A 30-year-old obese male patient had been diagnosed with diabetes mellitus due to acute hyperglycemia and ketonuria. He also presented with severe hypertriglyceridemia and high levels of serum lipase. He was initially misdiagnosed with type 1 diabetes and treated with insulin for one month. At two months from first presentation, pancreatic antibodies were negative, and the C-peptide level was normal. A1c level was 5.9% without insulin treatment. The association between diabetes mellitus and acute pancreatitis is well established. We reported a case of severe transient hyperglycemia during mild acute pancreatitis in a metabolically ill patient.