Diabetes

Diabetes is a metabolic disorder characterised by a persistently elevated blood glucose level. It arises from problems with insulin secretion (insulin deficiency), insulin action (insulin resistance) or a combination of the two (National Institute for Health and Care Excellence, 2024a; World Health Organization, 2025).

Diabetes is associated with the development of macrovascular problems (eg myocardial infarction, stroke and peripheral vascular disease) and microvascular problems (eg retinopathy, nephropathy and neuropathy). Other complications associated with diabetes include:

• periodontitis
• gastroparesis
• fatty liver disease
• erectile dysfunction
• depression
• dementia (National Institute for Health and Care Excellence, 2024a; 2024b)

An estimated 5.6 million people in the UK have diabetes, and this prevalence is increasing (Diabetes UK, 2025). Overall, 4.4 million people have a formal diagnosis of diabetes, with an additional 1.2 million thought to be undiagnosed (Diabetes UK, 2025). A further 6.4 million people are at high risk of diabetes, based on blood glucose readings indicating

Presenting symptoms of diabetes include:

• polyuria (excessive urination)
• polydipsia (excessive thirst)
• polyphagia (feeling of extreme, insatiable hunger)
• weight loss
• fatigue
• blurred vison
• recurrent infections

Symptoms tend to evolve gradually in type 2 diabetes, whereas they are typically more apparent in type 1 diabetes, often with additional symptoms and signs that reflect the onset of diabetic ketoacidosis, including: 

• vomiting
• abdominal pain
• confusion
• fruity breath smell
• deep laboured breaths (Kussmaul respiration) with signs of dehydration and shock (National Institute for Health and Care Excellence, 2024a; 2024b)

Symptoms of MODY are often mild, so diagnosis may be a chance finding from routine testing (Urakami, 2019).

If pancreatogenic diabetes is suspected, it is important to ask about gastrointestinal symptoms, as pancreatic exocrine function may also be affected. Gastrointestinal symptoms can include:

• upper abdominal pain
• steatorrhoea (too much fat in the stool)
• bloating
• weight loss (Morris and Moulik, 2024)

Pancreatic enzyme insufficiency usually predates diabetes onset

Type 1 diabetes

Type 1 diabetes is an autoimmune disorder, where antibodies are directed against the insulin-producing pancreatic beta-cells that lead to insulin deficiency, often arising in children and young people. Risk factors for type 1 diabetes include a family history of the condition or a personal or family history of other related autoimmune conditions, for example:

• thyroid disorders
• pernicious anaemia
• coeliac disease
• vitiligo
• Addison’s disease (National Institute for Health and Care Excellence, 2024b)

Type 2 diabetes

Insulin resistance is the hallmark of type 2 diabetes, and is linked to central adiposity (collection of fat around abdominal area). Insulin levels may increase initially in an attempt to overcome insulin resistance, but when this compensatory mechanism fails, hyperglycaemia (where blood sugar levels are too high) ensues. Pancreatic beta cell function declines over time and ultimately exogenous insulin may be required to optimise glucose levels.

Risk factors for type 2 diabetes include:

Type 1 diabetes

Characteristic diagnostic features of type 1 diabetes include rapid weight loss and osmotic symptoms of diabetes, often with clinical features of diabetic ketoacidosis with a random plasma glucose level >11.0 mmol/L. Ketone testing is essential if type 1 diabetes is suspected or for those with type 1 diabetes who have high glucose levels, acute illness and as part of ‘sick day advice rules’ where diabetic ketoacidosis is a possibility (National Institute for Health and Care Excellence, 2022a). 

C-peptide levels (a measure of insulin reserve) and pancreatic autoantibody testing can help determine the type of diabetes. C-peptide levels will be low in type 1 diabetes.

Type 2 diabetes

Type 2 diabetes is suspected on the finding of hyperglycaemia that may be accompanied by the clinical features (see ‘Symptoms’ above). Diagnosis can be made by:

• glycated haemoglobin (HbA1c) ≥48 mmol/mol
• fasting plasma glucose ≥7.0 mmol/L
• random plasma glucose ≥11.1

If type 1 diabetes is suspected, immediate (same-day) referral to the diabetes specialist team must be arranged (National Institute for Health and Care Excellence, 2024b).

An individualised approach to managing diabetes is advised (National Institute for Health and Care Excellence, 2022a; American Diabetes Association, 2024). An evidence-based, structured education programme that is appropriate to the individual’s circumstances should be offered at the point of diagnosis. Longer-term goals of managing diabetes are to reduce complications and improve quality of life.

Lifestyle change

Lifestyle change is fundamental to the management of type 2 diabetes. Goals should be achievable and sustainable in the context of the person’s circumstancess.

The National Institute for Health and Care Excellence (2022a) and Diabetes UK (Dyson et al, 2018) offer similar dietary advice for people with type 2 diabetes: 

• eat more wholegrains, fruit, vegetables, fish, nuts and legumes (high-fibre, low-glycaemic index sources of carbohydrates)
• eat less red and

American Diabetes Association. Diabetes care: standards of care in diabetes – 2024. 1st issue. Arlington County (VA): American Diabetes Association; 2024

Diabetes UK. Diabetes UK: know diabetes, fight diabetes. 2025. https://www.diabetes.org.uk/ (accessed 20 February 2025)

Dyson PA, Twenefour D, Breen C et al. Diabetes UK evidence-based nutrition guidelines for the prevention and management of diabetes. Diabet Med. 2018;35(5):541–547. https://doi.org/10.1111/dme.13603  

Ewald N, Hardt PD. Diagnosis and treatment of diabetes mellitus in chronic pancreatitis. World J Gastroenterol. 2013;19(42):7276–7281. https://doi.org/10.3748/wjg.v19.i42.7276 

Gupte A, Goede D, Tuite R, Forsmark CE. Chronic pancreatitis. BMJ. 2018;361:k2126. https://doi.org/10.1136/bmj.k2126  

Hattersley AT, Greeley SAW, Polak M et al. ISPAD Clinical Practice Consensus Guidelines 2018: The diagnosis and management of monogenic diabetes in children and adolescents. Pediatr Diabetes. 2018;19 Suppl 27:47–63. https://doi.org/10.1111/pedi.12772  

Lean ME, Leslie WS, Barnes AC et al. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. Lancet. 2018;391(10120):541–551. https://doi.org/10.1016/S0140-6736(17)33102-1

Lean MEJ, Leslie WS, Barnes AC et al. Durability of a primary care-led weight-management intervention for remission of type 2 diabetes: 2-year results of the DiRECT open-label, cluster-randomised trial. Lancet Diabetes Endocrinol. 2019;7(5):344–355.