Type 2 diabetes mellitus is a chronic metabolic condition characterised by raised blood glucose resulting from insulin resistance combined with a progressive decline in the pancreas's ability to secrete enough insulin to compensate. It accounts for the large majority of diabetes cases worldwide and is strongly associated with excess weight, physical inactivity, age, family history and certain ethnic backgrounds.
Onset is usually gradual. Some people present with the classic symptoms of thirst, frequent urination, tiredness, blurred vision and recurrent infections, but many are identified through routine blood testing or during investigation of another problem. Because glucose can be raised for years before diagnosis, complications are sometimes already present at the point the condition is confirmed.
Diagnosis is most commonly made using glycated haemoglobin (HbA1c), which reflects average glucose over roughly the preceding two to three months. A value of 48 mmol/mol (6.5%) or above is diagnostic when interpreted in the right clinical context. Fasting plasma glucose and the oral glucose tolerance test remain useful alternatives, particularly where HbA1c is unreliable, such as in pregnancy, haemoglobinopathies or significant anaemia.
Sustained hyperglycaemia damages both small and large blood vessels. Microvascular complications include retinopathy, nephropathy and peripheral neuropathy, which together drive much of the burden of sight loss, kidney failure and diabetic foot disease. Macrovascular complications include coronary artery disease, stroke and peripheral arterial disease. Structured annual review covering eyes, feet, kidneys and cardiovascular risk is central to care.
Management starts with structured education, dietary change and physical activity, with evidence that substantial weight loss can put the condition into remission for some people. Metformin remains the usual first line drug. SGLT2 inhibitors and GLP-1 receptor agonists are now widely used, not only for glucose lowering but for their demonstrated cardiovascular and renal benefits. Insulin is introduced when other agents no longer maintain control.
.svg)
