What Is Microcytosis?

  • Ayesha JamilBachelors of Biomedical Sciences with Honors - University of Nottingham, Malaysia
  • Foram SanghaviMaster of Science - MS, Oncology and Cancer Biology, Queen Mary University of London, UK

Blood is the only tissue in our body that flows. To the naked eye, blood looks like red liquid. However, when we take a closer look, we realise that all is not as it seems, for blood is made up of many important components, and the most important component of the blood is the red blood cell (RBC). If this component gets altered in any way, it can lead to worrying consequences.1

One way in which these Red blood cells alter is in the condition called microcytosis. This is when the cells are not able to function at full capacity, which can lead to a decline in the quality of life.

But how does this all come about? How do we overcome this, and what may be the root cause of it all? To understand all of that, we need to learn about the basics first.


Microcytosis (also known as microcytic Hypochromic Anemia) is a medical condition that is characterized by the presence of unusually small red blood cells (RBCs) in the blood. For these cells to function at their best, their size and shape are crucial. Red blood cell counts that fall outside of the normal range can have a number of negative effects on health as they impair the transport of oxygen.2

Given that microcytosis is frequently associated with a number of underlying conditions, its presence may be a crucial indicator of potential medical issues. Despite the fact that it can be a worrying finding, it's crucial to keep in mind that microcytosis is merely a symptom of a more serious illness rather than a disease in and of itself. Understanding the causes and 

consequences of microcytosis can aid in spotting and promptly addressing any potential health issues.2

Understanding red blood cells (RBCs)

Every tissue and organ in our body receives oxygen through the help of these amazing cells, which ensure they get the oxygen that they need to function properly and stay alive.1

To accomplish this vital task, RBCs have been carefully crafted in both their structure and function for optimum performance. Red blood cells typically have a concave shape on both sides and are shaped like biconcave discs. Because of their unusual shape, which increases their surface area, oxygen exchange is more effectively accomplished. Additionally, mature RBCs' lack of a nucleus gives more room for the protein haemoglobin, which binds to oxygen, increasing their ability to carry oxygen.

The essential part of red blood cells, called haemoglobin, is in charge of storing and carrying oxygen. With the capacity to carry up to four oxygen molecules per haemoglobin molecule, RBCs are able to move a large amount of oxygen around the body.3

In order to maintain a healthy balance, the body's intricate mechanisms control the generation and lifespan of red blood cells. Continuous removal of damaged or old RBCs from circulation by the macrophages in the spleen and liver and replacement of these with fresh ones that get made in the bone marrow is maintained for optimum functionality.1

Iron is a crucial component in the creation of healthy red blood cells, which is also why the body tightly regulates iron so that only the least amount may be lost. The body cannot produce enough RBCs without adequate levels of iron, which can result in conditions like iron deficiency anaemia. Iron is an essential component of haemoglobin.1

Definition and causes of microcytosis

Definition of microcytosis

Let's explore the world of microcytosis now that we have a better understanding of red blood cells (RBCs) and their significance in oxygen transport. Red blood cells that are too small for their normal size are referred to as microcytosis in medicine. This shrinkage can be caused by a number of underlying factors, some of which are connected to the development and maturation of these important cells.2

Common causes of microcytosis4, 5

  1. Iron deficiency anaemia
  2. Thalassemia (genetic disorder)
  3. Chronic diseases
  4. Lead poisoning

Diagnosis of microcytosis2

Blood tests to detect microcytosis

Complete blood count (CBC)

An ordinary blood test called a complete blood count, which includes red blood cells, white blood cells, platelets and many more, can reveal important details about the various elements of your blood.

Mean corpuscular volume (MCV)

An MCV blood test measures the average size of your red blood cells.

Red cell distribution width (RDW)

An RDW test measures the differences in the volume and size of your red blood cells.

Blood smear examination

A microscopic examination of a thin layer of your blood is called a blood smear. The size, shape, and appearance of your red blood cells can be examined more closely thanks to this test. An expert in the laboratory can recognize microcytosis and evaluate any anomalies that might indicate particular causes.

Additional tests to determine the underlying cause

Iron studies

Your doctor may prescribe extra tests to check your iron level, ferritin, and total iron-binding capacity (TIBC) to determine whether an iron deficiency is the root cause of microcytosis. These tests aid in determining how much iron is present in your blood and whether it is available for the synthesis of haemoglobin.6

Hemoglobin electrophoresis

A haemoglobin electrophoresis test might be carried out if thalassemia or other genetic disorders are suspected. With the aid of this test, different haemoglobin subtypes can be distinguished, and thalassemia-specific abnormal haemoglobin chains can be found.7

Clinical significance of microcytosis

Signs and symptoms

  • Fatigue
  • Weakness
  • Shortness of breath
  • Pale skin
  • Anemia

Treatment and management2

Treatment options for microcytosis

Iron supplementation

Iron supplementation is a frequent treatment for microcytosis when iron deficiency is the main contributing factor. Replenishing the body's iron reserves and promoting the production of healthy red blood cells entails ingesting iron supplements. Depending on each patient's needs, medical professionals may suggest particular dosages and formulations.

Blood transfusions

Blood transfusions may be required in severe cases of microcytosis, particularly when the condition is accompanied by illnesses like thalassemia or advanced iron deficiency anaemia. The number of healthy red blood cells can be quickly increased through transfusions, which can also help with symptoms related to the transport of oxygen.

Management of underlying conditions

If an underlying medical condition is the cause of microcytosis, treating that condition becomes essential. According to the specific diagnosis, managing gastrointestinal problems or chronic inflammatory disorders, for example, may require medication, a change in lifestyle, or other therapies.

Follow-up care and monitoring

It's very important to keep track of how well the medication prescribed is working and how the underlying condition is developing. Medical professionals such as your doctor can monitor progress and modify the treatment plan as necessary with the help of routine follow-up appointments.

It is important to emphasize that self-diagnosis and self-treatment should be avoided because successful management of microcytosis depends on a clear understanding of its cause. Healthcare professionals are qualified to diagnose and suggest personalized treatment plans based on patient needs and medical history.


The condition where red blood cells are abnormally small is regarded as microcytosis and is a significant indicator of underlying medical conditions that need to be addressed. It is crucial to comprehend the clinical significance of microcytosis because it can point to possible problems with oxygen transport and the body's iron stores. The key to enhancing general health and well-being is early detection and effective management.

The most frequent causes of microcytosis are genetic diseases like thalassemia and iron deficiency. In contrast to genetic conditions, which may call for specialized care and genetic counselling, iron deficiency can be treated through dietary changes and iron supplementation.

Blood tests, such as a complete blood count (CBC) and a blood smear analysis, are used to diagnose microcytosis. In order to pinpoint the root cause precisely, additional tests may need to be conducted, such as haemoglobin electrophoresis and iron studies.

Finally, being aware of microcytosis enables people to actively participate in their health. Individuals can work with healthcare professionals to address the underlying cause and enhance their red blood cell health by being aware of the potential implications of this condition and seeking prompt medical attention. Promoting optimum health and quality of life involves regular monitoring, preventive measures, and lifestyle considerations.


Is microcytosis serious?

Microcytosis causes microcytic anaemia, which may be a sign of an underlying medical condition. If it is left untreated, it may lead to serious medical complications that can endanger the individual's health.

How do you treat microcytosis?

Treatment depends on the underlying cause, which is why the treatment is tailored to an individual’s needs.


  1. Dean L. Blood and the cells it contains [Internet]. National Center for Biotechnology Information (US); 2005 [cited 2023 Aug 4]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK2263/
  2. Chaudhry HS, Kasarla MR. Microcytic hypochromic anemia. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Aug 4]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK470252/
  3. Ahmed MH, Ghatge MS, Safo MK. Hemoglobin: structure, function and allostery. In: Hoeger U, Harris JR, editors. Vertebrate and Invertebrate Respiratory Proteins, Lipoproteins and other Body Fluid Proteins [Internet]. Cham: Springer International Publishing; 2020 [cited 2023 Aug 4]. p. 345–82. Available from: http://link.springer.com/10.1007/978-3-030-41769-7_14
  4. Massey AC. Microcytic anemia. Differential diagnosis and management of iron deficiency anemia. Med Clin North Am [Internet]. 1992 May;76(3):549–66. Available from: https://pubmed.ncbi.nlm.nih.gov/1578956/
  5. Knollmann-Ritschel BEC, Markowitz M. Lead poisoning. Acad Pathol [Internet]. 2017 Jul 24 [cited 2023 Aug 4];4:2374289517700160. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5528905/
  6. Bouri S, Martin J. Investigation of iron deficiency anaemia. Clin Med [Internet]. 2018 Jun [cited 2023 Aug 4];18(3):242–4. Available from: https://www.rcpjournals.org/lookup/doi/10.7861/clinmedicine.18-3-242
  7. Old J, Harteveld CL, Traeger-Synodinos J, Petrou M, Angastiniotis M, Galanello R. Haemoglobin pattern analysis [Internet]. Thalassaemia International Federation; 2012 [cited 2023 Aug 4]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK190579/
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Ayesha Jamil

Bachelors of Biomedical Sciences with Honors - University of Nottingham, Malaysia

Ayesha is a passionate graduate who is highly motivated to do her best in all that she tries. functioning in a multicultural university society on campus, she has developed many skills including communication, leadership skills, and developed a strong work ethic to name a few while in university.

She was the course representative for all three of her academic years working closely with the teaching and management staff to ensure the needs and voices of her fellow students were heard as well as the implementation of any new protocol for the students that may have been introduced for them.

She has also undertaken many key roles as well as been a part of the volunteering fellows. She has taken another step towards the future by undertaking an internship with Klarity as a writer for medical articles.

my.klarity.health presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
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