Type 2 Diabetes: Diagnosis, Medicines and Complications

Type 2 diabetes mellitus is a chronic metabolic disease caused by insulin resistance together with a progressive decline in insulin secretion. It is extremely common in South Asia, often develops at a younger age and lower body weight than in Western populations, and is a leading cause of heart disease, kidney failure, blindness and amputation.

Risk factors

• Overweight and central obesity.
• Physical inactivity.
• Family history.
• South Asian, African or other high-risk ethnicity.
• Increasing age.
• History of gestational diabetes.
• Polycystic ovary syndrome.
• Hypertension and dyslipidaemia.

Clinical features

Many patients have no symptoms and are found on screening. Classic symptoms include:

• thirst (polydipsia)
• passing a lot of urine (polyuria)
• tiredness and blurred vision
• recurrent infections (for example skin infections and thrush)
• slow wound healing

Some patients first present with a complication.

Diagnosis (WHO / ADA thresholds)

• HbA1c 48 mmol/mol (6.5%) or higher.
• Fasting plasma glucose 7.0 mmol/L (126 mg/dL) or higher.
• 2-hour glucose 11.1 mmol/L (200 mg/dL) or higher on an oral glucose tolerance test.
• Random plasma glucose 11.1 mmol/L (200 mg/dL) or higher with symptoms.

In someone without symptoms, an abnormal result should be confirmed with a repeat test. HbA1c is unreliable in some conditions, for example haemoglobinopathies such as thalassaemia trait, recent blood loss or transfusion, pregnancy and advanced kidney disease.

Management

Lifestyle

• Structured education.
• A healthy, balanced diet with portion control and fewer refined carbohydrates and sugary drinks.
• Regular physical activity.
• Weight loss. Significant weight loss can put type 2 diabetes into remission in some patients.

Medicines

• Metformin is usually first-line, unless it is contraindicated (for example in significant kidney impairment) or not tolerated.
• SGLT2 inhibitors (for example empagliflozin, dapagliflozin) are recommended for patients with heart failure, established cardiovascular disease, high cardiovascular risk or chronic kidney disease, because they protect the heart and kidneys.
• GLP-1 receptor agonists (for example semaglutide, liraglutide) help with weight loss and cardiovascular protection.
• Other options:
  • DPP-4 inhibitors
  • sulfonylureas (risk of hypoglycaemia)
  • pioglitazone
  • insulin, when other treatments are not enough or the patient is very symptomatic with high glucose

HbA1c targets are individualised. Around 53 mmol/mol (7%) is common, with lower or higher targets depending on the patient's age, hypoglycaemia risk and other conditions.

Cardiovascular risk reduction

• Blood pressure control.
• Statin therapy for most adults with diabetes.
• Stopping smoking.

Complications and annual review

• Microvascular: retinopathy, nephropathy and neuropathy.
• Macrovascular: coronary artery disease, stroke and peripheral arterial disease.
• Diabetic foot: ulcers, infection and amputation.
• Acute emergencies: hypoglycaemia, the hyperosmolar hyperglycaemic state, and diabetic ketoacidosis (less common in type 2).

The annual review should cover:

• HbA1c and blood pressure
• lipid profile
• kidney function and urine albumin:creatinine ratio
• retinal screening
• a foot examination with sensation testing
• smoking status

Exam pearls

• Metformin is associated with a rare risk of lactic acidosis. Review it in kidney impairment and withhold it around iodinated contrast and acute illness, as per local guidance.
• SGLT2 inhibitors can cause genital infections and, rarely, euglycaemic ketoacidosis.
• Sulfonylureas and insulin cause hypoglycaemia and weight gain.

For a complete diabetes chapter, see the endocrinology part of our Medicine Companion. See also Diabetic Ketoacidosis.

Test yourself

5 exam-style single-best-answer questions. Choose your answer, then tap “Show answer”.

1. Which HbA1c value is diagnostic of diabetes?

   1. 42 mmol/mol (6.0%)
   2. 38 mmol/mol (5.6%)
   3. 45 mmol/mol (6.3%)
   4. Any value above 40
   5. 48 mmol/mol (6.5%) or higher
   Show answer

   Answer: E. 48 mmol/mol (6.5%) or higher
   HbA1c ≥48 mmol/mol (6.5%) is diagnostic; confirm with a repeat test if no symptoms.

2. Type 2 diabetes with established heart failure. Which drug class is especially recommended?

   1. Pioglitazone
   2. Meglitinide
   3. SGLT2 inhibitor
   4. Sulfonylurea
   5. DPP-4 inhibitor
   Show answer

   Answer: C. SGLT2 inhibitor
   SGLT2 inhibitors reduce heart failure hospitalisation and protect the kidneys.

3. Why may HbA1c be unreliable in a patient with thalassaemia trait?

   1. HbA1c is only for children
   2. It measures insulin
   3. It is always accurate
   4. Haemoglobinopathies alter HbA1c measurement and red cell lifespan
   5. Thalassaemia raises glucose
   Show answer

   Answer: D. Haemoglobinopathies alter HbA1c measurement and red cell lifespan
   Haemoglobin variants, recent blood loss, transfusion and pregnancy affect HbA1c.

4. Which side effect is typical of sulfonylureas?

   1. Hypoglycaemia
   2. Genital infections
   3. Pancreatitis only
   4. Weight loss
   5. Lactic acidosis
   Show answer

   Answer: A. Hypoglycaemia
   Sulfonylureas stimulate insulin release and cause hypoglycaemia and weight gain.

5. Which is part of the annual diabetes review?

   1. Chest CT
   2. Retinal screening and foot examination
   3. Lumbar puncture
   4. Colonoscopy
   5. Bone marrow biopsy
   Show answer

   Answer: B. Retinal screening and foot examination
   Annual review includes HbA1c, BP, lipids, kidney tests, retinal screening and foot checks.

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Disclaimer

For education and exam preparation only. This is not medical advice and must not be used to diagnose or treat patients. Always follow current clinical guidelines and the advice of qualified senior colleagues.