Evaluation of plasma electrophoretic profiles and acute phase protein concentrations may play a valuable role in health assessment of reptiles; however, little is known about reference intervals in free-ranging eastern box turtles (Terrapene carolina carolina). The purpose of this study was to establish reference intervals of protein electrophoretic profiles and hemoglobin binding protein ([HBP] as determined by a haptoglobin assay) in free-ranging eastern box turtles and to assess any possible correlations between varying age class (adult vs. juvenile), sex (male, female, or unknown), season (spring, summer, or fall), or location (Tennessee vs. Illinois). Blood samples were obtained from 324 eastern box turtles from 2010 to 2012 at three sites in Illinois and one site in Tennessee, USA. Significant differences were observed with total protein (sex, season, state, Illinois location), albumin (age class, season, state, Illinois location), α-1 globulins (sex, season, Illinois location), α-2 globulins (sex, season, state, Illinois location), β globulins (age class, sex, season, state, Illinois location), γ globulins (sex, season, state, Illinois location), and hemoglobin binding protein (age class, sex, state, Illinois location). The use of electrophoretic profiles and acute phase proteins is a relatively new concept in reptilian medicine, and this study allowed for establishment of references intervals in the eastern box turtle and emphasized differences that occured based on age, sex, season, and location. Future research in this area can now build on these data to determine changes in population health over time or alterations due to specific environmental or disease threats.