by Rosemarie Tremblay-LeMay MD FRCPC
May 26, 2022

What is anemia?

Anemia is a decreased amount of hemoglobin in the blood. This can be due to a decrease in the number of red blood cells (RBCs) in your blood or a decrease in the amount of hemoglobin in each RBC. Because the body uses oxygen to make energy, a person with anemia has less oxygen in their blood which can make them feel tired or short of breath.

Hemosiderin and red blood cells

The blood contains many different types of cells. These cells include immune cells and red blood cells (RBC). RBCs are responsible for carrying oxygen from your lungs to the rest of your body and carrying carbon dioxide back to the lungs. They hold on to oxygen and carbon dioxide using a specialized protein called hemoglobin.

Normal red blood cells

Red blood cells are made in a part of the bone called the bone marrow. As young RBCs mature in the bone marrow, they produce hemoglobin. Your body needs iron in order to make hemoglobin for RBCs. Once this process is complete, the RBCs are released into the bloodstream. Normal, healthy RBCs circulate in the bloodstream for about 120 days before they are removed, and their iron is recycled to make new RBCs.

Extra iron is stored in a specialized protein called ferritin. The amount of ferritin will change as the amount of iron in your body changes. For example, a person with low levels of iron in their body will have low levels of ferritin in their blood.

What causes anemia?

Anemia can be caused by anything that decreases the number of RBCs in your blood or the amount of hemoglobin found in each RBC. In some situations, a person may have more than one reason for developing anemia.

The causes of anemia are often divided into three groups:

  1. Conditions where not enough RBCs are produced.
  2. Conditions where RBCs cannot mature normally.
  3. Conditions where RBCs are removed from the bloodstream faster than normal (less than 120 days).

Related articles

Anemia of chronic disease

Hemolytic anemia

Iron deficiency anemia

Megaloblastic anemia

Other helpful references

Government of Quebec – Iron-rich foods

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