The acute phase response is an important component of the early reaction of the immune system to insults including infection, inflammation, trauma, neoplasia, and stress. Acute phase proteins are valuable prognostic indicators in many mammalian species but have been poorly studied in reptiles thus far. This study examined 18 paired samples from loggerhead sea turtles (Caretta caretta) for changes observed during the rehabilitation period. Analyses performed included packed cell volume (PCV), hemoglobin binding protein, and plasma protein electrophoresis. Significant differences were observed in all of the protein electrophoresis values. Notably, the concentration of hemoglobin binding protein (as determined by a haptoglobin assay) increased in conjunction with rising total protein (by refractometry) and PCV. The results indicate that this assay may have the potential to be a useful tool in assessing the health of sea turtles.