Type 2 Diabetes

Key points

What it is

Type 2 diabetes is a condition where the level of glucose (sugar) in the blood stays too high over time. It is the most common form of diabetes, making up around nine in ten cases. It is closely linked to metabolic health and everyday habits. This is different from type 1 diabetes, which is an autoimmune condition with a different cause.

In type 2 diabetes, the problem is not a sudden lack of insulin. Instead, the system that uses insulin gradually stops working as well as it should. For years, the body copes and blood sugar stays normal. Type 2 diabetes is diagnosed once the body can no longer cope, then blood sugar rises too high. Type 2 diabetes is best understood as the end point of a slow process, not something that happens suddenly. This is why it can often be improved.

What causes it, and who is at risk

The underlying cause is insulin resistance. Over time, the body's cells respond less to insulin, so the pancreas makes more and more of it to keep up. Eventually, the cells that make insulin (beta cells) become overworked. Fat can also build up in the pancreas and stop the beta cells working properly. When this happens insulin can drop a bit. This combined with the insulin resistance causes blood sugar to rise.

The risk factors are the same as those for poor metabolic health generally:

• Excess weight, especially around the middle.
• Physical inactivity.
• A diet high in sugar, refined carbohydrate and ultra-processed food.
• Increasing age.
• A family history of diabetes.
• Certain ethnic backgrounds (such as South Asian, African and African-Caribbean), often at a lower body weight.
• PMOS, polyendocrine metabolic ovarian syndrome (previously called PCOS).
• A past history of gestational diabetes.
• Poor sleep and long-term stress.

Symptoms and signs

Type 2 diabetes can be present for years with few or no symptoms. When symptoms do appear, they reflect high blood sugar:

• Passing more urine than usual, especially at night.
• Increased thirst.
• Tiredness.
• Unexplained weight loss.
• Blurred vision.
• Slow-healing cuts, and frequent infections such as thrush.
• Signs of insulin resistance such as a larger waist or acanthosis nigricans (dark, velvety skin patches).

How it is diagnosed

Diagnosis is by blood test. The usual criteria are an HbA1c of 48 mmol/mol (6.5%) or above, a fasting glucose of 7.0 mmol/L or above, or a random or post-glucose-load value of 11.1 mmol/L or above. In someone without symptoms, the test is usually repeated to confirm. Your clinician interprets the result alongside your wider health and blood tests, and may check for early signs of complications at the same time.

The metabolic health perspective

Type 2 diabetes is really a marker of poor metabolic health, showing up as high blood sugar. Behind the high glucose are the same underlying problems: insulin resistance, persistently high insulin, a larger waist, and fat that has built up in the liver and pancreas.

Some research shows if the excess fat can be removed from the liver and pancreas, the problem can go into reverse: the liver recovers, the beta cells start working again, and blood sugar can return to normal. The research approach focused on achieving a large reduction in food intake, with the aim of weight loss. In the UK DiRECT trial, people who lost a lot of weight early on (around 15kg or more) had the best chance of achieving a normal blood sugar. About a third of everyone in the trial was still in remission after two years, rising to most of those who lost 15kg or more.

Full remission may not be possible for everyone, for example if the condition has been present for many years and the beta cells are more worn out. But even then, type 2 diabetes can almost always be improved a lot with the right lifestyle changes, especially cutting back on sugar and refined carbohydrate, so the body needs less insulin. Better control, fewer medicines and lower risk are all possible even without full remission.

Not everyone with type 2 diabetes is overweight, and not everyone needs to lose weight. The same approaches, lowering sugar and carbohydrate, building muscle and staying active, work well whatever your starting weight, because they tackle insulin resistance directly rather than only through weight loss.

Treatment and management

The aims are to bring blood sugar down toward normal, to relieve symptoms, to reduce the risk of long-term complications, and, where achievable, to reach remission (normal blood sugar without glucose-lowering medication). Treatment combines lifestyle change, sometimes other non-drug measures, and medication, guided and monitored by your healthcare team.

Lifestyle and the Health Foundations

This is the most effective part of treatment, and for many people it can lead to remission.

Nutrition

Reducing sugar and refined carbohydrate lowers the amount of glucose entering your blood. This means your body needs less insulin and your blood sugar stays steadier, and it helps whether or not you lose weight. Build meals around protein, non-starchy vegetables and natural fats. In practice that means at least a palm-sized portion of protein, most of the rest of the plate filled with non-starchy vegetables, and natural fats for flavour. Treat starchy carbohydrate (bread, rice, pasta, potatoes) as optional, not a fixed part of the plate. Many people with type 2 diabetes do best eating less carbohydrate overall: some feel better staying under about 130g a day, and others, especially if more insulin-resistant, do better going lower, to around 70g a day or less. Try these as starting points and adjust based on how you feel and your blood sugar readings.

Movement and building muscle

Activity lowers blood sugar directly, without needing insulin: working muscles pull glucose straight out of the blood. A walk after each meal is one of the simplest ways to blunt the rise in blood sugar you get after eating (even 10 to 15 minutes makes a measurable difference). Beyond this, building and keeping muscle through resistance exercise is especially helpful in type 2 diabetes. Muscle is the body's biggest store for glucose, so the more muscle you have and use, the more easily your body handles carbohydrate, and the lower your blood sugar tends to run. Aim to work the big muscles of the legs, back and arms two to three times a week (for example, 20 to 30 minutes covering legs, back, chest and arms) using bodyweight moves, bands or weights, at whatever level suits you. This builds muscle and helps protect against the muscle loss that can come with age and with weight loss. Breaking up long periods of sitting helps too.

Sleep and stress

Both have a strong effect on blood sugar. Poor sleep and long-term stress raise cortisol and other hormones that increase insulin resistance, which works against even the best diet. Aim for around seven to nine hours of sleep, with a regular bedtime and wake time, and cut out evening screens and caffeine if you are sleeping poorly. Build in a daily practice that reduces stress, such as a short walk, breathing exercises, or protecting time away from work pressures. Treat this as a real part of your treatment, not an optional extra.

Other non-pharmaceutical options

• Vitamin D and magnesium are worth correcting if low, with modest metabolic benefit.
• Some supplements (such as berberine) have shown glucose-lowering effects in trials, but quality varies and interactions are possible; others (cinnamon, chromium) have weak evidence. Discuss any supplement with your clinician, as some interact with diabetes medication.
• Stopping smoking is important, because diabetes already increases the risk of heart and blood vessel problems.

Medical and pharmaceutical treatments

A range of medicines are used, chosen to suit the individual.

Metformin

Metformin (usually the modified-release form, which tends to be kinder to the stomach) has long been the first medicine offered and is still usually used first. It lowers glucose and is generally well tolerated.

SGLT2 inhibitors

SGLT2 inhibitors are now usually started alongside metformin from the beginning, for almost everyone, rather than added later. This is because updated 2026 UK guidance is based on strong evidence that, as well as lowering glucose, they protect the heart and kidneys. These benefits continue even once blood sugar is well controlled, so the medicine is usually continued long-term for this reason.

GLP-1 receptor agonists

GLP-1 receptor agonists (such as semaglutide, liraglutide or dulaglutide) and the newer tirzepatide lower blood sugar and usually lead to significant weight loss. They are now used earlier and more often. People who already have heart or blood vessel disease may be offered metformin, an SGLT2 inhibitor and semaglutide together from the start. Earlier use is also recommended for people diagnosed with type 2 diabetes before age 40, or those with obesity who need further help lowering their blood sugar. A rare but serious side effect of semaglutide is sudden vision loss in one eye (a condition called NAION). Get urgent medical help if this happens to you.

Sulfonylureas and insulin

Sulfonylureas and insulin can still be effective options. They are usually kept for when other treatments have not worked or are not suitable, but carry a real risk of low blood sugar (hypoglycaemia) and weight gain. Insulin is usually started as a once- or twice-daily long-acting (basal) injection, with more complex regimens added later if needed.

Complications and outlook

Blood sugar that stays high for years can damage small blood vessels (affecting the eyes, kidneys and nerves) and large blood vessels (raising the risk of heart attack, stroke and circulation problems). This is why good control matters so much. Regular eye screening and kidney checks are a normal part of your care, because damage can build up before you notice any symptoms. If your blood sugar drops quickly after starting treatment, tell your eye screening service. A fast drop can sometimes make existing eye changes temporarily worse before things settle down.

The outlook has improved a great deal, for two reasons: better medicines that protect the heart and kidneys, and the discovery that type 2 diabetes can often be drastically improved with the right lifestyle changes. Acting early and improving your metabolic health gives you the best chance not just of controlling the condition, but of reversing it.

When to see a doctor

• See a doctor if you have symptoms suggesting diabetes, such as excessive thirst, frequent urination, unexplained weight loss, fatigue or blurred vision.
• Seek urgent help for very high blood sugar with vomiting, drowsiness, rapid breathing or confusion (these can signal a medical emergency).
• If you have diabetes, attend your regular reviews and eye, foot and kidney checks, and discuss any plan to lose weight or change your diet so medication can be adjusted safely.

Summary