Which blood disorder is characterized by red blood cells that are larger than normal?

Megaloblastic anemia is characterized by the presence of abnormally large red blood cells, known as megaloblasts, which occur due to a deficiency in vitamin B12 or folate. These larger cells are not produced effectively by the bone marrow, resulting in a decreased ability to transport oxygen in the body.

This condition often stems from nutritional deficiencies but can also be caused by certain medications or conditions that impair absorption. The larger size of the red blood cells is a hallmark of the disorder, distinguishing it from other types of anemia where red blood cell sizes may be normal or decreased. In contrast, the other disorders mentioned tend to involve different mechanisms and characteristics, making megaloblastic anemia unique in its presentation.