Diabetes

Diabetes mellitus is a group of metabolic disorders characterised by chronic hyperglycaemia resulting from defects in insulin secretion, insulin action, or both. Type 1 diabetes is an autoimmune destruction of pancreatic β-cells producing absolute insulin deficiency. Type 2 diabetes — around 90% of UK cases — is driven by insulin resistance combined with progressive β-cell failure, and is strongly linked to overweight, physical inactivity and ageing.^{[1]Diabetes UK[2]NHS}

Diabetes UK estimates that around 5.6 million people in the UK are living with diabetes, including approximately 4.4 million diagnosed cases and an estimated 1.2 million undiagnosed — meaning about 1 in 14 people overall, rising to roughly 1 in 10 of those aged 40+. A further 6.3 million UK adults are at increased risk of developing type 2 diabetes.^{[1]Diabetes UK}

The NHS spends approximately £10 billion a year on diabetes care — around 10% of its total budget — most of it on managing complications.^{[1]Diabetes UK}

NICE guidance, aligned with WHO criteria, defines diabetes by any one of:

• HbA1c ≥ 48 mmol/mol (6.5%), or
• Fasting plasma glucose ≥ 7.0 mmol/L, or
• Random plasma glucose ≥ 11.1 mmol/L with classic symptoms, or
• 2-hour plasma glucose ≥ 11.1 mmol/L during a 75 g oral glucose tolerance test.

Non-diabetic hyperglycaemia (prediabetes) is defined in the UK as HbA1c 42–47 mmol/mol (6.0–6.4%) or fasting glucose 5.5–6.9 mmol/L — the threshold for referral into the NHS Diabetes Prevention Programme.^{[3]NICE NG28[5]NHS England DPP}

Sustained hyperglycaemia damages blood vessels and nerves, driving the major complications: cardiovascular disease, chronic kidney disease, diabetic retinopathy (the most common cause of preventable sight loss in working-age UK adults), peripheral neuropathy and lower-limb amputation. The landmark UK Prospective Diabetes Study (UKPDS) showed that each 1% reduction in HbA1c was associated with a ~21% reduction in diabetes-related deaths and a ~37% reduction in microvascular complications.^{[7]UKPDS, 1998}

The National Diabetes Audit reports how UK services perform against NICE's eight care processes (HbA1c, BP, cholesterol, BMI, smoking, creatinine, urine ACR and foot exam) and the three treatment targets — and where outcome gaps remain.^{[8]National Diabetes Audit}

England's Healthier You: NHS Diabetes Prevention Programme is the first at-scale national programme of its kind. Adults at high risk are referred to a 9-month behavioural intervention focused on diet, weight loss and physical activity. Published evaluations show clinically meaningful reductions in weight and HbA1c, and lower incidence of type 2 diabetes among completers, consistent with the trial evidence base.^{[5]NHS England DPP}

The UK DiRECT trial randomised primary-care patients with type 2 diabetes (duration ≤6 years) to a structured weight-management programme (total diet replacement followed by food reintroduction and long-term support) or usual care. At 12 months, 46% of the intervention group achieved diabetes remission — defined as HbA1c < 6.5% without glucose-lowering medication — rising to 86% among those who lost ≥15 kg. This evidence underpins the NHS Type 2 Diabetes Path to Remission programme.^{[6]DiRECT, Lancet 2018}

• Achieve and maintain a healthy weight; even 5–10% loss substantially improves glycaemia.
• At least 150 minutes per week of moderate-intensity activity, plus 2 resistance sessions (UK CMOs).
• Dietary patterns emphasising whole grains, pulses, vegetables, nuts and unsaturated fats — including Mediterranean-style and lower-carbohydrate options — are explicitly supported by NICE NG28.
• Do not smoke; stay within the 14-unit alcohol guideline; prioritise 7+ hours of sleep.
• Attend all eight annual NICE care processes — including retinal screening and foot review.

Summarised from NICE NG28 / NG17 and NHS guidance.^{[3]NICE NG28[4]NICE NG17}