Background: Type 1 diabetes mellitus (DM) is an autoimmune disease caused by the failure of pancreatic beta cells to secrete sufficient insulin. Several other autoimmune diseases that involve the endocrine glands may accompany type 1 DM. Prerenal acute kidney injury due to dehydration occurring during diabetic ketoacidosis (DKA) is a common condition that usually improves with appropriate fluid therapy management. Case Report: A 9-year-old child presented with DKA and renal failure that was resistant to treatment. Other autoimmune conditions potentially accompanying the DM were investigated and it was determined that the patient had severe hypothyroidism due to Hashimoto’s thyroiditis. The hypothyroidism was the cause of the treatment-resistant renal failure, which regressed within days of starting levothyroxine treatment. Conclusion: In addition to classic causes of renal failure in patients with diabetes, it is important to remember the potential effects of other underlying autoimmune events, such as hypothyroidism.