Type 2 Diabetes mellitus

What is type 2 diabetes?

Type 2 diabetes is a long-term metabolic disease in which blood glucose remains too high. Insulin, a hormone made by beta cells in the pancreas, helps glucose enter cells and regulates how much glucose the liver releases. In type 2 diabetes, insulin secretion gradually becomes inadequate, often against a background of insulin resistance.

The condition is more common in adults but can occur in children and adolescents. It is not a personal failure and it cannot be understood from body size alone. Good care can substantially reduce the risk of complications, but treatment and targets need to be individualized.

Why it develops

Type 2 diabetes develops through interacting genetic, metabolic, environmental and social factors rather than one single cause. Family history, ageing, previous gestational diabetes, polycystic ovary syndrome, prediabetes, some medicines and conditions associated with insulin resistance can raise risk. Access to nutritious food, safe places for activity, healthcare and other social circumstances can also affect risk and management.

Having overweight or obesity can increase risk for many people, but it does not make diabetes inevitable, and people at any weight can develop the condition. Risk also differs among populations and individuals. Clinicians should use person-first, non-stigmatizing assessment rather than blame.

Symptoms and when to seek help

Type 2 diabetes often causes no symptoms at first and may be found on a blood test. Possible symptoms include frequent urination, increased thirst, tiredness, blurred vision, recurrent infections, slow-healing wounds, tingling or numbness, and unintentional weight loss. Darkened, thickened skin around the neck or armpits can be associated with insulin resistance but is not diagnostic.

Seek prompt medical assessment for symptoms or a high-risk test result. Vomiting, abdominal pain, deep or difficult breathing, marked dehydration, confusion, unusual drowsiness or loss of consciousness may indicate a hyperglycaemic emergency and require the local emergency service. Do not try to diagnose diabetes with a home glucose meter.

Screening and diagnosis

Testing is based on symptoms, pregnancy and individual risk, and local guidance can differ. The American Diabetes Association’s 2026 standard recommends general adult screening from age 35 and earlier testing at any age for adults with overweight or obesity plus at least one additional risk factor. Children and adolescents need age- and risk-specific assessment. A clinician can advise when repeat testing is needed.

For a nonpregnant person, laboratory criteria for diabetes include any one of the following:

• HbA1c of 6.5% (48 mmol/mol) or higher using an appropriately standardized laboratory method;
• fasting plasma glucose of 126 mg/dL (7.0 mmol/L) or higher after at least eight hours without calorie intake;
• two-hour plasma glucose of 200 mg/dL (11.1 mmol/L) or higher during a standardized 75 g oral glucose tolerance test; or
• random plasma glucose of 200 mg/dL (11.1 mmol/L) or higher together with classic symptoms of hyperglycaemia or a hyperglycaemic crisis.

Without unequivocal hyperglycaemia, diagnosis requires two abnormal results, from the same or different tests, obtained at the same time or promptly repeated. HbA1c can be misleading when red-blood-cell turnover is altered, during some stages of pregnancy, with some haemoglobin variants and in certain illnesses; plasma-glucose testing may then be preferred. Pregnancy uses separate diagnostic pathways.

Building an individual care plan

Management aims to support daily wellbeing while reducing the risk of heart, kidney, eye, nerve and foot complications. The plan should consider age, other conditions, pregnancy plans, glucose level, hypoglycaemia risk, medicine burden, access and cost, culture and personal preferences. HbA1c and home-glucose goals are shared decisions, not one strict number for everyone.

Food, activity and weight support

There is no universal “diabetes diet” and no need to ban foods such as rice, pasta, meat or dairy for every person. A sustainable pattern commonly emphasizes vegetables, pulses, fruit, whole grains and other fibre-rich foods, appropriate protein foods and mainly unsaturated fats, while limiting sugary drinks and highly processed foods. Portions, meal timing and carbohydrate distribution can be adapted to culture, budget, medicines and glucose response. A registered dietitian or qualified diabetes professional can help where available.

Physical activity improves glucose control, cardiovascular health, strength and wellbeing. Build activity gradually according to ability, safety and preference, and reduce long periods of sitting when possible. People with heart symptoms, foot injury, advanced eye disease, neuropathy, kidney disease or medicines that can cause hypoglycaemia may need specific guidance before changing activity.

Where appropriate, respectful weight-management support can improve glucose and other health measures. Some people can achieve remission after substantial, sustained weight loss within structured care, but this is not guaranteed and ongoing follow-up remains important. Health improvements can occur without a particular weight target.

Glucose monitoring

Home finger-stick testing or continuous glucose monitoring is useful for some people, especially those using insulin or medicines that can cause hypoglycaemia. The method and frequency depend on treatment, risk and what action will be taken from the result. The diabetes team should teach technique, targets and what to do about high or low readings; monitoring is not automatically required in the same way for everyone.

Medicines

Glucose-lowering medicine is chosen with the individual, then reviewed for benefit, side effects, burden and affordability. Metformin remains a commonly used medicine, while SGLT2 inhibitors, GLP-1 receptor agonists and other classes may be preferred or added in selected circumstances. Heart or kidney disease, heart-failure risk, body-weight goals, hypoglycaemia risk, pregnancy, kidney and liver function, local eligibility and cost can all change the best choice. Some SGLT2 inhibitors and GLP-1 receptor agonists have proven heart or kidney benefits for selected people, beyond their effect on glucose.

Insulin may be used temporarily or long term when there is severe symptomatic hyperglycaemia, during acute illness or pregnancy, or when other treatment does not meet an individualized goal. Needing insulin does not mean that a person has failed. Because insulin and some tablets can cause hypoglycaemia, starting or changing treatment requires education and follow-up. Do not begin, stop or adjust diabetes medicine from a general article.

Preventing and detecting complications

Type 2 diabetes increases the risk of cardiovascular disease, stroke, kidney disease, retinal damage, nerve damage, foot ulcers and some oral and hearing problems. These outcomes are not inevitable. Risk reduction extends beyond glucose and can include blood-pressure and cholesterol management, avoiding tobacco, taking appropriate medicines and attending follow-up.

Regular care may include kidney tests, retinal screening, foot and nerve assessment, blood-pressure and lipid review, dental care and relevant vaccination. Frequency depends on local guidance and the person’s results. Check feet regularly if advised and seek prompt care for a blister, cut, colour change, swelling or wound—especially when sensation is reduced. Sudden visual change, chest pain, stroke symptoms or a severely unwell state needs urgent assessment.

Reducing risk and delaying type 2 diabetes

Type 2 diabetes cannot always be prevented. For people at increased risk, onset can often be delayed through an accessible nutritious eating pattern, activity suited to ability, adequate sleep, tobacco avoidance and structured support. Clinicians may also consider medicine for prevention in selected high-risk people. Previous gestational diabetes and prediabetes are reasons for ongoing testing and support rather than blame.

Early diagnosis and consistent follow-up matter because symptoms may be absent. A practical plan developed with a healthcare team can adapt as health, treatment, priorities and access change.