Macrocytosis Definition

One who would feel the need to enquire as to what is macrocytosis, must be informed of the fact that it is a condition related to the unusual enlargement of the RBC count or erythrocytes in blood, thereby leading to the deficiency of oxygen in the body. It is usually characterized by a near-constant level of haemoglobin. One may define macrocytosis by a MCV or mean corpuscular volume of more than 100 femtolitres.

Macrocytosis without anaemia is usually the most common occurrence but when macrocytosis is associated with reduced levels of haemoglobin, it is referred to as Macrocytic anaemia. One may classify Macrocytic anaemia as megaloblastic and non-megaloblastic. The former is associated with an abnormality related to the erythroblasts that is actually triggered by a poor synthesis of DNA. It is for this reason that macrocytosis is also known as megaloblastic anaemia. The non-megaloblastic form of anaemia occurs either due to insufficient or failure of the synthesis of haemoglobin but where the impairment of DNA synthesis does not take place. It may also be a case of normocytic anaemia.

Macrocytosis Symptoms

The symptoms of macrocytosis depend on the mildness or severity of the condition. Some of the most common symptoms of macrocytosis include fatigue, feebleness, and lack of concentration, dizziness, digestive problems, pallor, and breathing problems. One may also exhibit diarrhoea and constipation, bleeding gums, and swollen tongues in case of this condition.

However, severe macrocytosis may exhibit severe neurological problems leading to confusion, loss of balance, depression, dementia, and tingling or numbness. These symptoms may assume permanence if left untreated on time.

Macrocytosis Causes

The causes of macrocytosis may be basically grounded in the deficiency of folic acid and vitamin B 12 in the blood that are actually responsible for the formation of red blood cells. A more effective analysis of the causes of the same may reveal the exact causes of the same. The nutritional deficiency may actually be triggered by a hereditary problem known as Pernicious anaemia. It is in fact caused by the absence of ‘intrinsic factor’ in the body, thereby leading to poor absorption of nutrients.

Some of the hematologic causes of macrocytosis actually incur due to problems associated with the bone marrow and blood. Some of them include myelodysplasia, leukaemia, myelofibrosis, and pernicious anaemia.

Digestive or gastrointestinal problems such as Crohn’s disease and Celiac disease cause macrocytosis. Crohn’s disease is actually an inflammatory bowel disease and the latter one is caused due to severe sensitivity to gluten basically caused due to wheat and other grain deposition in the stomach.

Chronic alcoholism is considered to be a significant factor behind the occurrence of macrocytosis alcohol. Besides these, some of the other causes of macrocytosis include malnutrition in infancy, diet lacking in B12, liver problems, obstructive jaundice, and the deposition of phospholipids, reticulocytosis and hypothyroidism. One may also suffer from macrocytosis during pregnancy which may normalize slowly and steadily post-partum. Autoimmune disorders such as diabetes may also be a significant cause of the same. Undergoing chemotherapy may also cause macrocytosis as side-effect.

Severe macrocytosis may also be caused due to a chronic obstructive pulmonary disease (COPD), accelerated erythropoiesis, bacterial or parasitic infestation, and life-threatening HIV infection.

Macrocytosis Differential Diagnosis

A differential diagnosis of macrocytosis is sought for the purpose of differentiating it from the other kind of macrocytosis and other associated diseases and disorders.

The cause of macrocytosis may first be analysed by a full blood count test of a blood film. This may be followed by a bone marrow examination to make the distinction between the two kinds of macrocytosis more explicit.

Other tests that are usually referred in case of macrocytosis include normal urine tests, creatinine, urea and electrolyte test, C-methionine breath test, and a Coomb’s test.

Macrocytosis Treatment

The treatment of macrocytosis depends on the cause and severity of the condition. Effective treatment of the ailment actually lies in the treatment of the underlying diseases and disorders causing the same. Mild macrocytosis may be treated with the help of vitamin injections to compensate the loss of vitamin B12. One may also be prescribed oral and nasal supplements of vitamin B12 and a balanced diet rich in the same nutrient. Injections such as hydroxocobalamin are basically prescribed in case of severe diseases such as Crohn’s disease and celiac disease. These injections may be administered either on a short term or a long term basis depending on the cause. One may also undertake some measures for preventing the occurrence or severity of the condition such as avoiding the consumption of alcohol, and taking proper surgical aftercare measures.

All such measures shall help one avert severe complications associated with macrocytosis such as stomach polyps and cancer, which are by themselves life-threatening.


  1. Louise Welch July 3, 2011
  2. Sue Veen July 10, 2012
  3. Sue Veen February 4, 2017
  4. Jacob February 6, 2017