Red Blood Cells: What Do They Do?

11/22/2021 | 5 min. read

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Each of the four components that make up the blood has its own vital job to do. When they work together, they keep us healthy in a variety of crucial ways. One of those components, the red blood cell, may be small in size, but they are huge in importance.

To help you better understand what your red blood cells do and what makes them such an essential part of your health and wellbeing, the experts at Healthy Directions present this primer.

What Is a Red Blood Cell?

Red blood cells, also known as erythrocytes, are the blood component that gives it its red color.

When we look at the components of the blood — white blood cells (WBCs), red blood cells (RBCs), plasma, and platelets — the red blood cells make up about 40-45% of the total volume. That makes it the second most prevalent component after plasma (which makes up about 55% of the blood’s volume).

Our red blood cells are produced inside the bone marrow, where they are also stored for up to four months (around 120 days). When the body needs to manufacture more RBCs, the kidneys produce a hormone known as erythropoietin which triggers their production.

At any given time, adults have about 25 trillion RBCs in circulation.

What Do Red Blood Cells Look Like?

Although we can’t see red blood cells with the naked eye, they have a very specific shape when viewed under a microscope. This biconcave shape is crucial to their function and helps them perform their most critical task — carrying oxygen throughout the body.

While they are flat and round, they also have a large indentation in the center on both sides. That indentation is thinner than the remainder of the cell, allowing the cell to fit into the smaller capillaries and facilitate the exchange of oxygen and carbon dioxide.

Even though that may sound like a small thing, it can be a huge problem when there are issues with the size and shape of the red blood cells. Mainly, these problems come from the RBCs becoming less capable (or even entirely unable) to carry oxygen throughout the body successfully.

Another unique fact about the red blood cell is that it does not contain a nucleus, ribosomes, or mitochondria. That leaves more open space on the surface of the RBC to fit millions of hemoglobin proteins.

What Do Red Blood Cells Do?

The primary function of the red blood cells is to carry oxygen from the lungs to the rest of the body’s tissues. Without them, we wouldn’t be able to provide the body with proper oxygenation, which is necessary for survival.

However, the role of the red blood cell doesn’t stop there. In addition to providing oxygen to the body, RBCs also transport waste products (including, most importantly, carbon dioxide) back to the lungs where it is exhaled.

Red blood cells would be nothing without hemoglobin, though. While red blood cells are the transport device, hemoglobin is the protein that allows them to actually hold onto and carry oxygen. They work hand in hand to perform one of the blood’s most essential roles in the body.

In addition, red blood cells also help to determine blood type. Part of how blood type (which is either A, B, or O) is decided is by looking for either the presence or absence of antigens on the surface of the red blood cell.

Without it, the body may start to attack its own RBCs as though they were foreign bodies invading the blood.

What Issues Can Happen With Your Red Blood Cells?

Unfortunately, the health and functionality of the red blood cells doesn’t always happen at an optimal level. Specific issues can occur that impact how well the RBCs can do their job. Often, the result is that there aren’t enough red blood cells in the body to meet the demand.

One of the most common results of red blood cell-related issues is anemia. With a low red blood cell count, the body cannot supply oxygen to the body. This is why people who have anemia (sometimes referred to as iron deficiency) often complain of fatigue, dizziness, and weakness. Anemia can happen due to multiple different issues, including blood loss due to trauma, blood disorders like sickle cell disease, vitamin b-12 deficiency, leukemia, or even post-surgery.

How You Can Support Your Red Blood Cells

The number one thing you can do to help support your red blood cells is to eat a healthy diet. More specifically, you’ll want to focus on foods that are rich in iron.

Iron-rich foods include green leafy vegetables (like kale and spinach), meat (or tofu if you follow a plant-based lifestyle), lentils, red meat like beef, and beans. Iron is necessary to maintain the health of the red blood cells and can also help protect your cardiovascular health.

B-complex vitamins, especially B-2, B-3, B-12, and folic acid or folate, are also crucial for RBC production and overall health. Bananas, eggs, orange juice, and certain fortified foods like cereals can help you meet your recommended daily requirements for each of those micronutrients that boost your number of RBCs.

To help check the health of your red blood cells, it’s a good idea to have regular blood work and labs performed on your vein.

A complete blood count (CBC) measures not only your red blood cell count but also checks your hemoglobin level, white blood cell count, hematocrit (how much plasma you have in your blood), and platelet count.

To Summarize

Although each component of the blood is essential, the red blood cells can make or break the functionality of the entire rest of the body.

Due to their crucial role in transporting oxygen throughout the body through blood flow in your arteries, it is vital that you do everything you can to help maintain their health.

Eating iron-rich foods, getting regular blood work, and having any new symptoms checked by a medical professional can keep your body working at its most optimal level.

Healthy Directions is here for you every step of the way.


Shape and Biomechanical Characteristics of Human Red Blood Cells in Health and Disease | NIH (

What Do Blood Cells Do? | American Red Cross (

Iron-Rich Food | List of Meats And Vegetables | Red Cross Blood

Healthy Directions Staff Editor