Overview
Diabetes affects how the body regulates blood glucose (sugar). In type 1 diabetes, the immune system destroys insulin-producing cells. In type 2 diabetes, the body may not make enough insulin or may not use insulin effectively. Over time, high blood glucose can damage blood vessels and nerves.
How common is it?
Over 4.5 million people in the UK have diabetes. Type 2 accounts for around 90% of cases. A further 850,000 have type 2 diabetes but do not yet know it.
Causes and risk factors
Type 1 is an autoimmune condition unrelated to lifestyle. Type 2 develops when insulin resistance, usually driven by excess body fat, overwhelms the pancreas's ability to produce enough insulin. Genetics and environment interact.
Common risk factors
- Overweight or obesity (type 2)
- Physical inactivity (type 2)
- Family history of type 2 diabetes
- Age over 40 (type 2)
- South Asian, Black, or African-Caribbean ethnicity (lower BMI threshold)
- Previous gestational diabetes
- Autoimmune factors (type 1)
Symptoms
- Frequent urination, especially at night
- Increased thirst
- Unexplained weight loss
- Blurred vision
- Fatigue
- Slow-healing wounds and infections
- Type 1 can present with sudden severe illness (diabetic ketoacidosis)
- Type 2 is often symptom-free for years
When to see a doctor
See a doctor if you have unexplained thirst, frequent urination, and fatigue. Type 1 diabetes can cause life-threatening diabetic ketoacidosis rapidly. Call 999 if vomiting, breathlessness, and confusion develop in a person with diabetes.
Diagnosis
Diabetes is diagnosed using blood glucose tests such as HbA1c or fasting plasma glucose. Results are interpreted against accepted diagnostic thresholds and may be repeated. If type 1 diabetes is suspected, clinicians may use autoantibody and C-peptide tests to help classify the type of diabetes.
Treatments
Lifestyle changes
Some people with type 2 diabetes achieve remission after substantial weight loss, but results vary and remission can change over time. A diabetes team can help choose a safe plan and review medicines as glucose improves.
Medicines
Treatment depends on glucose levels, kidney function, cardiovascular or kidney disease, weight goals, side effects, cost, and personal preferences. Metformin is commonly used. SGLT2 inhibitors and GLP-1 medicines may offer heart or kidney benefits for selected people.
Insulin and glucose monitoring
Insulin is essential for type 1 diabetes and may be needed in type 2 diabetes when other treatments are not enough. Glucose meters, continuous glucose monitors, and pumps can support monitoring for selected people.
Self-care and lifestyle
- Eat a balanced diet with reduced refined carbohydrate and sugar content
- Achieve or maintain a healthy body weight
- Exercise at least 150 minutes per week (walking counts)
- Attend annual diabetes review for eye, kidney, and foot checks
Prevention
Type 2 diabetes can be delayed or prevented by achieving and maintaining a healthy weight, eating a balanced diet, and exercising regularly. Type 1 cannot currently be prevented.
Sources and review
Last reviewed: 11 July 2026 by the Living Diabetes Editorial Team. This guide was checked against current patient and professional guidance. It is educational and does not replace care from your own healthcare team.