Prekeratocytes and keratocytes are blood film findings that are suggestive of oxidative haemolysis.

Keratocytes (bite cells) are red cells with a bite-like defect in their membrane. These occur due to phagocytosis of a Heinz body (made up of denatured haemoglobin), leaving a bite in the cell.

Prekeratocytes (blister cells) are similar to keratocytes, however retain a sliver of cell membrane - leaving the cell with a defect that resembles a blister.