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What Causes Anemia in the Human Body?

By Stephen Christensen ; Updated September 26, 2017

Every cell in the human body requires oxygen to function. Hemoglobin, an iron-containing protein found in your red blood cells, is uniquely designed to capture oxygen in your lungs and transport it to the rest of your body. Anemia develops when you do not have a sufficient number of functional red blood cells in your circulation to meet your body tissues' demands for oxygen. Any process that interferes with red blood cell production, increases red blood cell destruction or leads to blood loss can cause anemia.

Iron Deficiency

According to the World Health Organization, iron deficiency is the most common nutritional disorder worldwide. Iron-deficiency anemia is believed to be the most common form of anemia globally. Iron is required for the production of hemoglobin. If your iron stores are depleted, you cannot manufacture enough red blood cells to meet your needs. Inadequate dietary iron intake and chronic gastrointestinal blood loss due to ulcers or parasitic infections are common causes of iron deficiency.

Acute Blood Loss

Anemia often follows the sudden loss of a large volume of blood due to trauma or disease. Since your body stores some iron, anemia caused by acute blood loss may only persist for a few weeks until your bone marrow has produced enough new red blood cells to replace those lost. However, if your iron stores are depleted for any reason -- poor nutrition, for example -- you may need to take iron supplements for several months until your red blood cell level is restored. Massive blood loss may warrant a blood transfusion to prevent severe anemia.

Red Blood Cell Destruction

A red blood cell circulates in your bloodstream for about 120 days before it is broken down and its iron is recycled to make new blood cells. A variety of conditions can trigger the early destruction of red blood cells, including autoimmune diseases, such as lupus; infections, such as malaria; and genetic disorders, such as sickle cell disease, glucose-6-phosphate dehydrogenase deficiency and thalassemia. Due to the premature removal of red blood cells from your circulation, any of these conditions can cause anemia.

Reduced Red Blood Cell Production

Red blood cells are manufactured in your bone marrow before being released into your circulation. This manufacturing process, called hematopoiesis, can be disrupted by toxins, such as chemotherapy drugs; heavy metals, such as lead; nutritional disorders, such as vitamin B12 or folate deficiencies; cancers, such as lymphoma or multiple myeloma; chronic diseases, such as kidney failure; or "marrow failure" syndromes, such as aplastic anemia or myelodysplasia. Inefficient hematopoiesis leads to a gradual decline in the number of circulating blood cells and eventually results in anemia.

Signs and Symptoms

Since anemia is characterized by a reduction in your blood’s ability to deliver oxygen to your tissues and organs, the signs and symptoms of anemia stem from poor oxygenation. Fatigue, dizziness, reduced exercise tolerance, shortness of breath, difficulty concentrating and paleness are among the most common manifestations of anemia. In older people, anemia can lead to disorientation, confusion, chest pain, loss of consciousness or even congestive heart failure or heart attack.


Treatment for anemia is based on its underlying cause. Iron deficiency usually responds to iron supplementation. Anemia due to kidney failure or other chronic diseases may respond to hormones that boost hematopoiesis. Bone marrow failure may require frequent transfusions to maintain your red blood cell level. If toxins, infections or nutritional deficiencies are responsible for your anemia, these problems must be addressed before the anemia will resolve. A bone marrow transplant may be warranted in some conditions, such as sickle cell disease, thalassemia or aplastic anemia. Your doctor will determine the best treatment approach for you.

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