Anisocytosis means that your red blood cells (RBCs) have different sizes. RBCs are the cells that carry oxygen in your blood. They should be about the same size and shape. But sometimes, they can be too big or too small or have weird shapes. This can make it hard for them to carry oxygen and make them feel tired, breathless, and pale. This article aims to provide a comprehensive understanding of anisocytosis and its implications.

Why Anisocytosis Happens

Anisocytosis is usually a sign of another problem with your blood, such as anaemia. Anaemia means that you have low RBCs or low haemoglobin. Haemoglobin is the part of RBCs that carries oxygen. There are many kinds of anaemia, and they can affect your RBCs in different ways. Some common kinds of anaemia that can cause anisocytosis are:

  • Iron deficiency anaemia: This is when you don’t have enough iron in your blood. Iron helps make haemoglobin. You can get iron deficiency anaemia from losing blood, not eating enough iron, being pregnant, or having problems with your gut. It usually makes your RBCs smaller than normal.
  • Vitamin deficiency anaemia: This is when you don’t have enough vitamin B12 or folate in your blood. These vitamins help make RBCs. You can get vitamin deficiency anaemia from not eating enough of these vitamins, not absorbing them well, having a disease called pernicious anaemia, or taking some medicines. It usually makes your RBCs bigger than normal.
  • Hemolytic anaemia: This is when your RBCs break down too fast. This can happen because of genes, infections, diseases, drugs, or poisons. It can make your RBCs different sizes depending on how they break down.

Other blood problems that can cause anisocytosis include:

  • Myelodysplastic syndrome: This is when your bone marrow does not make good blood cells. Your bone marrow is where your blood cells are made. The myelodysplastic syndrome can make your RBCs bigger or smaller depending on the type and stage of the problem.
  • Thalassemia: This is when you inherit a problem with your haemoglobin. It can make your RBCs smaller or normal depending on the type and severity of the problem.
  • Sickle cell anaemia: This is when you inherit a problem that makes your haemoglobin change shape. It can make your RBCs look like sickles or crescents. It can make your RBCs normal or smaller depending on how much they change shape.

Some drugs that treat cancer can also cause anisocytosis by affecting the production or survival of your RBCs.

How Anisocytosis Is Found

A blood test called a complete blood count (CBC) usually finds anisocytosis. A CBC tells you how many and what kind of blood cells you have. It can also tell you if you have low haemoglobin, low hematocrit, high or low white blood cells, or high or low platelets.

A CBC may also include a number called red cell distribution width (RDW), which tells you how much your RBCs vary in size. A high RDW means that you have a lot of anisocytosis in your blood.