Critically ill patients often exhibit hyperglycaemia. Although the cause of this hyperglycaemia is probably multifactorial, peripheral insulin resistance is a major contributor, similar to type 2 diabetes mellitus (T2D). There are several similarities between critical illness and T2D, including the presence of systemic inflammation and increased plasma free fatty acids (FFA), all of which may induce insulin resistance in healthy volunteers. In critical illness, elevated catecholamines, cortisol, growth hormone and glucagon may also contribute to insulin resistance.