16 Target Cells (Codocytes)

Michelle To and Valentin Villatoro

Images show peripheral blood smears with numerous target cells present (examples are indicated by arrows). From MLS Collection, University of Alberta.

Image 1: 100x oil immersion. https://doi.org/10.7939/R3R49GR23

Image 2: 40x magnification. https://doi.org/10.7939/R3NG4H71X

Image 3. 60x oil immersion. https://doi.org/10.7939/R3R78644B


Cell Description:

Target cells adopt a “bullseye” morphology where hemoglobin is concentrated in the center and on the periphery with a colourless zone in between the two areas. Other target cells may also look folded or bell shaped.1-3


Note: The target cell membrane is thinner than normal cells.1,4


Cell Formation:

Liver Disease: membrane cholesterol concentration is reduced, decreasing the tensile strength of the membrane, resulting in target cell formation.2,3,5

Artifact: Target cell formation occurs when blood smears are made when humidity is high.1

Hemoglobinopathies: There is a uneven distribution of hemoglobin within the cell, and an increased surface area to volume ratio.1

Note: Target cells have an increased surface area to volume ratio and decreased osmotic fragility.1,3


Associated Disease/Clinical States:1,2,5

Hemoglobinopathies (Hemoglobin C Disease, Sickle cell Disease, Thalassemia, etc.)

Iron deficiency anemia

Obstructive Liver disease




1. Landis-Piwowar K, Landis J, Keila P. The complete blood count and peripheral blood smear evaluation. In: Clinical laboratory hematology. 3rd ed. New Jersey:  Pearson; 2015. p. 154-77.

2. Rodak BF, Carr JH. Variations in shape and distribution of  erythrocytes. In: Clinical hematology atlas. 5th ed. St. Louis, Missouri: Elsevier Inc.; 2017. p. 93-106.

3. Jones KW. Evaluation of cell morphology and introduction to platelet and white blood cell morphology.  In: Clinical hematology and fundamentals of hemostasis. 5th ed. Philadelphia: F.A. Davis Company; 2009. p. 93-116.

4. Bain BJ. Morphology of blood cells. In: Blood cells: a practical guide [Internet]. 5th ed. Chichester, UK: John Wiley & Sons, Ltd; 2015 [cited 2018 Jul 10]: 67-185. Available from: http://doi.wiley.com/10.1002/9781118817322

5. Turgeon ML. Erythrocyte morphology and inclusions.  In: Clinical hematology: theory and procedures. 4th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 1999. p. 99-111.


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Target Cells (Codocytes) Copyright © 2019 by Michelle To and Valentin Villatoro is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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