Causes of lactic acidosis

A discussion of the causes of a high anion gap metabolic acidosis are frequently required by the CICM SAQs, and lactate often comes up as a differential. Beyond that, there are a series of questions which ask specifically about the causes of lactic acidosis.

These questions are numerous. There is practically one in every paper.
A few specific examples include:

Many of these questions for some reason focus repetitively on the plight of a certain middle-aged diabetic with a history of alcohol abuse. A specific feature of these questions is  the use of red cell transketolase as a test of thiamine deficiency, reminding the candidates that this is an important differential.

Lactic acidosis is discussed at greater length in a series of chapters dedicated to acid-base disturbances in their various forms and permutations. In order to simplify revision,  a tabulated list of aetiologies is offered below, organised according to an increasingly irrelevant classification system from the 1980s.

Causes of Lactic Acidosis
The massively flawed Cohen-Woods classification

In order to simplify revision, I have paired these causes with helpful investigations. The college frequently asks for investigations.

Causes of Lactic Acidosis: Investigations and Clinical Features