Enlarged blood cells, which clinicians refer to as macrocytosis, may indicate the presence of an underlying disease or health condition, such as vitamin deficiency, hypothyroidism, increased red blood cell production, liver disease and more. Macrocytosis may also develop as the body's response to certain medications, according to Mayo Clinic. It can also stem from excess alcohol consumption.
Macrocytosis does not produce any noticeable signs or symptoms, notes Mayo Clinic, and may not even be detected until patients have a routine blood test. However, the discovery of macrocytosis should prompt further testing, as the condition usually results from other causes.
Vitamin deficiencies, specifically of folate and Vitamin B-12, produce red blood cells that are larger than normal. These underlying causes are corrected easily with dietary changes and supplements. Liver diseases can also prompt the growth of large blood cells, as can alcohol dependency. As with vitamin deficiencies, the condition corrects with the treatment of the underlying cause.
Certain medications also create large blood cells. Medicines for cancer, seizures and autoimmune conditions may cause enlarged blood cells. Macrocytosis can also arise in response to blood loss or when blood cell production suddenly increases, such as when people develop anemia.
To test for causes of macrocytosis, physicians generally perform more comprehensive blood tests or extract a portion of bone marrow for further analysis.