I. Introduction

An abnormal RBC count has many potential causes, but iron-deficiency anemia, normocytic anemia, and microcytic anemia are among the most common. According to the American Academy of Family Physicians, iron-deficiency anemia affects 2% of adult men, 9% to 12% of non-Hispanic white women, and nearly 20% of Mexican-American and black women. The incidence of normocytic anemia depends on the underlying cause. Anemia of chronic disease, which is the most common type of normocytic anemia, affects approximately 6% of hospitalized adults. The incidence of microcytic anemia also depends on its underlying cause.

This guide offers information on red blood cell count testing, including when it’s ordered, why it’s ordered, and how it’s performed. It also contains information on the causes, symptoms, and treatment options of three common causes of abnormal RBC counts: iron-deficiency anemia, normocytic anemia, and microcytic anemia.

II. Overview of the Red Blood Cell Count

Why should I get tested?

The purpose of the RBC count is to determine how many red blood cells are in a sample of blood. An abnormal RBC count can indicate the presence of an underlying disease, making this test an important diagnostic tool. The RBC count can help in the diagnosis and management of kidney problems, certain types of cancer, blood disorders, and disorders of the bone marrow. It may also be ordered as part of a routine physical to establish a baseline that can be compared against in the future.

When should I get tested?

According to MedlinePlus, a red blood cell count is almost always performed as part of a complete blood count, which is a blood test that measures RBCs, white blood cells (WBCs), platelets, and hemoglobin, the substance in RBCs that carries oxygen. The RBC count should also be performed under the following conditions:

  • After starting chemotherapy, which can reduce the number of RBCs, WBCs, and platelets in the blood
  • When taking medications that can increase or decrease the RBC count (e.g., methyldopa, quinidine, gentamicin)
  • When displaying symptoms of a low RBC count, including weakness, shortness of breath, fatigue, and/or dizziness
  • When undergoing monitoring for a chronic illness that can cause an abnormal RBC count (e.g., kidney cancer, bone marrow failure)

What is required for the test?

An RBC count test requires a blood sample drawn from a vein.

How do I prepare for the test?

No special preparation is needed for an RBC count test.

III. The Basics of Iron-Deficiency Anemia, Normocytic Anemia, and Microcytic Anemia

Iron-Deficiency Anemia

Iron-deficiency anemia occurs when an individual does not have enough iron, a mineral involved in the production of red blood cells. The lack of iron results in a lower-than-normal RBC count. Iron deficiency has several causes, including poor iron absorption, inadequate iron intake, increased demand for iron due to pregnancy or breastfeeding, and losing iron faster than the body can replace it. Poor iron absorption often occurs in individuals who have celiac disease or Crohn’s disease, but taking antacids and having gastric bypass surgery can also interfere with iron absorption. In some people, bleeding leads to iron loss. Bleeding may be due to heavy menstrual periods, gastrointestinal bleeding caused by long-term aspirin use or cancers of the digestive system, peptic ulcer disease, or enlarged veins in the esophagus.

Mild iron-deficiency anemia doesn’t always cause symptoms. As the deficiency becomes worse, the individual may experience heart palpitations, headaches, dizziness, weakness, difficulty concentrating and thinking clearly, and fatigue. Severe iron deficiencies can cause symptoms such as pale skin, brittle nails, mouth ulcers, hair loss, shortness of breath, and restless legs during sleep.

Normocytic Anemia

Normocytic anemia is characterized by a low number of normal-sized red blood cells. In some people, normocytic anemia is congenital, which means it’s present at birth. For example, sickle-cell anemia is a congenital form of normocytic anemia. This condition may also be acquired, which means it’s caused by illness or infection. Cancer, inflammation of the thyroid gland (thyroiditis), kidney disease, and rheumatoid arthritis are examples of illnesses that can cause normocytic anemia to develop.

Like iron-deficiency anemia, normocytic anemia may not cause any symptoms right away. As it gets worse, the individual is likely to develop pale skin, experience dizziness or weakness, or feel tired even with little activity.

Microcytic Anemia

Microcytic anemia differs from normocytic anemia because the red blood cells are smaller than normal. In contrast, people with normocytic anemia have normal-sized RBCs. In addition to the reduced size of the red blood cells, microcytic anemia can also cause the RBCs to be paler than normal (hypochromic). The symptoms of microcytic anemia are the same as those of iron-deficiency anemia and normocytic anemia: pale skin, shortness of breath, dizziness, fatigue, loss of stamina, and weakness.

Hypochromic microcytic anemia occurs when there is not enough hemoglobin in the red blood cells. Thalassemia and sideroblastic anemia are two types of hypochromic microcytic anemia. Thalassemia is an inherited blood disorder in which the body doesn’t produce enough hemoglobin or produces abnormal hemoglobin, while sideroblastic anemia is a blood disorder that renders the bone marrow unable to produce normal RBCs. Normochromic microcytic anemia is a type of microcytic anemia in which the RBCs have enough hemoglobin. This type of microcytic anemia may be caused by kidney disease, cancer, serious infections, and inflammatory diseases like rheumatoid arthritis and Type 2 diabetes.

IV. How a Red Blood Cell Count Works

The RBC count determines how many red blood cells are present in a blood sample, with the value expressed as millions of RBCs per microliter of blood. Several laboratory techniques are used to perform a red blood cell count. Although RBCs can be counted manually with a hemocytometer, this method is time-consuming. The hemocytometer is typically reserved for counting RBCs in cerebrospinal fluid and other bodily fluids that have fewer than 1,000 RBCs per microliter.

Flow cytometry counters and impedance counters are also used to count the number of RBCs in a sample. With flow cytometry, a laser light detector detects scattered light from the particles in the sample, making it possible to determine the number of RBCs present. Impedance counters count the cells in a sample by measuring their electrical resistance. The settings can be adjusted to exclude platelets, making the RBC count more accurate.

To perform a red blood cell count, an adequate blood sample must be obtained from one of the veins, the blood vessels that carry blood back to the heart. The collection procedure involves identifying a vein, choosing the right needle, cleansing the skin thoroughly, and inserting the needle into the vein so that blood drains into a collection tube. Blood draws have relatively few risks, although they can cause some discomfort and bruising. Some people also experience dizziness or fainting while having their blood drawn.

V. Treatment for Iron-Deficiency Anemia, Normocytic Anemia, and Microcytic Anemia

Iron-Deficiency Anemia

The treatment for iron-deficiency anemia focuses on replenishing lost iron stores. Treatment methods vary based on the cause of the anemia, as well as how severe it is. Some people with iron-deficiency anemia take oral iron supplements, which can replenish an individual’s iron stores in as little as three months. Lifestyle changes, such as adding more iron-rich foods to the diet, can also replenish iron stores and resolve iron-deficiency anemia. Spinach, pumpkin seeds, and tofu are among the iron-rich foods used in the management of this condition.

For severe iron-deficiency anemia, it may be necessary for an individual to receive intravenous iron or undergo a blood transfusion. Intravenous iron is delivered via one of the veins, replacing lost iron quickly. Blood transfusions increase the amount of iron in the blood by increasing the number of red blood cells available. In individuals who develop iron-deficiency anemia as a result of gastrointestinal bleeding, surgery can be used to stop bleeding in the GI tract.

Normocytic Anemia

In individuals with normocytic anemia, the treatment plan usually focuses on treating the underlying cause of the condition. For example, someone who has normocytic anemia due to rheumatoid arthritis (RA) might try an RA treatment to reduce inflammation and return the RBC count to normal. If normocytic anemia is the result of medication use, a medical professional might recommend that the individual stop taking the medication. In severe cases of normocytic anemia, erythropoietin can be used to stimulate the bone marrow to produce more RBCs. It’s important for individuals with normocytic anemia to work with their doctors to find a treatment program that works. Normocytic anemia has several causes, so a treatment that’s effective in one person may not be as helpful for another person.

Microcytic Anemia

The treatment for microcytic anemia also depends on the underlying cause. Treatments for thalassemia include folic acid supplements, iron chelation therapy, and blood transfusions. The human body uses folic acid to produce healthy red blood cells; supplements can increase the amount of folic acid available, resulting in the production of healthier RBCs. Iron chelation therapy removes excess iron from the body. Although iron supplements are often used to treat anemia, too much iron is dangerous. If an individual receives regular blood transfusions, too much iron can build up in the blood, resulting in the need for chelation. Blood transfusions help individuals with thalassemia by increasing the number of red blood cells that have normal hemoglobin, which can relieve symptoms such as fatigue and shortness of breath.

In individuals with sideroblastic anemia, vitamin B6 can be used to relieve symptoms. Blood transfusions are also used to increase the number of healthy RBCs available. If the sideroblastic anemia is due to the use of a certain medication or exposure to a toxic substance, stopping the medication or removing the toxin from the individual’s environment may allow the anemia to resolve.


What is a normal red blood cell count?

A normal result depends on whether the individual is a man or a woman. In men, a normal RBC count ranges from 4.7 million to 6.1 million RBCs per microliter of blood; in women, a normal RBC count ranges from 4.2 million to 5.2 million RBCs per microliter of blood, according to MedlinePlus. Normal ranges can vary slightly by laboratory, so it’s important to discuss the results with a medical professional to determine what is considered normal.

Is the RBC count the only blood test needed in the diagnosis and management of anemia?

No. An individual with anemia may also need to have the serum iron, transferrin, and ferritin tests. These tests can help determine the type of anemia present, as well as the cause of the anemia. The serum iron test measures how much iron is in the blood, and it’s useful for identifying anemia caused by chronic disease. This test can also be used to monitor individuals receiving treatment for iron-deficiency anemia, as it helps determine if a person’s iron level is too high or too low. The transferrin test determines the amount of transferrin, a protein, in an individual’s blood. Transferrin carries iron from the digestive tract, where it is absorbed, to other parts of the body. Ferritin is also a protein, and it is responsible for storing iron in the body’s cells. The ferritin test determines if an individual has the right amount of ferritin available.

Is a high or low RBC count always a problem?

Not always. The results of a red blood cell count must be considered along with other test results and an individual’s medical history to determine if concern is warranted. RBC counts do not remain constant; therefore, it’s possible for someone to have an abnormal result on Monday and a normal result on Friday. These variations may be perfectly normal. Furthermore, reference ranges are developed based on a reference population. Approximately 95% of population members are expected to have RBC values within the reference range; that means about 5% of population members may have RBC values outside the reference range, even if they are perfectly healthy.

Can the environment affect an individual's RBC level?

Yes. Some environmental factors can affect a person’s RBC count. For example, an individual’s RBC count typically increases at high altitudes. The RBC count may be elevated for several weeks after visiting a high-altitude location.

What drugs affect the RBC count?

Anabolic steroids are among the substances known to affect an individual’s RBC count. Individuals who receive protein injections to treat other medical conditions may also have high RBC counts.

VII. Additional Resources

Name Web Summary
American Red Cross www.redcrossblood.org Learn which iron-rich foods can help relieve symptoms of iron-deficiency anemia.
Stanford Medicine www.scopeblog.stanford.edu Find out how to maintain healthy iron levels while following a vegetarian or vegan diet.
Cleveland Clinic www.my.clevelandclinic.org Learn more about the anemia that develops as a result of chronic disease.
MedlinePlus www.medlineplus.gov Learn more about the causes of abnormal RBC counts, in addition to information on iron supplements to relieve the symptoms of anemia.

VIII. Sources Used in This Article