Abstract

Background: Metformin-associated lactic acidosis (MALA) is a rare but fatal complication of metformin therapy, typically precipitated by acute kidney injury (AKI), dehydration, or sepsis. Natural disasters disrupt healthcare access and increase gastrointestinal illness, data on MALA within the disaster settings are limited. Case presentation: We report 12 patients presenting with severe MALA during a major flooding event in Hat Yai, Southern Thailand, in late 2025. Disrupted infrastructure led to poor oral intake, dehydration, and delayed presentation, with many patients continuing metformin despite acute illness. At presentation, patients exhibited high-anion gap metabolic acidosis (pH range 6.78–7.31, peak lactate 24 mmol/L) and advanced AKI. All patients required emergent renal replacement therapy (RRT), utilizing intermittent hemodialysis, slow low-efficiency dialysis, or continuous RRT depending on hemodynamic stability and clinical context. Timely RRT facilitated rapid biochemical correction and renal recovery. All the cohort survived to hospital discharge. Conclusions: This case series highlights flood-related healthcare disruption as an under-recognized precipitating factor for MALA. Severe MALA may occur despite therapeutic metformin dosing when acute illness, dehydration, and AKI coexist. Early recognition, prompt discontinuation of metformin, and timely initiation of RRT are critical for favorable outcomes. These findings underscore the importance of disaster-specific preventive strategies, including proactive dissemination of “sick-day rules,” early nephrology involvement, and ensuring timely access to medical care for high-risk patients during natural disasters.