Type 2 Diabetes: Diagnosis and Management — MCCQE Notes

Diagnosis

Any one of these, confirmed by a repeat test on a separate day unless the patient is symptomatic with unequivocal hyperglycaemia:

• Fasting plasma glucose ≥ 7.0 mmol/L
• HbA1c ≥ 6.5%
• 2-hour plasma glucose ≥ 11.1 mmol/L on a 75 g OGTT
• Random plasma glucose ≥ 11.1 mmol/L with classic symptoms

Prediabetes: fasting 6.1–6.9, HbA1c 6.0–6.4, or 2-hour glucose 7.8–11.0. The intervention with the best evidence is structured lifestyle change, which outperforms metformin.

HbA1c is unreliable where red cell turnover is abnormal: haemoglobinopathies, haemolysis, recent transfusion, iron deficiency, pregnancy, advanced CKD.

Targets

• HbA1c ≤ 7.0% for most adults
• ≤ 6.5% in some patients with type 2 diabetes to further reduce nephropathy and retinopathy, if it can be achieved without hypoglycaemia
• 7.1–8.5% where life expectancy is limited, hypoglycaemia unawareness is present, or in frailty and dementia — tighter is actively harmful here

Drug choice

Metformin first, unless contraindicated. Then the question is not "what lowers glucose most" but "what does this patient have":

• Established atherosclerotic cardiovascular disease → GLP-1 receptor agonist or SGLT2 inhibitor with proven benefit
• Heart failure → SGLT2 inhibitor
• Chronic kidney disease, particularly with albuminuria → SGLT2 inhibitor
• Obesity a priority → GLP-1 receptor agonist
• Cost the limiting factor → sulfonylurea, accepting hypoglycaemia and weight gain

Add these for the indication even when the HbA1c is at target.

Practical cautions: metformin is held for eGFR below 30 and around contrast; SGLT2 inhibitors cause genital mycotic infections and euglycaemic DKA (hold during acute illness, fasting and before surgery); GLP-1 agonists cause nausea and are avoided with a history of medullary thyroid carcinoma or MEN2.

Vascular protection

This is where the mortality benefit lives, and stems often reward it over glycaemic tinkering:

• Statin for anyone over 40, or with diabetes duration over 15 years, or with complications
• ACE inhibitor or ARB for hypertension, albuminuria or established cardiovascular disease
• Blood pressure target < 130/80
• Smoking cessation

Screening for complications

• Retinopathy: at diagnosis in type 2, then every 1–2 years
• Nephropathy: annual urine albumin-to-creatinine ratio and eGFR
• Neuropathy: annual 10 g monofilament testing of the feet
• Screen for depression, and ask about erectile dysfunction — both are common and under-detected