Function of Red Blood Cells


What are red blood cells?

Red blood cells, also known as erythrocytes, deliver oxygen to the tissues in your body. Oxygen turns into energy and your tissues release carbon dioxide. Your red blood cells also transport carbon dioxide to your lungs for you to exhale.


What do red blood cells do?

Red blood cells are responsible for transporting oxygen from your lungs to your body’s tissues. Your tissues produce energy with the oxygen and release a waste, identified as carbon dioxide. Your red blood cells take the carbon dioxide waste to your lungs for you to exhale.

Do red blood cells carry oxygen?

Yes, a red blood cell takes oxygen from the lungs to the tissues in your body. Your cells use oxygen to produce energy.


Where are red blood cells made?

Red blood cells develop in your body’s soft bone tissue (bone marrow) and release into your bloodstream after they fully mature, which takes about seven days.

What do red blood cells look like?

Red blood cells get their bright red color from a protein that allows them to carry oxygen from your lungs and deliver it to other tissues in your body (hemoglobin).

Red blood cells are microscopic and have the shape of a flat disk or doughnut, which is round with an indentation in the center, but it isn’t hollow. Red blood cells don’t have a nucleus like white blood cells, allowing them to change shape and move throughout your body easier.

What are red blood cells made of?

Red blood cells grow in your bone marrow. Bone marrow creates almost all of the cells in your body. Red blood cells contain a protein called hemoglobin, which is responsible for carrying oxygen.

Conditions and Disorders

What are the common conditions that affect red blood cells?

Red blood cell conditions have either a low or high red blood cell count.

Medical conditions that affect a low red blood cell count include:

  • Anemia: Your blood carries less oxygen than normal and causes your body to feel cold, tired and weak.
  • Blood loss: Your body loses more blood cells than it can produce.
  • Bone marrow disorder: You experience damage to your bone marrow, where red blood cells form (leukemia, lymphoma).
  • Cancer: Certain cancers and chemotherapy treatment for cancer can affect the number of red blood cells your body produces.

Medical conditions that affect a high red blood cell count include:

What are common symptoms of red blood cell conditions?

  • Fatigue.
  • Muscle weakness.
  • Lack of energy.
  • Headache or dizziness.
  • Blurry vision.
  • Cold hands and feet.

What causes a low red blood cell count?

Causes that contribute to low red blood cell count include:

  • Vitamin deficiency (iron, B9 and B12).
  • Malnutrition.
  • Preexisting medical conditions or cancer treatment (chemotherapy).

What causes a high red blood cell count?

Causes that contribute to a high red blood cell count include:

  • Smoking cigarettes.
  • Living at a high elevation.
  • Taking performance-enhancing drugs (anabolic steroids).
  • Dehydration.
  • Medical condition including heart or lung disease.

What are common tests to check the health of my red blood cells?

A complete blood count (CBC) test examines how many blood cells (red and white) are in your blood. A medical professional will sample your blood to count how many red blood cells are present.

What is a normal red blood cell count?

Normal red blood cell counts differ based on the individual:

  • Men: 4.7 to 6.1 million red blood cells per microliter of blood.
  • Women: 4.2 to 5.4 million red blood cells per microliter of blood.
  • Children: 4.0 to 5.5 million red blood cells per microliter of blood.

If your count is outside of these ranges, it is either too high or too low and your healthcare provider will offer additional tests or treatments.

What are common treatments for red blood cell disorders?

Treatment for red blood cell disorders varies based on the diagnosis and severity of the condition. Treatment ranges from:

  • Taking vitamins.
  • Eating a well-balanced diet.
  • Treating existing medical conditions.
  • Getting a blood transfusion.


How do I take care of my red blood cells?

You can maintain healthy red blood cells by eating a nutritious diet that is full of vitamins and minerals like iron, B9 (folic acid) and B12, which includes:

  • Red meat (beef) and meat from the organs, like liver.
  • Fish.
  • Leafy vegetables, like kale and spinach.
  • Lentils, beans and peas.
  • Nuts and dried berries.

Frequently Asked Questions

What is hemoglobin within red blood cells?

Hemoglobin is the protein that carries oxygen and exists within each red blood cell. If your red blood cell was a vehicle, hemoglobin is in the driver’s seat, picking up oxygen at the lungs and transporting it to the tissues throughout your body.

What are interesting facts about red blood cells?

  • Red blood cells have a limited lifespan because they don't have a center membrane (nucleus). When a red blood cell travels through your blood vessels, it uses up its energy supply and only survives an average of 120 days.
  • Your blood appears red because red blood cells make up 40% of your blood.

A note from Cleveland Clinic

Red blood cells are constantly moving throughout your body to bring oxygen to your tissues, and release carbon dioxide as you exhale. Keep your red blood cells healthy by eating a nutritious diet full of vitamins and minerals, and avoid smoking to reduce your risk of red blood cell disorders.

Last reviewed by a Cleveland Clinic medical professional on 08/11/2021.


  • American Association for Clinical Chemistry/Lab Tests Online. Red Blood Cell Count (RBC). ( Accessed 9/3/2021.
  • American Society of Hematology. Blood Basics. ( Accessed 9/3/2021.
  • Merck Manual. Components of Blood. ( Accessed 9/3/2021.
  • National Health Service. Red blood cell count. ( Accessed 9/3/2021.
  • National Heart, Lung, and Blood Institute. Anemia. ( Accessed 9/3/2021.
  • StatPearls. Histology, Red Blood Cell. ( Accessed 9/3/2021.

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