Red blood cells are produced in the bone marrow and primarily transport oxygen from the lungs to the body’s tissues. They also carry carbon dioxide, a waste product, back to the lungs for exhalation. Sometimes, these cells appear larger than their typical size, which can indicate an underlying health matter. This article explains what large red blood cells signify, their causes, and how they are addressed.
What Are Large Red Blood Cells?
Large red blood cells are medically termed macrocytes, and the condition is known as macrocytosis. This characteristic is identified during a routine complete blood count (CBC) test, which measures various blood components. A specific measurement within the CBC, called Mean Corpuscular Volume (MCV), indicates the average size of red blood cells.
The MCV is expressed in femtoliters (fL). A normal MCV range for adults falls between 80 and 100 fL. An MCV value exceeding 100 fL suggests macrocytosis, meaning the red blood cells are larger than normal. This measurement helps healthcare providers understand red blood cell characteristics, although macrocytosis itself is a sign rather than a disease.
Why Red Blood Cells Become Large
Macrocytosis can arise from various factors, often stemming from issues in red blood cell production or changes in their membrane. The most frequent causes are related to nutritional deficiencies, particularly vitamin B12 and folate. These vitamins are necessary for DNA synthesis, and their deficiency impairs the proper maturation of red blood cells, leading to larger, immature cells.
Vitamin B12 deficiency can occur due to inadequate dietary intake or malabsorption issues. Folate deficiency can also result from poor nutrition or increased requirements, such as during pregnancy. Certain medications can interfere with folate metabolism, leading to a functional deficiency.
Chronic heavy alcohol consumption is another common cause of macrocytosis. Alcohol can directly affect bone marrow, interfering with red blood cell development. Additionally, alcohol use can contribute to nutritional deficiencies, including B12 and folate, due to poor absorption or inadequate dietary intake.
Liver disease can also lead to enlarged red blood cells, often due to increased cholesterol and phospholipids depositing on the red blood cell membranes, which increases their surface area. This can occur in various types of liver impairment. Hypothyroidism, an underactive thyroid, has also been linked to macrocytosis.
Certain medications can cause macrocytosis as a side effect by affecting DNA synthesis or folate metabolism. An increased number of immature red blood cells, called reticulocytes, can also result in a higher MCV. Reticulocytes are naturally larger than mature red blood cells and are released in greater numbers in response to blood loss or increased red blood cell destruction.
Recognizing Symptoms and Getting Diagnosed
Macrocytosis itself often does not produce noticeable symptoms; instead, any symptoms experienced are usually related to the underlying condition. For instance, deficiencies in vitamin B12 or folate can lead to fatigue, weakness, pale or yellowish skin, and shortness of breath. Vitamin B12 deficiency can also manifest with neurological symptoms like numbness or tingling in the hands and feet, vision problems, and memory difficulties.
The presence of large red blood cells is typically identified through a routine Complete Blood Count (CBC) test. If the MCV is elevated, further investigations are necessary to determine the specific cause. These additional tests may include measuring vitamin B12 and folate levels in the blood.
Depending on other findings, liver function tests may be conducted to assess liver health. A peripheral blood smear, where blood cells are examined under a microscope, can provide more detailed information about the appearance of the red blood cells and other blood components. In some instances, a bone marrow examination might be considered.
Addressing Large Red Blood Cells
It is important to understand that large red blood cells are an indication of an underlying issue, rather than a disease itself. Therefore, addressing macrocytosis involves identifying and treating the root cause. The approach to treatment varies based on what is causing the red blood cells to enlarge.
For nutritional deficiencies, such as low vitamin B12 or folate, treatment commonly involves supplementation. This might include oral supplements or, in cases of severe malabsorption, vitamin B12 injections. If chronic alcohol consumption is the cause, reducing or abstaining from alcohol intake is important. For liver disease, managing the liver condition is the primary focus.
When medications are the cause, a healthcare provider may consider adjusting the dosage or switching to an alternative drug. For bone marrow disorders, treatment plans can be more complex and are tailored to the specific condition. In situations involving significant red blood cell destruction or loss, the underlying cause of the rapid cell turnover needs to be managed. Consulting a healthcare professional for a thorough diagnosis and a personalized treatment plan is recommended.