The protein/creatinine ratio was elevated at 3200 mg/g (<150 mg/g) consistent with nephrotic range proteinuria. Possible etiologies included diabetic nephropathy, amyloidosis, and IRGN given his recent septic arthritis. Complement C3 and C4 levels were ordered that resulted in a C3 being low. Cardiac MRI and amyloid studies were ordered. Here, C3 is linked to diabetic kidney disease.