Hyperglycaemia occurs in the majority of critically-ill patients, partly because patients are hypercatabolic and consequently have increased glucose levels and partly because of insulin resistance. Hyperglycaemia is associated with increased mortality in critical illness. In 2001 it was shown that mortality and other complications of critical illness can be decreased by adopting ‘tight’ glycaemic control (4·1–6·4 mmol/l). The critical care world adopted tight glycaemic control enthusiastically, until it became apparent that profound life-threatening hypoglycaemia could result. Most clinicians, currently, have adopted regimens aiming to control glucose between 4 and 8 mmol/l. Practising this regimen safely requires attention to detail. Patients must be provided with energy as well as insulin; preferably via the enteral route, but parenterally if necessary. Insulin is administered according to a relatively simple scale that is adjustable by nursing staff according to patients' glucose results. Frequent glucose measurement is essential to success, along with using visual charting that makes sudden changes in blood glucose levels obvious. There are several ‘champions’ of safe implementation of glucose control in the intensive care unit at the Royal Liverpool University Hospital who are educators and who feed results back to staff regularly. Further studies will clarify the ultimate role of tight glycaemic control, but it can be done safely with meticulous attention to detail.