After increasing insulin glargine (Lantus) from 10 U to 12 U daily, when should I re‑evaluate fasting glucose that remains around 250 mg/dL?

When to Re-evaluate After Increasing Lantus from 10 U to 12 U Daily for Blood Sugars in the 250s

Re-evaluate fasting blood glucose in 3 days after increasing Lantus from 10 U to 12 U daily, and if fasting glucose remains ≥180 mg/dL, increase the dose by an additional 4 units every 3 days until reaching the target of 80–130 mg/dL. 1

Immediate Assessment and Titration Protocol

Your current 2-unit increase (from 10 U to 12 U) is insufficient for blood sugars in the 250s. The American Diabetes Association recommends increasing basal insulin by 4 units every 3 days when fasting glucose is ≥180 mg/dL, which clearly applies to your situation with glucose values around 250 mg/dL. 1, 2

Specific Titration Algorithm

• If fasting glucose ≥180 mg/dL (which 250 mg/dL certainly is): increase Lantus by 4 units every 3 days until fasting glucose reaches 80–130 mg/dL. 1, 2
• If fasting glucose 140–179 mg/dL: increase by 2 units every 3 days. 1, 2
• Target fasting glucose: 80–130 mg/dL. 1, 2
• If any glucose reading falls <70 mg/dL: immediately reduce the dose by 10–20% and treat with 15 g of fast-acting carbohydrate. 1

Why 3 Days Is the Standard Interval

Basal insulin reaches steady-state pharmacokinetics within 24–48 hours, so a 3-day period provides sufficient data to assess the true effect while avoiding day-to-day variability. 1 This interval is specifically recommended by the American Diabetes Association for all long-acting insulin adjustments. 1, 2

Monitoring Requirements During Titration

• Check fasting blood glucose every morning during the titration phase to guide dose adjustments. 1, 2
• Record all fasting glucose values to identify patterns over the 3-day intervals. 1
• Reassess the dose every 3 days while actively titrating. 1
• Continue daily monitoring until fasting glucose consistently falls within 80–130 mg/dL for at least one week. 1, 2

Critical Threshold: When to Add Prandial Insulin

When your Lantus dose approaches 0.5 units/kg/day (roughly 35–40 units for most adults) without achieving target fasting glucose, stop further basal escalation and add rapid-acting insulin before meals instead. 1 Blood sugars in the 250s likely reflect both inadequate basal coverage AND postprandial excursions requiring mealtime insulin. 1

Signs You Need Prandial Insulin (Not Just More Basal)

• Basal dose >0.5 units/kg/day without reaching targets. 1
• Bedtime-to-morning glucose differential ≥50 mg/dL. 1
• Episodes of hypoglycemia despite overall hyperglycemia. 1
• High glucose variability throughout the day. 1

Expected Outcomes with Proper Titration

• With systematic 4-unit increases every 3 days for fasting glucose ≥180 mg/dL, most patients achieve target fasting glucose (80–130 mg/dL) within 2–3 weeks. 1
• Approximately 68% of patients achieve mean glucose <140 mg/dL with properly titrated basal insulin, compared with only 38% when dosing is inadequate. 1
• Basal insulin optimization alone can produce an HbA1c reduction of 1.5–2.0%. 1

Common Pitfalls to Avoid

• Do not wait longer than 3 days between dose adjustments when fasting glucose remains ≥180 mg/dL; this unnecessarily prolongs hyperglycemia exposure and increases complication risk. 1
• Do not make 2-unit increases when fasting glucose is ≥180 mg/dL; the evidence-based algorithm specifies 4-unit increases for this range. 1, 2
• Do not continue escalating Lantus beyond 0.5–1.0 units/kg/day without addressing postprandial hyperglycemia with mealtime insulin; this leads to "over-basalization" with increased hypoglycemia risk. 1
• Never delay insulin dose adjustments based on fear of hypoglycemia when glucose is in the 250s; properly implemented titration does not increase hypoglycemia incidence. 1

Foundation Therapy Considerations

• Continue metformin at maximum tolerated dose (up to 2000–2550 mg daily) when intensifying Lantus; metformin reduces total insulin requirements by 20–30% and provides superior glycemic control. 1
• Do not discontinue metformin when increasing insulin unless specifically contraindicated. 1

Practical Next Steps

1. Today: Increase Lantus to 16 U (not 12 U) given your fasting glucose is around 250 mg/dL. 1, 2
2. Day 4: Check your 3-day average fasting glucose. If still ≥180 mg/dL, increase to 20 U. 1
3. Day 7: Reassess again. Continue 4-unit increases every 3 days until fasting glucose reaches 80–130 mg/dL. 1
4. Ongoing: Once stable, check fasting glucose daily for one week, then transition to less frequent monitoring as directed by your provider. 1

The key message: with fasting glucose in the 250s, you need aggressive 4-unit increases every 3 days—not 2-unit increases—and you should re-evaluate every 3 days until reaching target. 1, 2