The blood smear is very important for the diagnosis of megaloblastic anemia. Table 4 lists abnormalities that can be seen in megaloblastic anemia, along with some comments and images.
Table 4. Abnormalities in Megaloblastic Anemia.| Morphological Feature | Image and Comment |
| Macrocytes and Oval Macrocytes | Note: Some RBCs are larger than the nucleus of a lymphocyte, indicating macrocytosis, and many are oval—sometimes referred to as "macro-ovalocytes." |
| Hypersegmented Neutrophils | Defined as the presence of six or more lobes or at least 3% of neutrophils with at least 5 lobes. |
| Lack of Polychromasia | The cells at the arrows have polychromasia, which indicates they are reticulocytes. Very few reticulocytes are seen in megaloblastic anemia. |
| Basophilic Stippling | Occasionally seen in severe cases. |
| Howell-Jolly Bodies | Howell-Jolly bodies, composed of DNA, are typically large and can be fragmented in megaloblastic anemia. |
