What is Anisocytosis?

Anisocytosis is a condition that refers to a person having unequal sizes of red blood cells (RBC). The name anisocytosis is derived from 2 Greek words, aniso, which means unequal, and cytosis, which is used generally to describe characteristics, features and the number of cells.

Degenerative forms of RBC (red blood cells) Anisocytosis

Degenerative forms of RBC (red blood cells)

In a healthy individual, all RBCs should have an equal size when examined under a microscope to ensure they are all performing accordingly. If this is found to be otherwise, you are diagnosed with anisocytosis. [1]

The condition is not deadly on its own but is rather indicative of an underlying RBC problem in the body which could lead to other conditions like anemia. In fact, most people who are diagnosed with, say, sickle cell anemia, are also found to have anisocytosis. This is because both of these conditions originate from problems affecting the RBCs.

Why should Anisocytosis be a source of concern?

Even though an individual may not experience any deadly symptoms due to the condition, it should still be a worry to anyone. Not only because we all want our bodies to be the way they are supposed to be, but also because of the potential risk it may pose. [2]

To understand this risk, it’s important to first note the role of red blood cells. First of all, they are the most common type of cell in the human body, consisting of a quarter of all the cells you have. Their function is to transport oxygen all over the body, which they do with the help of hemoglobin which combines and binds with oxygen to create oxy-hemoglobin. Within the body tissues, the binding process is reversed, releasing oxygen for the cells to absorb. We all know that oxygen is then responsible for the production of energy to enable use function as living things.

Normal blood vs. Anemia

Normal blood vs. Anemia

To maximize the amount of oxygen they can bind to, the RBCs have a biconcave shape to increase surface area and thus the amount of oxy-hemoglobin. Ideally, all the RBCs should be of the same size to ensure a sufficient and consistent flow of oxygen throughout the blood. Any defects in size and shape of the RBCs can interrupt the smooth supply of oxygen, leading to the various symptoms of anisocytosis.


With inadequate supply of oxygen to various parts of the body due to anisocytosis, some of the following symptoms will be experienced: [3]

  • Fatigue – because the RBCs can’t provide enough oxygen, oxidation within the cells is hindered and the individual does not have enough energy. These symptoms are most notable in those who perform physical tasks, and they will often get tired very easily and feel exhausted
  • Increased heart rate – your body will try to compensate for the lack of oxygen in the cells by pumping more blood, which it does by increasing the heart rate. It’s a similar response to the one you get when exercising, but with anisocytosis, the rapid heart rate remains constant, which can cause vascular problems and lead to other related conditions
  • Breathlessness – with an increased heart rate, respiration will also rise requiring more supply of oxygen. After a while, it will turn to shortness of breath
  • Paling of the skin – blood is essential for all body cells’ functioning, including the skin. When it comes to the skin, which is the outermost layer of cells, blood capillaries become even narrower, and this makes the skin vulnerable to symptoms of anisocytosis. Because the capillaries are already very narrow, there is always a limited supply of oxygen by the RBC’s, anisocytosis exaggerates this deficiency, causing reduced skin cell function. This same effect is also notable in other such narrow capillaries like those in the eye and nails, which may also become pale.


Anisocytosis is often the result of another blood-related problem, usually anemia, which is a condition resulting from decreased RBCs in the blood. There are various causes of anemia, causing varied types of anemia, but they all lead to a decreased number of RBCs. If the cause of the anemia has got to do with the production of new RBCs in the bone marrow such as Diamond-Blackfan anemia, some of the newly created RBCs may be smaller due to inefficient production. [4]


Some other common causes of anisocytosis include: [5]

  • Vitamin deficiency – vitamins A and B12 are essential for the production of new RBCs in the bone marrow. A deficiency in these vitamins causes problems in the production of new RBCs leading to anisocytosis
  • Folic acid deficiency – folic acid is essential for the development of DNA which determines the size of the RBCs. Lack of this component causes an irregular size of produced RBCs
  • Iron deficiency – iron is the main compound in hemoglobin, which is a large part of the RBCs. A lack of enough iron will cause hemoglobin production to drop and subsequently affect the sizes of RBCs
  • Blood transfusion – if an individual receives blood from another person with a different size of RBCs, they experience temporary anisocytosis

Diagnosis and Treatment

After the initial physical examination and analysis of symptoms, anisocytosis is confirmed using blood tests and the samples examined under a microscope. What the doctors look for include: [6]

  • Mean cell volume (MCV), which is the number of RBCs, also the RBC count
  • RBC distribution width (RDW), to find the width of your RBCs

These tests will help to establish the relation of the wider cells to the narrower cells and classify the results into:

  • +1 Anisocytosis – when there are only a few irregularly sized RBCs in comparison to the average RDW
  • +2 Anisocytosis – when there are many irregularly sized RBCs

Treatment for anisocytosis will then be directed by the cause of the problem in the first place. If there is an underlying cause, such as anemia, then that condition is treated leading to the treatment of anisocytosis. On the other hand, if the anisocytosis is a problem on its own, it can be addressed mainly using supplements to increase vitamins, folic acid and iron in the diet. In some severe cases, another blood transfusion may be needed to filter the abnormal RBCs.


  1. Introduction to anistocytosis Available from:
  2. Concerns about anisocytosis Available from:
  3. Symptoms of anisocytosis Available from:
  4. Anaemia and anisocytosis Available from:
  5. Causes of anisocytosis Available from:
  6. Diagnosis and treatment of anisocytosis Available from:

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