RBCs start their journey as reticulocytes in the bone marrow, initially having some organelles and a nucleus which they lose as they mature into erythrocytes.

They serve your body for about 120 days before being decommissioned by macrophages in the liver and spleen.

Erythropoietin, a hormone predominantly produced in the kidneys, is the master regulator of RBC production, particularly when oxygen levels are low, like in lung diseases or anemia.

It stimulates stem cells in the bone marrow to produce more RBCs and accelerates their development.

Iron, vitamin B-12, and folate are key nutrients in this process.

RBCs dominate your bloodstream, both in number and function, giving blood its characteristic red color.

Men typically have about 5.2 million RBCs per cubic millimeter, while women have around 4.6 million.

They make up 40 to 45 percent of your blood, a ratio known as the hematocrit.

For every white blood cell in your body, there are about 600 RBCs and 40 platelets.

Their distinct biconcave disc shape aids in their flexibility, allowing them to navigate through tiny capillaries effortlessly.

They also lack a nucleus, enabling more room for hemoglobin, the protein responsible for oxygen transport.

The primary role of RBCs is oxygen delivery.

Hemoglobin in RBCs, with its iron atoms, can bind up to four oxygen molecules, efficiently transporting oxygen from the lungs to body tissues.

In the lungs, hemoglobin picks up oxygen and releases it in tissues where it's needed. This process significantly increases the blood's oxygen-carrying capacity.

An RBC is composed of about one-third hemoglobin.

Normal hemoglobin levels are around 15.5 grams per deciliter in men and 14 grams in women.

Besides transporting oxygen, RBCs also help remove carbon dioxide, carrying about 70 percent of it as bicarbonate ions, with the remainder dissolved in plasma or bound to hemoglobin.

In summary, RBCs are the VIPs of your circulatory system, delivering oxygen to where it's needed and ensuring carbon dioxide is efficiently removed from your body.