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Hemoglobin refers to a protein, found in red blood cells, that is responsible for carrying oxygen from the lungs to all other tissues of the body. Red blood cells circulate through the lungs and the hemoglobin in these cells pick up (bind with) oxygen. These cells carry the oxygen, in a form called oxyhemoglobin, out to the tissues and cells of the body. Once at the proper destination, the oxyhemoglobin releases the oxygen and becomes hemoglobin again. The red blood cells, carrying hemoglobin (without oxygen), circulate back to the lungs to pick up more oxygen, and the process begins again.

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it's your red blood cells. They carry oxygen around the body to the organs, brain, skin, etc.

It's why I like to eat chicken, beef, or lambs liver!  Those iron-rich meats are the best supply of iron to make plenty of hemoglobin!