HNF1B and Hypokalemia: <h4>Background</h4>Maturity-onset diabetes of the young 5 (MODY5), a rare diabetes syndrome of young adults, is associated with variants in hepatocyte nuclear factor 1B (<i>HNF1B</i>) gene.<h4>Case presentation</h4>We reported a case of MODY5, which presented with diabetic ketosis, multiple renal cysts, and hypokalemia.