Anisocytosis is a condition when the red blood cells are unequal in size. “Aniso” means unequal, and “cytosis” refers to the movement, features, or number of cells.

Anisocytosis itself is a nonspecific term, as there are several different ways in which cells can be unequal.

The condition is prominent in cases of iron deficiency anemia. Iron is mostly stored in red blood cells, which help carry and store oxygen in the blood. A lack of iron in the blood leads to a reduction of red blood cells.

In this article, we examine the different forms of anisocytosis, along with their symptoms and causes. We also take a look at how to treat and prevent the condition from occurring.

AnisocytosisShare on Pinterest
Anisocytosis is prominent in iron deficiency anemia and is a condition where the red blood cells are unequal in size.
Image credit: Dr Graham Beards, 2012

Anemia can be broken down into three different types: macrocytic, normocytic, and microcytic:

  • Macrocytosis: This refers to when red blood cells are larger than usual. It affects around 3 percent of the American population.
  • Normocytic anemia: This is a blood problem when a person has normal-sized red blood cells, but there is a low amount of them.
  • Microcytosis: This is when the red blood cells are smaller than usual.

Anisocytosis is when there is an increased variation in these cell sizes.

When the shape and size of red blood cells are not correct, then oxygen is not being transported around the body as efficiently as it should be.

This can lead to:

Various factors can affect the size of red blood cells and cause anisocytosis.


Share on Pinterest
Anemia is closely associated with anisocytosis.

Anemia is the most common blood disorder and affects over 3 million American people. It is also closely associated with anisocytosis.

Several things make people more at risk of having anemia:

  • a diet lacking in iron and vitamin C
  • intestinal problems
  • infections
  • pregnancy or menstruation
  • blood lossengaging in vigorous physical activity

Some chronic conditions also increase the risk, such as autoimmune diseases, kidney disease, liver disease, thyroid disease, and cancer

There are also many different types of anemia:

  • Iron deficiency anemia is the most common type of anemia. It develops when there is not enough iron in the blood and is often due to blood loss. It can also be caused by poor iron absorption from childbirth, pregnancy, and having gastric bypass surgery.
  • Vitamin deficiency anemia is caused by low levels of B-12 or folate, known as folic acid, due to a poor diet.
  • Aplastic anemia is a rare bone marrow disorder that develops when the body does not make enough blood cells. Viral infections, radiation, exposure to toxic chemicals, and drug use can cause aplastic anemia.
  • Hemolytic anemia happens when red blood cells are broken up. It can be caused by autoimmune diseases, infection, or can be inherited.
  • Sickle cell anemia is an inherited condition that affects the protein hemoglobin. Red blood cells become thick and clog small blood vessels.

Another type of anemia is pregnancy-related anemia. This type is common in pregnant women in their second and third trimester.

Many pregnant women experience mild anemia at this time, but more severe anemia can make the baby anemic. When a baby has anemia it may lead to an early birth and low-weight baby, cause more blood loss in labor, and reduce the ability to fight infection.

Other medical conditions

Certain other conditions, diseases, and syndromes can also lead to anisocytosis:

  • myelodysplastic syndrome
  • chronic liver disease
  • hemoglobin H disease
  • protein deficiency
  • thalassemia and other inherited blood disorders

Blood transfusion

Some people may develop anisocytosis after having a blood transfusion. This is due to the change in blood from the donor to recipient and is temporary.

The way to diagnose anisocytosis is with a blood smear. This will be conducted by a skilled professional, often a laboratory scientist, hematologist, or pathologist.

A blood sample is taken and then examined under a microscope to see if the cells are abnormal in shape or unequal in size.

The smear will look at a range of things, including:

  • number of red cells
  • cell volume
  • average amount of hemoglobin in each red blood cell
  • concentration of hemoglobin in each red blood cell
  • width of red cells

The results will determine what type of anisocytosis the person has. If the red blood cells are smaller than normal, this can be a sign of low iron or sickle cell anemia.

If the red blood cells are larger than normal, the cause could be a vitamin deficiency, liver disease, or a number of other conditions.

Further tests may then be required as anisocytosis can be a symptom of another underlying condition. These tests will be determined depending on what the doctor thinks the problem might be.

Share on Pinterest
Anemia may be treated by increasing the amount of iron-rich foods in the diet.

Treatment will depend on the cause of anisocytosis. It is essential that the underlying cause of the problem is identified so that correct treatment can begin.

Anisocytosis is often related to anemia, and anemia is typically caused by iron or vitamin deficiency.

The usual treatment for iron deficiency is taking iron supplements and changing the diet to increase iron levels through iron-rich foods.

The most common supplement is ferrous sulfate, which is taken as a tablet.

Iron-rich foods include:

  • dark green, leafy vegetables
  • brown rice
  • pulses and beans
  • nuts and seeds
  • meat and fish
  • tofu
  • eggs
  • dried fruit

People can also address vitamin deficiency by taking supplements and making changes to their diet.

In extreme cases of anisocytosis, a doctor may recommend a blood transfusion. This process can replace the blood containing abnormal cells with blood containing normal cells.

There are some lifestyle changes that people can make to try and avoid anisocytosis.

The main thing that a person can do is evaluate their diet to ensure they are consuming the right amount of vitamins and iron-rich foods.

Anisocytosis itself is not life-threatening. However, the underlying cause could be serious. Early diagnosis and treatment are important as a result.

Treatment and recovery will depend entirely on what is causing anisocytosis.