When searching for a more suitable detection system, we discovered that reactions between ferricyanide complexes and creatinine, which were discovered in the 19 th century (Fig. ), remained relatively unexplored within electrochemical systems, despite the attractive features of ferricyanide (fast, reversible, wide electrode compatibility) for low-cost systems (Fig. ). Accordingly, we investigated the ferricyanide-mediated electrochemical detection of urinary creatinine and its implementation in paper-based FIA with two-electrode detectors. We first explored the working range and limitations of the two-electrode detectors, and then optimized their sensing performance for urinary creatinine. Finally, we demonstrated high-throughput testing of clinical urine samples using disposable cartridges and a low-cost reader.