Red Blood Cells
Understanding the Red Blood Cell: What They Are and Why They Matter
People living with sickle cell disease and their families need to understand the basic science of red blood cells, how they’re made, what hemoglobin does, and why these cells matter.
What Red Blood Cells Do
Red blood cells (also called erythrocytes) are the most abundant cells in our blood and are responsible for carrying oxygen from the lungs to the rest of the body. They contain a protein called hemoglobin that binds oxygen and gives blood its red color. They also remove carbon dioxide, a waste gas, from tissues and help bring it back to the lungs to be exhaled.
How Red Blood Cells Are Formed
Red blood cells begin as blood stem cells in the bone marrow.
These stem cells can develop into:
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Red blood cells (carry oxygen)
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White blood cells (fight infection)
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Platelets (help with clotting)
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As they mature, red blood cells lose their nucleus and most internal structures so they can carry as much hemoglobin as possible — making them efficient oxygen carriers.
Understanding Hemoglobin Types
Hemoglobin comes in several types:
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Hemoglobin F (fetal) – made before birth
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Hemoglobin A (adult) – the most common type after birth
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Hemoglobin S (sickle) – the abnormal type that causes sickle cell disease when inherited in two copies