelets.
- Felty’s syndrome – Complication of rheumatoid arthritis causing cytopenias.
- Large granular lymphocytic leukemia – Rare leukemia leading to neutropenia.
Treatment centers on suppressing the overactive immune response using corticosteroids, intravenous immunoglobulin, immunosuppressants and monoclonal antibodies.
When are transfusions used to treat low blood counts?
Blood transfusions can rapidly restore blood counts in severe symptomatic cytopenias or when levels decline dangerously low.
Criteria for a red blood cell transfusion usually include hemoglobin less than:
- 7 g/dL in stable, non-bleeding patients
- 8 g/dL in stable patients with cardiovascular disease
- 10 g/dL in actively bleeding patients
Platelet transfusions may be appropriate when counts fall below:
- 10,000/microliter with risk of bleeding
- 50,000/microliter before surgery
- 20,000/microliter in those with active bleeding
For life-threatening neutropenia, granulocyte transfusions from donors may help raise neutrophil counts.
Transfusions come with risks like allergic reactions and blood-borne infections. Doctors weigh these risks against the need for urgent treatment.
When are hematopoietic growth factors used?
Hematopoietic growth factors are medications used to stimulate blood cell production in certain cytopenias:
- Erythropoietin (EPO) – Treats anemia in chronic kidney disease and chemotherapy-induced anemia.
- Granulocyte colony-stimulating factor (G-CSF) – Used for neutropenia from chemotherapy or bone marrow failure.
- Thrombopoietin receptor agonists – Treat chronic ITP and thrombocytopenia in chronic liver disease or chemotherapy.
These agents promote proliferation and maturation of blood cell precursors in the bone marrow. They can raise counts and reduce requirements for transfusions.
What tests help diagnose the cause of low blood counts?
Doctors use various tests to determine the underlying reason for abnormal blood counts:
- Complete blood count – Confirms low counts and provides details about which cell lines are affected.
- Peripheral blood smear – Allows examination of blood cells under the microscope for abnormalities in shape, size and appearance.
- Reticulocyte count – Measures immature red blood cells released by the bone marrow, useful for classifying anemia.
- Vitamin and mineral tests – Check for deficiencies in iron, folate, B12, etc.
- Bone marrow biopsy – Takes a marrow sample to assess cellularity and rule out cancers like leukemia.
- Genetic testing – Identifies inherited disorders affecting blood cells.
- Imaging tests like CT scans help check for enlarged spleen or cancers.
- Immune function tests aid diagnosis of autoimmune cytopenias.
Identifying the specific cause of the low blood count directs treatment to resolve the underlying problem.
Summary
Blood counts outside the normal range indicate deficiencies in red blood cells, white blood cells and/or platelets. Many diseases, lifestyle factors, cancers, autoimmune disorders, infections, medications and inherited conditions can impair blood cell production and lead to cytopenias.
Doctors diagnose the specific cause through blood tests, bone marrow biopsies, genetic testing, imaging and other studies. Treatment aims to address the underlying condition and may involve transfusions, growth factors, medications, or lifestyle changes. Restoring normal blood counts is essential to oxygen delivery, prevent infections, and stop bleeding problems.