Mature red blood cells are just basically bags of hemoglobin, so the cells themselves don’t have much “function” even though they are extremely important. As you probably know, hemoglobin carries oxygen to our cells and carries some of the carbon dioxide away from cells. A person who is having problems with their red cells can’t get enough oxygen and will be tired, feel breathless, and may have less color. For example, a person with light skin will look pale. In a person with dark skin, you can still see less color, especially in places like the gums.

If a person does not get enough iron, they can’t make enough hemoglobin (which contains iron). This is a the most common form of anemia. “Anemia” means not having enough of a blood cell.

Hemoglobin can malfunction. In sickle-cell disease, hemoglobin does something odd. When it has given up oxygen, it changes shape, changing the shape of red blood cells. A sickle is a curved blade that used to be used to harvest crops. The oddly-shaped blood cells of people with this disease reminded someone of sickles. Normal red blood cells are shaped like a Lifesaver that doesn’t quite have a hole in the middle. These can squeeze through our smallest blood vessels (capillaries) pretty easily. With sickle-cell disease, the cells can get stuck in the small blood vessels. All of the cells “downstream” from the blockage are then starved for oxygen and nutrients and die. Sickle-cell disease is genetic.

There are other diseases that can cause a person to have problems with their red blood cells. There are a few different problems lumped together to mean that red blood cells are being destroyed. These problems are types of “Hemolytic anemia.” “Hemo” means blood. “Lysis” means breakdown. The body should destroy red blood cells that are 3 or 4 months old and worn out. But sometimes the body attacks healthy cells. Some infections attack red blood cells. When people run or march long distances, or play drums for a long time, or do other things that cause a lot of pounding, blood cells can get broken up. These are all causes of hemolytic anemia.

Some people do not make enough red blood cells because of a problem in their bone marrow.

Other diseases include having sphere-shaped red blood cells, too many red blood cells, or too much iron in the blood.