Introduction

Diabetes mellitus is a chronic disorder, characterized by raised glucose levels in blood (hyperglycaemia) and urine (glycosuria). The cause may be inherited and/or acquired deficiency of insulin production by the pancreas, or insulin resistance, where the insulin produced is ineffective. Increased blood glucose concentrations can cause structural damage, particularly to blood vessels and nerves. Microvascular complications of diabetes (diabetic retinopathy, nephropathy and neuropathy) bring problems of blindness, kidney failure, foot ulcers, gangrene and erectile impotence. However, heart disease accounts for around 50% of deaths of people with diabetes. Management involves striving to maintain blood glucose at near-normal levels through behaviour change and medication, prevention or early detection and treatment of microvascular complications and reduction of cardiovascular risk, including hypertension, lipids and weight.

There are three main forms of diabetes. Type 1 diabetes usually develops in childhood or early adulthood. The pancreas stops producing insulin, so insulin by injection or infusion pump is essential for survival. Inhaled insulin is under evaluation. Type 2 diabetes typically begins in late adulthood, though maturity onset diabetes of the young (MODY) is increasing in children. Often, though not always, associated with high body mass index, insulin production and/or the body's response to insulin declines. Management initially involves diet and exercise, perhaps with tablets to increase insulin production or uptake. In time, insulin may be required. The third form, gestational diabetes, is not considered in detail here. Diabetes prevalence is increasing rapidly worldwide, with notable ethnic differences.