SAT-535 A Case of Metformin Toxicity and Lactic Acidosis in a Patient with Acute Kidney Injury: The 'Chicken or Egg' Dilemma

Abstract Disclosure: R. Pendyala: None. C. Basaleli: None. Y. Jamal: None. Background: Metformin is a first-line treatment for type 2 diabetes mellitus (T2DM), but its use can lead to metformin-associated lactic acidosis (MALA), a rare but potentially fatal condition, especially in patients with renal impairment. MALA is characterized by elevated lactate, metabolic acidosis, and multi-organ dysfunction. In renal dysfunction patients, these signs may overlap with conditions like sepsis or heart failure, complicating diagnosis. This case highlights the challenges in early recognition and management of metformin toxicity in a patient with multiple comorbidities. Case Description: A 65-year-old male with hypertension, hyperlipidemia, stroke, and T2DM, presented with 3 weeks of abdominal pain, nausea, and vomiting. On arrival, he was lethargic, unable to protect his airway, and required intubation. Labs showed a lactate of 20 mmol/L (normal <1.8), creatinine 14.9 mg/dL (normal <1.3), and metformin level of 28 µg/mL, indicating severe metformin toxicity with lactic acidosis. Metformin levels > 5 mcg/mL are typically associated with MALA. A CT scan revealed a 4.6 cm renal mass and mild obstructive uropathy, with outpatient follow-up per urology. The patient underwent emergent dialysis with bicarbonate supplementation and vasopressor therapy. Renal function improved (creatinine decreased to 1.92 mg/dL), urine output increased, and lactate levels cleared, resulting in acidosis improvement. Discussion: This case illustrates the challenges of diagnosing and managing metformin toxicity in patients with renal dysfunction. The ambiguity between whether acute renal failure triggered metformin toxicity or vice versa poses a "chicken or egg" dilemma, common in patients with acute and chronic kidney conditions. Symptoms of metformin toxicity, particularly lactic acidosis, can be nonspecific, overlapping with other renal dysfunction-related conditions. Common signs like nausea, vomiting, abdominal pain, and altered mental status can mimic uremia or other metabolic disturbances in renal failure. Impaired renal function slows metformin elimination, increasing the risk of toxicity. The long half-life of metformin in renal impairment further heightens toxicity risks and complicates early diagnosis, especially as metformin serum levels may not always be available. MALA typically progresses insidiously, from vague symptoms like nausea and altered mental status to severe respiratory distress, hypotension, and acidosis. Treatment focuses on early recognition, dialysis to clear metformin and lactate, and correcting acidosis. In this case, a renal mass and obstructive uropathy further complicated the management, but these issues were addressed with urology consultation. This case emphasizes the importance of a multidisciplinary approach, where timely intervention can improve outcomes, even in critical cases. Presentation: Saturday, July 12, 2025