Pyogenic flexor tenosynovitis (FTS) is a rapidly progressing infection of the flexor tendon sheath synovial fluid. Bacterial seeding most often occurs from trauma overlying the sheath followed by swift proximal propagation. FTS is an uncommon but high morbidity disease that emergency physicians must identify early to prevent devastating complications such as tendon rupture, digit necrosis, and sepsis. Here, we report a case of FTS that occurred in an immunocompetent 82-year-old female approximately 48 h after a fingerstick glucose test.