My blood glucose remains in the 300–400 mg/dL range despite taking 8 units of insulin glargine (Lantus); how many additional units of insulin glargine should I increase to?

Increase Lantus by 2 units every 3 days until fasting blood sugar reaches goal

With blood glucose levels in the 300-400 mg/dL range on only 8 units of Lantus, you should increase the dose by 2 units every 3 days, monitoring fasting blood glucose closely, until you reach your target fasting glucose goal (typically <100-130 mg/dL depending on individual circumstances). 111

Titration Algorithm

The 2025 ADA Standards of Care provide a clear evidence-based titration approach for basal insulin:

• Increase by 2 units every 3 days to reach fasting plasma glucose (FPG) goal without hypoglycemia 111
• Continue this pattern until fasting glucose normalizes
• If hypoglycemia occurs without clear cause, reduce dose by 10-20% 1

Critical Context for Your Situation

Your current dose of 8 units is extremely low for someone with glucose levels of 300-400 mg/dL. The FDA label for Lantus recommends a starting dose of 10 units per day or 0.1-0.2 units/kg/day for type 2 diabetes 22. You're actually below the typical starting dose, which explains the inadequate control.

Expected Dose Requirements

Research demonstrates that basal insulin effectiveness follows a dose-response curve, with meaningful glycemic improvements typically requiring doses up to 0.5 units/kg/day 3. Beyond this threshold, additional increases yield diminishing returns with greater weight gain but no additional hypoglycemia risk. For most adults, this translates to doses ranging from 30-50+ units daily.

Important Considerations

Monitor for signs of overbasalization: If you reach doses approaching 0.5 units/kg/day (roughly 35-50 units for a 70-100 kg person) and fasting glucose improves but overall control remains poor, this signals the need for additional therapy rather than further basal insulin increases 11. Signs include:

• Large gaps between bedtime and morning glucose
• High post-meal glucose spikes
• Continued elevated A1C despite normalized fasting glucose

At these severe glucose levels (300-400 mg/dL), consider adding prandial insulin: The guidelines specifically note that glucose ≥300 mg/dL often warrants more aggressive insulin therapy, potentially including mealtime rapid-acting insulin in addition to basal insulin 4. This may be more effective than basal insulin alone.

Alternative intensification: If not already on a GLP-1 receptor agonist (like semaglutide or tirzepatide), adding one of these medications can provide substantial glucose lowering with weight loss benefits and lower hypoglycemia risk compared to insulin intensification alone 11.

Practical Implementation

1. Increase Lantus by 2 units every 3 days starting immediately
2. Check fasting blood glucose daily before breakfast
3. Target fasting glucose <130 mg/dL initially (can tighten to <100 mg/dL once stable)
4. Continue increases until fasting glucose reaches goal
5. Expect to need 30-50+ units based on your current glucose levels
6. Reassess strategy if you reach 0.5 units/kg/day without adequate control

The systematic 2-unit every 3-day increase is safe, evidence-based, and will get you to an effective dose within several weeks 15.