Anemia is a medical condition in which the number of red blood cells (RBCs) – also called the RBC count — or the amount of hemoglobin is less than normal. Hemoglobin is a reddish, iron-containing protein found in red blood cells that gives the red color to blood. Hemoglobin combines with oxygen from the lungs and then transports the oxygen to cells throughout the body. Anemia is the most common blood disease. There are more than 400 different types of anemia, but many of them have different causes, treatments, and outlooks.

Anemia is often treated using blood transfusions, usually from donor blood. More than 44,000 blood donations are performed every day in the United States, and nearly 4.5 million Americans receive a blood transfusion each year. In 2006, an estimated 30 million blood components — including red blood cells and other components — were transfused to patients in the United States.


The incidence of anemia increases with age, particularly after age 65 years. Risk factors associated with the condition include:

  • Patients with diets low in iron, vitamins, or minerals
  • Family history (hereditary factors) that lead to anemia starting at birth.
  • Females of childbearing age (at risk for iron-deficiency anemia due to blood loss during menstruation and increased blood supply needs during pregnancy)
  • Elderly people due to the presence of other health problems and poor diet
  • Strict vegetarians (vegans) who have vitamin deficiencies
  • Long-term alcoholics who have vitamin deficiencies
  • Patients with long-term or serious conditions (kidney disease, cancer, diabetes, rheumatoid arthritis, HIV/AIDS, inflammatory bowel disease, liver disease, heart failure, and thyroid disease
  • Patients with long-term infections


Symptoms of anemiaSymptoms of anemia are usually caused by hypoxia — a reduced amount of oxygen delivered to the cells and tissues of the body. Fatigue is the main complaint of anemia, but some types of the disease, including very mild anemia, have no symptoms. Symptoms may vary from mild to intense and include:

  • Fatigue
  • Decreased energy
  • Weakness
  • Headaches
  • Lightheadedness
  • Cranky attitude
  • Shortness of breath
  • Heart palpitations (sensations of the heart racing or beating irregularly)
  • Pale colored or cold skin
  • Change in stool color (such as black and tarry stools)
  • Rapid heart rate
  • Low blood pressure
  • Rapid breathing
  • Yellowish colored skin (jaundice) if anemia is caused by red blood cell destruction

Symptoms of worsening anemia may include:

  • Problems concentrating or thinking
  • Blue color to the whites of the eyes
  • Brittle nails
  • Coldness in the hands and feet
  • Sore tongue
  • Chest pain, angina, or heart attack
  • Dizziness
  • Fainting or passing out
  • Rapid heart rate

Causes and Types

Anemia is caused by a process involving damage or destruction of red blood cells that results in low hemoglobin levels. The general causes that can lead to anemia include:

  • Certain diseases
  • Certain medications
  • Poor nutrition
  • Blood loss

The types of anemia can be divided into three main groups:

I) Anemia due to blood loss

  • Chronic (long-term) blood loss
  • Acute (blood loss due to sudden onset from surgery,  trauma, or an injury

II) Anemia caused by decreased or impaired red blood cell production

III) Anemia caused by high rates of red blood cell destruction

Anemia may be classified according to the Mean Corposcular Volume (MCV), also known as the mean cell volume. The MCV is a measurement of the average red blood cell size, measured in units of femtoliters (fL), detected in a standard complete blood count. The MCV classification system helps doctors determine the underlying cause of the anemia. A low MCV (less than 80 fL) is called microcytic anemia (low cell volume). An MCV in the normal range (80-99 fL) is considered a normocytic anemia (normal cell volume). A high MCV (above 99 fL) is categorized as a macrocytic anemia (large cell volume).

The World Health Organization (WHO) defines anemia as a hemoglobin level of less than 13 g/dL in men and less than 12 g/dL in women.

Acute anemia is associated with an abrupt drop in hemoglobin to a level of 7-8 g/dL along with symptoms. In chronic anemia, hemoglobin levels of 4-5 g/dL may be tolerated.

All types of anemia can be categorized under the three general groups. Some of the most common forms of anemia are classified, based on the cause of the disease, as follows:

I. Anemia due to blood loss

  • Chronic blood loss

    Slow onset and progression of symptoms

    Iron-deficiency anemia (microcytic, hypochromic anemia) caused by various factors such as:

    – Gastrointestinal conditions (ulcers, hemorrhoids, gastritis (inflammation of the stomach, surgical removal of part of the digestive system, Crohn’s disease)

    – Cancer

    – Use of nonsteroidal anti-inflammatory drugs (NSAIDS) that can lead to ulcers and gastritis

    – Menstruation and childbirth in women

    – Iron-poor diet

    – Certain drugs, foods, and caffeinated beverages

    – Endurance training


  • Acute blood loss (hemorrhagic anemia due to sudden bleeding)

    Abrupt onset and appearance of symptoms

    Acute blood loss anemia occurs when there is a fast and significant blood loss within 1 to 2 days of a sudden major hemorrhage (bleeding) and the bleeding then is controlled.

    A loss of more than 30-40% of the blood volume can trigger shock and possibly death unless the abnormally low blood volume (hypovolemia) is treated appropriately with IV fluids or a blood transfusion.

    Conditions involving acute bleeding with extensive enough blood loss to lead to acute anemia include:

    – Acute hemorrhage due to surgery in patients with pre-exiting chronic conditions such as mesothelioma, other cancers, or other chronic conditions

    – Acute hemorrhage due to trauma

    – Exacerbation of anemia in an anemic patient after blood loss during a surgical operation (such as a hysterectomy) that is unrelated to anemia

    Acute blood loss anemia has a wide range of causes such as:

    – Traumatic injury (damage to the brain)

    – Massive upper or lower gastrointestinal (GI) bleeding hemorrhage

    – Chronic conditions, including cancers such as mesothelioma

    – Chemotherapy for cancer treatment

    – Ruptured ectopic pregnancy

    – Ruptured aneurysm

    – Disseminated intravascular coagulation (DIC) (hrombosis followed by bleeding due to various types of illnesses)

    – Hemoglobinopathy (abnormal hemoglobin production) in severe sickle cell anemia

    – Congenital bleeding disorders (such as Von Willebrand disease and Hemophilia A)

    – Autoimmune hemolytic anemia (impaired RBCs that lead to loss of RBCs in patients with conditions such as lupus, certain types of lymphoma and leukemia

    – Acquired platelet disorder

II. Anemia caused by decreased or impaired red blood cell production

  • Sickle cell anemia

    Sickle cell anemia is an inherited condition that alters the shape and function of red blood cells in some African-Americans and some people of West or Central African black descent. The red blood cells are crescent-shaped, causing them to break down quickly which prevents oxygen from reaching the body’s organs. Severe forms of sickle cell anemia may lead to acute anemia.

  • Thalassemia

    Thalassemia refers to a group of inherited blood disorders characterized by reduced or no hemoglobin. It affects people of Mediterranean descent.

  • Aplastic anemia (caused by damage to the bone marrow and the blood stem cells within the bone marrow)
  • Megaloblastic anemia (also called pernicious or vitamin B12 deficiency, caused by vitamin B12 deficiency in individuals unable to absorb vitamin B12 from their intestines)
  • Folate deficiency anemia (due to folate deficiency)
  •  Bone marrow and stem cell issues
  • Chronic conditions such as kidney disease, cancer, HIV/AIDS

III. Anemia caused by high rates of red blood cell destruction

  • Hemolytic anemia (associated with immune disorders, infections, some medications, poor reactions to blood transfusions)


Anemia is diagnosed through a physical exam by the doctor as well as through blood tests to identify a specific type of anemia that may be present. Blood tests may include:

  • Blood levels of iron, vitamin B12, folic acid, and other vitamins and minerals
  • Red blood cell (RBC) count (to determine the count number and size of the RBCs)
  •  Hematocrit (percentage of a volume of blood composed of RBCs)Lower normal limit of hemoglobin and hemocrit by sex
  • Hemoglobin concentration
  • Additional blood tests
  • Bone marrow aspiration and/or biopsy

Other laboratory tests — liver function tests, kidney function test, and bone marrow biopsy  — also may be performed.


Treatment of anemia varies widely, depending on the cause and severity of the condition. The type of anemia must first be correctly determined before the proper treatment can be started. Since the treatment for anemia is always based on the specific type of disease, it is imperative that a qualified doctor make an exact diagnosis.

Mild anemia with no or minimal symptoms may be due to low iron levels and can be treated with iron supplements. Vitamin B12 injections are required for patients with pernicious anemia. Patients with severe types of anemia may need to be hospitalized. A rapidly bleeding stomach ulcer is treated with both medications to heal the ulcer and a blood transfusion to replace the depleted red blood cells, thereby reducing the symptoms of anemia. A patient who has sustained an injury may require a blood transfusion to correct extensive blood loss. Replenishing the patient’s blood improves symptoms of anemia.

Chemotherapy for cancer may cause bone marrow damage, and bone marrow damage can lead to anemia. Patients who are undergoing chemotherapy for cancer or who have bone marrow disease often require medications such as epoetin alfa to stimulate the production of red blood cells in bone marrow production. An elevated number of red blood cells increases the amount of hemoglobin in the blood so that more oxygen can be transported to tissues throughout the body.

Treatments for anemia depends on the cause may include:

  • Vitamin and mineral supplements (such as iron, vitamin B12, folic acid)
  •  Dietary change
  • Vitamin B12 injections (given monthly for pernicious anemia)
  • Erythropoietin (to increase blood cell production in bone marrow, especially in patients with kidney disease)
  • Blood transfusion
  • Bone marrow transplant
  • Surgery (to remove the spleen in hemolytic anemia)
  • Antibiotics (if anemia is caused by an infection)
  • Blood transfusions
  • Corticosteroids or other medications that suppress the immune system

Possible Complications

Anemia may be associated with negative health outcomes such as:

  • Reduced function and quality of life
  • Increased risk of congestive heart failure
  • Increased risk of myocardial infarction
  • Increased risk of dementia
  • Increased risk of complications due to medications taken for anemia

In severe anemia, the hemoglobin level may fall too low and reduce the amount of oxygen delivered to all of the tissues. Low levels of oxygen (hypoxia) in vital organs such as the heart may result in cardiovascular complications. Arrhythmias — problems with the rate or rhythm of the heartbeat — associated with anemia such may trigger a heart attack.


The prognosis, or outlook, of anemia is often good, depending upon the type and specific cause of the disorder. The severity of anemia, patient’s age, patient’s health, and patient’s compliance with treatment will affect recovery. The outcome is usually better in younger people than in elderly people. Anemia due to chronic medical conditions such as kidney failure, heart disease or lung disease may be more severe and usually requires ongoing, long-term monitoring and treatment.


A healthy lifestyle, including an appropriate diet, limited alcohol use, and regular medical checkups for blood tests can help to prevent anemia or, for those already diagnosed with the condition, keep it under control. Patients with sickle cell anemia or other chronic conditions should be monitored by medical professionals on a regular basis.

Anemia is a potentially serious condition because it may be linked with another underlying disease. If you have any signs and symptoms of anemia – fatigue, low energy, weakness, lightheadedness, shortness of breath, unusual bleeding — consult a medical doctor immediately for a full evaluation, including proper testing.


Balducci L. Anemia, cancer, and aging. Cancer Control. 2003;10(6)

56 Facts About Blood — America’s Blood Centers. Retrieved on April 8, 2013

Blood Facts and Statistics | American Red Cross. Retrieved on April 8, 2013.

Kasai D. Emergent Management of Acute Anemia. Medscape. May 26, 2011.

Medline Plus Encyclopedia. Anemia. Retrieved on April 4, 2013.

Naibili ST. Anemia. Symptoms, signs causes, treatments. EMedicineHealth.
Retrieved on April 4, 2013.

NIH National Heart, Lung and Blood Institute. What is anemia? Retrieved on April 4, 2013.

NIH National Heart, Lung and Blood Institute. Sickle cell. Retrieved on April 4, 2013.

Pinson P. Bleeding and acute blood loss anemia. 2012. ACP Hospitalist. American College of Physicians. Retrieved on April 8, 2013.

WebMd. Understanding anemia: the basics. Retrieved on April 4, 2013.