Colloid osmotic pressure (COP) is an important component of the forces that manage capillary filtration and is determined by circulating plasma proteins. Patients affected by conditions resulting in hypoproteinemia often suffer severe hemodynamic derangements, including decreased COP. Because chronically debilitated sea turtles (CDT) present with severe hypoproteinemia, the objectives of this study were to 1) determine differences in plasma COP and blood analyte data (packed cell volume [PCV], sodium, chloride, plasma protein fractions) in CDT at admission compared with data from apparently healthy rehabilitated turtles at time of release (HRT) admitted from various stranding causes, and 2) to investigate correlations of COP with these selected blood analytes. COP, PCV, and most plasma protein fractions (excluding pre-albumin and γ-globulins) were significantly lower in CDT upon admission as compared with HRT. Sodium and chloride did not significantly differ between CDT and HRT. A significant increase was observed with PCV and all plasma protein fractions as COP increased. Of all protein fractions tested, albumin contributed the most toward COP (r² = 0.88, P < 0.001). The results of this study suggest that COP is significantly lower in CDT as compared with HRT, providing insight into the complexity of this critical clinical condition and a small step in advancing the understanding of associated hemodynamic imbalances. Although COP analysis is not readily available as a diagnostic test, this preliminary baseline data suggests that additional research studies are warranted, given the potential for optimization of fluid therapy during rehabilitation of CDT.