Purpose <p>Perfluorocarbon (PFC)-based nanoemulsions (NEs) have been extensively investigated as artificial blood substitutes because of their high oxygen solubility. However, their clinical translation has been significantly hindered by poor stability during storage and administration. We reinterpreted the instability of PFC NEs from a bulk rheological perspective and established an effective additive-based stabilization strategy.</p> Methods <p>Different plasma volume expanders (PVEs) were systematically evaluated as thickening additives for PFC NEs. Long-term changes in particle size, polydispersity index, phase separation, and sedimentation behavior were analyzed, and formulation stability was quantitatively assessed using the Turbiscan analysis. Physicochemical properties relevant to intravenous administration, including osmotic pressure, viscosity, and pH, were characterized for obtaining optimized formulations. Both in vitro and in vivo safety evaluations were conducted to assess biocompatibility.</p> Results <p>Most conventional polymer-based thickeners failed to sufficiently improve the stability of PFC NEs or induce aggregation and phase separation. In contrast, the specific PVE effectively suppressed sedimentation and phase separation under long-term storage conditions. The optimized formulation maintained particle stability while exhibiting physicochemical properties comparable to those of an intravenous injection. No significant cytotoxicity or in vivo toxicity was observed in cellular or animal models.</p> Conclusion <p>The instability of PFC NEs is governed by bulk rheological properties rather than interfacial instability alone, and presents a clinically relevant stabilization strategy using PVEs. This approach provides a practical method for enhancing the clinical feasibility of PFC-based artificial blood formulations.</p>