When to Initiate Lantus (Insulin Glargine)
Lantus should be initiated when oral medications and/or GLP-1 receptor agonists fail to achieve glycemic targets (HbA1c >7% for most adults), or immediately in patients presenting with severe hyperglycemia (HbA1c ≥9%, blood glucose ≥300-350 mg/dL, or symptomatic/catabolic features). 1
Immediate Initiation Required
Start basal-bolus insulin immediately (not just basal insulin alone) in the following situations:
- HbA1c 10-12% with symptomatic or catabolic features (weight loss, ketonuria/ketosis) 2, 1
- Blood glucose ≥300-350 mg/dL regardless of HbA1c 1
- Suspected type 1 diabetes or underweight patients 2
- Acute glycemic dysregulation during hospitalization, surgery, or acute illness 2
Standard Initiation Criteria for Type 2 Diabetes
Begin Lantus when HbA1c remains >7% despite optimal oral medications (typically metformin plus at least one additional agent) 1. The American Diabetes Association supports earlier initiation when HbA1c ≥9%, even if this means starting insulin earlier in the treatment algorithm 1.
Special Population: Youth with Type 2 Diabetes
- Start basal insulin at HbA1c >8.5% (without acidosis or ketosis) at 0.5 units/kg/day, in addition to metformin 1
Initial Dosing Strategy
For Insulin-Naive Type 2 Diabetes Patients
Start with 10 units once daily or 0.1-0.2 units/kg/day, administered at the same time each day 1. For a 50 kg patient, this translates to 10 units once daily 1.
For Severe Hyperglycemia
Consider higher starting doses of 0.3-0.4 units/kg/day when presenting with marked hyperglycemia 1.
For Type 1 Diabetes
Total daily insulin requirements typically range from 0.4-1.0 units/kg/day, with approximately 50% as basal insulin (Lantus) and 50% as prandial insulin 1. Note that 0.5 units/kg/day is typical for metabolically stable patients 1.
Titration Protocol
Increase the dose by 2-4 units every 3 days until fasting blood glucose reaches 80-130 mg/dL 1. More specifically:
- If fasting glucose ≥180 mg/dL: increase by 4 units every 3 days 1
- If fasting glucose 140-179 mg/dL: increase by 2 units every 3 days 1
- If fasting glucose <80 mg/dL on >2 occasions per week: decrease by 2 units 1
Timing of Administration
Lantus can be administered at any time of day (breakfast, dinner, or bedtime), but should be given at the same time each day for consistency 3. While traditionally given at bedtime, morning administration results in significantly fewer nocturnal hypoglycemia episodes (59.5% vs 77.5% with bedtime dosing) 3.
Critical Pitfall: Avoiding Overbasalization
Do not continue escalating basal insulin beyond 0.5-1.0 units/kg/day if HbA1c remains elevated despite controlled fasting glucose 1. This signals the need for prandial insulin addition rather than further basal insulin increases 1. Signs of overbasalization include:
- Basal dose >0.5 units/kg/day 1
- High bedtime-to-morning glucose differential (≥50 mg/dL) 1
- Hypoglycemia episodes 1
- High glucose variability 1
Foundation Therapy Requirement
Metformin should be continued when initiating or intensifying insulin therapy unless contraindicated, as it remains the foundation of type 2 diabetes therapy 1, 4.
When NOT to Delay Insulin
Delaying insulin therapy in patients not achieving glycemic goals can be harmful 1. However, with the availability of GLP-1 receptor agonists, consider GLP-1 RA before insulin initiation when no contraindications exist, as they allow lower glycemic targets with lower injection burden and reduced risk of hypoglycemia and weight gain 2.
Important Mixing Restriction
Insulin glargine should not be mixed with other forms of insulin due to the low pH of its diluent 2, 1. This requires separate injections when combining basal and prandial insulin.