How should I manage a 49‑year‑old man with hypertension and type 2 diabetes mellitus who missed metformin 850 mg twice daily (BID) for two weeks and now has HbA1c 10.9% (up from 7.1% three months ago)?

Management of Metformin Non-Adherence with Severe Hyperglycemia

Immediate Action: Restart and Optimize Metformin

Restart metformin immediately at 850 mg twice daily (his previous dose) and continue indefinitely—metformin must never be discontinued when adding other agents unless contraindicated. 1, 2

• The two-week gap in metformin likely contributed significantly to the HbA1c rise from 7.1% to 10.9%, but this level of deterioration suggests the disease was already inadequately controlled on metformin monotherapy 1
• Metformin provides cardiovascular mortality benefit, reduces insulin requirements when combination therapy is needed, and carries minimal hypoglycemia risk 1, 2
• The maximum effective dose is 2000–2550 mg daily; consider increasing to 1000 mg twice daily (2000 mg total) for maximal glucose-lowering effect 1, 3
• Verify renal function (eGFR ≥30 mL/min/1.73 m²) before continuing metformin 1, 3

Add Basal Insulin Immediately

With HbA1c 10.9%, you must initiate basal insulin now—oral agents alone cannot achieve adequate control at this severity of hyperglycemia. 1, 2

• Start basal insulin (NPH or long-acting analog) at 10 units once daily at bedtime or dose 0.1–0.2 units/kg body weight 1, 2
• Titrate by 2–4 units every 3 days until fasting glucose reaches 80–130 mg/dL without hypoglycemia 1, 2
• The ADA explicitly recommends insulin initiation when HbA1c >10% or blood glucose ≥300 mg/dL because monotherapy typically lowers HbA1c by only 0.9–1.1%, which is insufficient 1, 2

Plan for GLP-1 Receptor Agonist Addition

If HbA1c remains >7% after 3 months of optimized metformin + basal insulin, add a GLP-1 receptor agonist (semaglutide, liraglutide, or dulaglutide) rather than further increasing insulin dose. 1, 2

• GLP-1 receptor agonists provide an additional 0.6–0.8% HbA1c reduction when added to existing therapy 1, 2
• They cause weight loss (2–5 kg) rather than the weight gain associated with insulin intensification 1, 2
• They carry minimal hypoglycemia risk and have proven cardiovascular benefit in patients with hypertension and diabetes 1, 2

Monitoring Protocol

• Check fasting glucose daily during insulin titration to guide dose adjustments 2
• Reassess HbA1c at 3 months—target is <7% for most adults 1, 2
• Monitor renal function annually; metformin is contraindicated if eGFR falls below 30 mL/min/1.73 m² 1, 3
• Screen for vitamin B12 deficiency periodically, especially if anemia or neuropathy develop 1

Address Adherence Barriers

• Explore why he forgot metformin for two weeks—was it truly forgetting, or were there cost, side-effect, or access issues? 2
• Simplify the regimen where possible: once-daily basal insulin at bedtime is easier to remember than multiple daily injections 1
• Consider once-weekly GLP-1 receptor agonists (semaglutide, dulaglutide) if adherence to daily medications is problematic 2

Critical Pitfalls to Avoid

• Do not delay insulin initiation while waiting for oral agents to work—at HbA1c 10.9%, combination therapy is required immediately 1, 2
• Never discontinue metformin when adding insulin; it remains foundational therapy throughout intensification 1, 2
• Avoid therapeutic inertia: if HbA1c remains >7% at 3 months, intensify therapy promptly rather than waiting another 3–6 months 1, 2
• Do not add sulfonylureas to the metformin + insulin regimen—they markedly increase hypoglycemia risk without the cardiovascular benefits of GLP-1 receptor agonists 1, 2

Expected Outcomes

• Fasting glucose should normalize to 80–130 mg/dL within 2–4 weeks of basal insulin titration 2
• Dual therapy (metformin + basal insulin) typically yields a 2–3% HbA1c reduction, potentially achieving the <7% target by 3 months 2
• If a GLP-1 receptor agonist is added at 3 months, expect an additional 0.6–0.8% HbA1c reduction with 2–5 kg weight loss 1, 2