Ask A Scientist

Why does blood turn red when oxygen gets to it?

Asked by: Colin Szymanski
School: Maine Endwell Middle School
Grade: 6
Teacher: Kevin Wagstaff
Hobbies/Interests: Hockey and Lacrosse
Career Interest: Pro-Hockey player or Orthodontist

Answer from Nikki Austin, MS, MA, RN

Research Assistant, Binghamton University

Research area:
Exercise and Physical Activity, Gerontological Nursing

PhD School:
Enrolled in the Decker School of Nursing PhD program.

Our blood has many different kinds of cells. They are very tiny so that we can't see them without the help of a microscope. The red blood cells carry oxygen, white blood cells fight infection, and platelets form clots to help stop bleeding. There are more red blood cells than other cells and men generally have more than women. Red blood cells are designed to carry a protein molecule called hemoglobin. The oxygen we breathe binds together with the hemoglobin to form oxyhemoglobin, which turns our blood red. If a person doesn't have enough red blood cells, or enough hemoglobin, we say that he is anemic and that his body may have difficulty maintaining a high oxygen level which could make that person very sick. Or, a person might have a lung disease such emphysema, or might be breathing air that doesn't have enough oxygen (perhaps in a house fire). When a person doesn't get enough oxygen in the blood, the skin color may even turn a bit blue. We call that blue color cyanosis and it may first be noticeable in places like the fingertips or inside of the mouth and lips. To prevent cyanosis in people who are sick or injured, health care professionals may give someone oxygen through a plastic tube that sits in the nose, or by a mask. We can measure oxygen levels by using a small device called a pulse oximeter. It can sense the blood flowing under your skin and can measure what we call oxygen saturation. Red blood cells live about 80 to 120 days and your body makes a continual supply. But, when people lose a lot of blood, maybe from surgery or an accident, they will need to have those red blood cells replaced faster than the body can make them. That is why you see advertisements for blood drives and you may know an adult who has donated blood. You might even ask a blood donor what it was like to give blood or you might ask the Red Cross to come to your class to tell you more about their lifesaving blood mobiles. Thanks for the great question!

Last Updated: 3/1/17