Type 2 Diabetes Management for OPRA: Drug Choice, Targets, Sick-Day Rules and MCQs

Diagnosis

Type 2 diabetes is diagnosed on any one of: fasting plasma glucose ≥7.0 mmol/L, HbA1c ≥6.5% (48 mmol/mol), random plasma glucose ≥11.1 mmol/L with symptoms, or a 2-hour oral glucose tolerance test result ≥11.1 mmol/L — generally confirmed with a repeat test on a separate day unless the patient is symptomatic with clearly elevated glucose. These cut-offs are periodically reviewed — confirm the current figures against the latest Therapeutic Guidelines / Diabetes Australia publication before treating them as fixed.

First-line therapy

Lifestyle modification (diet, physical activity, weight management) plus metformin is first-line for essentially all newly diagnosed patients unless metformin is contraindicated or not tolerated. Metformin is renally cleared and its use is adjusted by kidney function: contraindicated at an eGFR below 30 mL/min/1.73m², and dose-reduced (typically a maximum of 1000 mg daily) at an eGFR of 30–44 mL/min/1.73m² — always confirm the current specific cut-off and maximum dose against the AMH/product information.

Second-line therapy — comorbidity drives the choice

Once lifestyle plus metformin isn't enough to reach target, the second agent is chosen primarily by comorbidity rather than glucose-lowering potency alone:

1. Established cardiovascular disease, heart failure, or high cardiovascular risk — an SGLT2 inhibitor or GLP-1 receptor agonist with demonstrated cardiovascular benefit is generally preferred.
2. Chronic kidney disease with proteinuria — an SGLT2 inhibitor is generally preferred for its renoprotective effect, independent of its glucose-lowering action.
3. No compelling comorbidity — choice is broader (SGLT2 inhibitor, DPP-4 inhibitor, GLP-1 receptor agonist, or sulfonylurea), guided by side-effect profile, hypoglycaemia risk, cost and patient preference.

Hypoglycaemia risk by drug class

Metformin, SGLT2 inhibitors, DPP-4 inhibitors and GLP-1 receptor agonists do not typically cause hypoglycaemia on their own. The incretin-based agents (DPP-4 inhibitors and GLP-1 receptor agonists) do stimulate insulin release, but only in a glucose-dependent way — their insulin-releasing effect switches off as glucose normalises, which is why they carry minimal hypoglycaemia risk alone. Sulfonylureas act by a glucose-independent mechanism instead, stimulating insulin release regardless of the current glucose level — which is exactly why they (along with insulin itself) carry a meaningful hypoglycaemia risk. This distinction is a common OPRA scenario hinge, especially when a patient on one of these presents with sweating, tremor, or confusion.

Reading the comorbidity as the real question

As with hypertension, when an OPRA stem gives a second condition alongside diabetes, treat that comorbidity as the actual subject of the question — the "correct" second-line agent is almost always the one that also addresses the comorbidity, not simply the one with the strongest HbA1c-lowering effect.

Sick-day medication rules

During acute illness with vomiting, diarrhoea, fever or reduced oral intake, several diabetes and cardiovascular medicines are temporarily withheld because dehydration raises the risk of acute kidney injury or, for SGLT2 inhibitors, euglycaemic diabetic ketoacidosis. A commonly used memory framework (sometimes taught as "sick day medicines") covers: Sulfonylureas (hypoglycaemia risk compounds with reduced intake), ACE inhibitors/ARBs, Metformin, Diuretics, and SGLT2 inhibitors — all typically withheld until the patient is eating and drinking normally, then restarted. NSAIDs are also commonly added to this list. Insulin is a specific exception: it is usually continued (with dose adjustment) rather than stopped, since abrupt insulin cessation risks diabetic ketoacidosis in insulin-requiring patients.

Recognising and treating hypoglycaemia

Adrenergic symptoms (sweating, tremor, palpitations, hunger) typically appear before neuroglycopenic symptoms (confusion, drowsiness, seizure) as blood glucose falls. A conscious, cooperative patient is treated with fast-acting oral carbohydrate (e.g. glucose tablets or juice), followed by a longer-acting carbohydrate once glucose recovers; an unconscious or non-cooperative patient needs parenteral treatment (IM glucagon or IV glucose) rather than anything given orally.

Is metformin still first-line for everyone with type 2 diabetes?

Yes, lifestyle modification plus metformin remains first-line for essentially all newly diagnosed patients, provided metformin isn't contraindicated (e.g. severe renal impairment) or not tolerated (e.g. persistent GI side effects).

Why does heart failure or CKD change the second-line drug choice?

SGLT2 inhibitors have demonstrated benefits in heart failure and diabetic kidney disease that go beyond their glucose-lowering effect, so current guidance favours them in these patients specifically, rather than choosing purely on HbA1c-lowering potency.

Why is insulin treated differently from other diabetes medicines during sick days?

Stopping insulin abruptly in an insulin-requiring patient risks diabetic ketoacidosis, so insulin is generally continued with dose adjustment during acute illness, unlike metformin, SGLT2 inhibitors, ACE inhibitors/ARBs and diuretics, which are typically withheld until the patient recovers.