In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan.


Poikilocytosis is the term used for abnormal-shaped red blood cells (RBCs) in the blood. Normal RBCs (also called erythrocytes) are typically disk-shaped, are thinner in the middle than in the edges, with a diameter of 6.2 to 8.2 micrometers, a thickness at the thickest point of 2 to 2.5 micrometers, and a thickness in the center of 0.8 to 1 micrometers. Poikilocytosis generally refers to an increase in abnormal-shaped red blood cells that make up 10% or more of the total red blood cells. Poikilocytes may be flat, elongated, teardrop, or crescent-shaped, or they may have point-like or thorn-like projections or may have any other abnormal feature. Their presence may provide a hematologic 'fingerprint' for identifying their underlying disease pathology.

Publication types

  • Study Guide