Complex Metabolic Acidosis: From Case Report to Systematic Approach

A 61‐year‐old woman was admitted with a severe high anion gap metabolic acidosis. Initially, this was attributed to elevated serum lactate levels due to metformin accumulation in the setting of acute kidney injury, and continuous venovenous hemofiltration was started. However, at the time serum lactate levels had normalized, a high anion gap metabolic acidosis persisted. This led to the detection of another causative factor. With this case, we would like to raise awareness of mixed acid‐base disorders and propose an approach to unmask them.