The red blood cell (RBC) count is a test that measures the number of oxygen-carrying blood cells in your blood. An abnormal RBC test result is often the first sign of an illness. The test requires a simple blood sample.

The red blood cell or erythrocyte is an unusual, unique, and highly differentiated cell without organelles or the ability to divide. The erythrocyte is central to body physiology as it is responsible for oxygen transport through the bloodstream.

Low levels of the protein in red blood cells that carry oxygen, called hemoglobin, is the main sign of anemia. Some people learn they have low hemoglobin when they donate blood. If you're told that you can't donate because of low hemoglobin, make a medical appointment.

Causes. By Mayo Clinic Staff. Low oxygen levels, misuse of certain drugs and blood cancers can cause a high red blood cell count. The body might make more red blood cells as a response to conditions that result in low oxygen levels. These might include: Congenital heart disease in adults. COPD. Heart failure.

The red blood cells are highly specialized, well adapted for their primary function of transporting oxygen from the lungs to all of the body tissues. Red cells are approximately 7.8 μm (1 μm = 0.000039 inch) in diameter and have the form of biconcave disks, a shape that provides a large surface-to-volume ratio.

Red blood cells, also called erythrocytes, are the most abundant cell type in the blood. Other major blood components include plasma, white blood cells, and platelets. The primary function of red blood cells is to transport oxygen to body cells and deliver carbon dioxide to the lungs.

The red blood cells or erythrocytes are red-colored cells having a biconcave shape. They are flattened discs lacking nuclei and cytoplasmic organelles, containing the red protein hemoglobin for gas transport, primarily oxygen and some carbon dioxide.

Erythrocytes, red blood cells (RBC), are the functional components of blood responsible for transporting gases and nutrients throughout the human body. Their unique shape and composition allow for these specialized cells to carry out their essential functions.