What is RBC in blood test results?

What is RBC? | Why is RBC tested? | Normal RBC range | Factors that affect RBC | Low RBC | High RBC

The body is made up of cells, tissues, and organs that work together to keep the body functioning. These cells include red blood cells, white blood cells, and platelets, which have unique and important features and are involved in various processes. A problem with these cells can lead to serious conditions, which need routine lab tests to monitor. 

A red blood cell (RBC) test is one of the most common blood tests for getting a snapshot of overall health. Getting an RBC test is standard as part of a complete blood cell (CBC) panel, and a healthcare provider will typically order a CBC panel at routine health visits to check for abnormalities. That’s because knowing RBC levels can tell a lot about different medical conditions and the effects of some medications. For example, low RBC levels may indicate a problem like anemia. 

Continue reading to learn more about the RBC blood test, normal range, and what low or high RBC levels could mean. 

What is RBC?

RBCs, also known as erythrocytes, make up almost half of the volume of blood. These cells are produced in the bone marrow and are shaped as flexible discs (similar to the appearance of a donut). The main component of RBCs is a protein called hemoglobin, which delivers oxygen to all body parts from the lungs. Red blood cells are part of three main types of cells that make up the blood. 

The three main types of blood cells are:

• Red blood cells (RBCs or erythrocytes)
• White blood cells (WBCs, including neutrophils, eosinophils, basophils, monocytes, macrophages, and lymphocytes) 
• Platelets

The main types of blood cells differ in their primary functions. RBCs carry oxygen throughout the body, while WBCs defend the body against viruses, bacteria, and other pathogens that can cause infections. Platelets are cells that help form clots to prevent or stop bleeding. 

The role of hemoglobin

Hemoglobin is a vital iron-rich protein that all red blood cells contain and is what gives red blood cells their color. Without hemoglobin, red blood cells can’t bind to oxygen and deliver it from the lungs to the tissues and organs of the body. Hemoglobin also carries carbon dioxide from the tissues back to the lungs to be expelled. 

As all RBCs contain hemoglobin, low RBC levels lead to low hemoglobin levels. However, certain conditions can affect the hemoglobin in RBCs, possibly leading to low hemoglobin levels even with a normal RBC count. 

Why RBC levels are tested

A red blood cell count is always included as part of a complete blood count panel. RBC levels can provide valuable information about certain symptoms and conditions, including anemia, certain blood cancers, and nutrition or hydration status. If you experience certain symptoms, a doctor or healthcare provider may order an RBC test for more information. These symptoms include:

• Tiredness
• Weakness
• Fever
• Diarrhea
• Bruising

As part of an CBC test, the number of red blood cells is measured along with levels of white blood cells, hemoglobin, platelets, and hematocrit. Hematocrit levels measure the volume of the body’s red blood cells or the proportion of red blood cells that make up the blood. Other diagnostic tests, such as iron tests and blood smears, may be conducted along with an RBC test. 

Drawing a blood sample

An RBC test, like other blood tests, requires a blood sample. A healthcare professional trained in phlebotomy will draw blood from a vein in an arm using a needle and collect the sample in a test tube. The sample will then be analyzed in a laboratory. For some people, a blood draw may cause temporary discomfort. Other risks of drawing blood include:

• Fainting
• Blood clots under the skin (hematoma)
• Severe bleeding
• Infection

The risk of a serious problem is minimal when a trained professional is performing the blood draw. There is little risk of serious effects, and any slight bruising or discomfort should ease within a few days. 

Normal RBC levels

Normal RBC levels can vary among different people. However, most normal RBC levels will fall in a specific reference range. This range may vary slightly depending on the healthcare provider or laboratory. The normal reference range can be found in the following table.

After measuring the number of red blood cells, a healthcare provider will be better able to tell what is causing certain health problems you’re experiencing. You may need follow-up RBC tests or additional tests to monitor your health. Discuss the test results and lab values with a healthcare provider. The results of these tests could be a sign of one of many health problems. 

Factors that affect RBC

There can be several different causes of an abnormal erythrocyte count. These risk factors involve the following:

• Medical conditions
• Infectious diseases
• Medication use
• Genetic mutation
• Pregnancy 
• Age 
• Nutrition and diet
• Blood volume changes
• Smoking
• Dehydration
• Bone marrow problems
• Altitude

Various health issues can lead to abnormally high or low RBC levels. A healthcare provider will recommend an appropriate treatment depending on the cause of the abnormal RBC levels. These treatment options may include dietary and lifestyle changes, as well as prescription or over-the-counter (OTC) medicines. 

Low RBC levels

A low RBC count usually indicates low hemoglobin levels, which means insufficient oxygen will be carried throughout the body. The medical term for low red blood cell levels is anemia.

Causes

Different health conditions can lead to a low erythrocyte count. These conditions include sickle cell anemia, bone marrow problems, chronic kidney disease, and internal bleeding or blood loss. Leukemia, a type of blood cancer, or a viral or bacterial infection can also disrupt the number of red blood cells. 

Some medications and treatments, such as cancer treatment, may cause a low RBC count. Cancer treatment can affect the function of the bone marrow, which plays a major role in producing enough healthy red blood cells. 

A folate deficiency can sometimes lead to a low RBC count. Being deficient in other vitamins, such as B6 and B12, may also contribute to anemia. 

Symptoms

The signs and symptoms of a low RBC count include:

• Weakness
• Fatigue
• Shortness of breath
• Fast heart rate
• Dizziness
• Pain in the chest
• Swelling in the hands or feet

The symptoms of anemia can range from mild to severe. Consult a healthcare provider if you experience any abnormal symptoms, as you may need prompt medical treatment. Left untreated, a low red blood cell count could lead to complications. 

Treatments

The treatment for a low RBC count will depend on the underlying cause. Eating a nutrient-rich diet or supplements may help correct a low RBC count for people deficient in iron or certain vitamins. If a specific medical condition, such as chronic kidney disease, causes a low RBC count, a healthcare provider will aim to treat the medical condition in question. Lifestyle changes, such as regularly exercising, may help stimulate an increase in red blood cells. 

High RBC levels

A high red blood cell count can cause the blood to be thicker than usual, increasing the risk of blood clots, heart attacks, and strokes. The medical term for high RBC levels is erythrocytosis. 

Causes

High RBC levels can have several different causes. Medical conditions, such as heart failure, sleep apnea, and lung disease, can be a possible cause. Dehydration and kidney problems may contribute to a high RBC count. Lifestyle factors like living at a higher altitude or smoking tobacco may also increase red blood cells. 

Polycythemia vera is a rare blood disorder that causes the blood marrow to produce too many red blood cells. It is caused by a genetic mutation that can develop during a person’s lifetime. 

Symptoms

Some symptoms of a high RBC count are similar to those of a low RBC count. The signs and symptoms of a high RBC count include:

• Dizziness
• Fatigue
• Headache
• Shortness of breath
• Bruising or bleeding more than usual
• Bleeding gums
• Nosebleeds
• Blurred vision
• High blood pressure

In some cases, a high RBC count may not cause any symptoms. In other cases, signs or symptoms may not appear until the underlying condition has progressed. A healthcare provider will evaluate your overall medical history and symptoms to determine the best treatment option. 

Treatments

A healthcare provider will aim to treat the underlying cause of a high RBC count. Treatment may include certain procedures or prescription drugs. For people with polycythemia vera, a healthcare provider may recommend a prescription medication like hydroxyurea or chemotherapy to reduce the production of red blood cells. Regular blood draws may also be needed to manage red blood cells. 

Bottom line

A doctor or healthcare provider can manage most cases of an abnormal number of red blood cells. However, routine lab tests can help catch a problem before it becomes serious. The symptoms of a high or low RBC count can range from mild to life-threatening. In life-threatening cases, experiencing severe symptoms may be a medical emergency and require immediate medical attention. However, treatment options, including lifestyle changes, vitamins, and prescription medications, are available to help control red blood cell levels.