Diabetes

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?

Diabetes UK reports more than 4.7 million people diagnosed in the UK in 2024-25, with almost 1.3 million more estimated to have undiagnosed type 2 diabetes. Around 90% of diagnosed cases are type 2. These are UK estimates, not worldwide figures.

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

Arrange prompt assessment for unexplained thirst, frequent urination or weight loss, especially if symptoms develop quickly. Suspected ketoacidosis needs emergency care: warning signs include vomiting, abdominal pain, deep or rapid breathing, fruity-smelling breath, drowsiness or confusion. Do not wait for all signs or a known diabetes diagnosis. Call your local emergency number for severe symptoms, collapse, seizures or an unconscious person with suspected low blood glucose. Give nothing by mouth if swallowing is unsafe.

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

Self-care and lifestyle

• Eat a balanced diet with reduced refined carbohydrate and sugar content. If you use insulin or a sulfonylurea, learn your hypo symptoms, such as shaking, sweating, dizziness or confusion. For glucose below 4 mmol/L (72 mg/dL), if awake and able to swallow, take fast-acting sugar and recheck after 10 to 15 minutes; repeat if still low, then follow your plan for longer-acting food.
• Achieve or maintain a healthy body weight
• Exercise at least 150 minutes per week (walking counts)
• Attend regular diabetes reviews, including kidney and foot checks. Attend eye screening at the interval advised by your local programme or eye-care team.

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.