Why is my blood glucose still high (≈330 mg/dL post‑meal, 283 mg/dL overnight, 281 mg/dL fasting) despite a basal insulin glargine (Lantus) dose of 50 units, a bolus carbohydrate ratio of 1 unit per 8 g carbohydrate, and a correction factor of 1 unit per 25 mg/dL, and what adjustments should be made?

Inadequate Basal Insulin Dosing with Insufficient Prandial Coverage

Your current regimen is fundamentally inadequate: 50 units of Lantus is providing only partial basal coverage (approximately 0.7 units/kg/day for your weight), and you have no scheduled prandial insulin to address meal-related glucose excursions—only reactive correction doses that are far too weak (1:25 correction factor) to manage blood glucose levels consistently above 280 mg/dL. 1, 2

Immediate Regimen Restructuring Required

1. Aggressive Basal Insulin Titration

• Increase Lantus by 4 units every 3 days until fasting glucose consistently reaches 80–130 mg/dL, because your fasting glucose of 281 mg/dL falls into the ≥180 mg/dL category requiring the more aggressive 4-unit increment 1, 2
• Your current 50-unit dose represents approximately 0.7 units/kg/day (assuming ~70 kg body weight), which is approaching the critical threshold of 0.5–1.0 units/kg/day where further basal escalation alone becomes counterproductive 1, 2
• Monitor daily fasting glucose and adjust every 3 days; do not wait longer, as this unnecessarily prolongs time to target 1, 2

2. Initiate Scheduled Prandial Insulin Immediately

• Start with 4 units of rapid-acting insulin (lispro, aspart, or glulisine) before your largest meal, or alternatively use 10% of your current basal dose (5 units) 1, 2
• Administer 0–15 minutes before meals for optimal postprandial control 1, 3
• Your post-meal glucose of 330 mg/dL with a 1:8 carb ratio clearly indicates this ratio is insufficient; a more typical starting ratio is 1:10–15 grams of carbohydrate per unit 1
• Titrate prandial doses by 1–2 units or 10–15% every 3 days based on 2-hour postprandial glucose readings, targeting <180 mg/dL 1, 2

3. Recalculate Your Correction Factor

• Your current correction factor of 1:25 is far too weak for blood glucose levels consistently >280 mg/dL 1, 2
• Use the formula ISF = 1500 ÷ Total Daily Dose (TDD) to calculate an appropriate correction factor 1
• With your current 50 units of Lantus plus minimal correction doses, your TDD is approximately 50–55 units, yielding an ISF of approximately 1:27–30, which is close to your current 1:25 but will need recalculation as you add prandial insulin 1
• As you add prandial insulin and increase basal doses, recalculate ISF weekly using the new TDD to maintain appropriate correction potency 4

Critical Threshold Warning: Overbasalization Risk

• When basal insulin exceeds 0.5 units/kg/day and approaches 1.0 units/kg/day, adding prandial insulin becomes more appropriate than continuing to escalate basal insulin alone 1, 2
• Clinical signals of overbasalization include: basal dose >0.5 units/kg/day, bedtime-to-morning glucose differential ≥50 mg/dL (your overnight 283 to fasting 281 shows minimal drop, suggesting inadequate basal coverage rather than excess), hypoglycemia episodes, and high glucose variability 1, 2
• Your pattern (overnight 283, fasting 281, post-meal 330) indicates both inadequate basal coverage AND absent prandial coverage, not overbasalization 1, 2

Foundation Therapy: Metformin Optimization

• Ensure you are taking metformin at maximum tolerated dose (up to 2000–2550 mg daily) unless contraindicated, as this combination with insulin provides superior glycemic control with reduced insulin requirements and less weight gain 1
• Continue metformin even as you intensify insulin therapy 1

Monitoring Requirements

• Check fasting glucose daily during basal titration 1, 2
• Check pre-meal and 2-hour postprandial glucose to guide prandial insulin adjustments 1, 2
• Reassess HbA1c every 3 months during intensive titration 1
• If hypoglycemia occurs (glucose <70 mg/dL), reduce the implicated dose by 10–20% immediately and treat with 15 grams of fast-acting carbohydrate 1, 2

Common Pitfalls to Avoid

• Do not continue escalating basal insulin beyond 0.5–1.0 units/kg/day without addressing postprandial hyperglycemia, as this leads to overbasalization with increased hypoglycemia risk and suboptimal control 1, 2
• Do not rely solely on correction insulin; scheduled basal-bolus therapy with basal, prandial, and correction components is the preferred regimen 1
• Do not discontinue metformin when intensifying insulin unless contraindicated, as this leads to higher insulin requirements and more weight gain 1
• Do not delay adding prandial insulin when blood glucose levels are consistently >250 mg/dL, as this clearly indicates the need for both basal and prandial coverage 1, 2

Expected Outcomes

• With appropriate basal-bolus therapy at weight-based dosing, you can expect HbA1c reduction of 2–3% from baseline over 3–6 months 1
• Properly implemented basal-bolus regimens achieve mean glucose <140 mg/dL in approximately 68% of patients, compared with only 38% using correction insulin alone 1, 2

Alternative: Consider GLP-1 Receptor Agonist

• Before advancing to full basal-bolus therapy, consider adding a GLP-1 receptor agonist (semaglutide, tirzepatide, dulaglutide, or liraglutide) to your basal insulin regimen 1
• This combination provides potent glucose-lowering with less weight gain and hypoglycemia risk than intensified insulin regimens alone 1
• GLP-1 receptor agonists should be considered in all patients before initiation of prandial insulin when no contraindications are present 1