Can you take Lantus (insulin glargine) and Metformin together?

Lantus and Metformin Combination Therapy in Type 2 Diabetes

Yes, Lantus (insulin glargine) and Metformin can be safely and effectively taken together, and this combination is often recommended for patients with type 2 diabetes who cannot achieve glycemic control with metformin alone. 1, 2

Rationale for Combination Therapy

Metformin and insulin work through complementary mechanisms:

• Metformin: Decreases hepatic glucose production, improves peripheral insulin sensitivity, and reduces intestinal glucose absorption 1
• Lantus (insulin glargine): Long-acting basal insulin that provides steady insulin levels over 24 hours 2

Clinical Benefits of This Combination

1. Improved Glycemic Control:

   • Combination therapy with insulin and metformin produces glycemic control comparable to insulin alone 3
   • Metformin contributes significantly to the success of combination therapy 4

2. Insulin-Sparing Effect:

   • Patients on metformin plus insulin require lower insulin doses (13.7±6.8 vs. 23.0±9.4 U/day) 4
   • Reduces insulin requirements by approximately 17% compared to insulin alone 5

3. Reduced Weight Gain:

   • Less weight gain compared to insulin monotherapy 3
   • Metformin counteracts the weight gain commonly associated with insulin therapy 6

4. Cardiovascular Benefits:

   • Metformin may reduce risk of cardiovascular events and death 1
   • Improves cardiovascular risk factors 6

When to Consider This Combination

According to current guidelines, basal insulin (like Lantus) can be added to metformin when:

1. A1C target is not achieved after approximately 3 months on metformin monotherapy 1
2. Initial A1C is ≥1.5-2.0% above the individualized target 1
3. Blood glucose levels are ≥300 mg/dL (16.7 mmol/L) or A1C >10% 1
4. Patient has symptoms of hyperglycemia (polyuria, polydipsia) or catabolism (weight loss) 1

Practical Administration Tips

• Lantus: Typically administered once daily at bedtime 2
• Metformin: Usually given twice daily with meals (immediate-release) or once daily (extended-release) 1
• Dosing: Start with lower insulin doses when combined with metformin due to the insulin-sparing effect 4, 5

Monitoring and Adjustments

• Blood Glucose: Monitor fasting and pre-meal glucose levels
• HbA1c: Check every 3 months to assess overall control
• Hypoglycemia: Be vigilant for symptoms, especially during the first 12 weeks of combination therapy 7
• Vitamin B12: Periodic testing recommended due to potential deficiency with long-term metformin use 1

Potential Concerns and Contraindications

• Renal Function: Metformin should not be used if eGFR <30 mL/min/1.73 m² 1
• Gastrointestinal Side Effects: Metformin may cause bloating, abdominal discomfort, and diarrhea; mitigate with gradual dose titration 1
• Hypoglycemia Risk: Monitor closely, especially when initiating insulin therapy
• Lactic Acidosis: Very rare with metformin but risk increases with renal impairment 1

This combination represents a rational approach to managing type 2 diabetes when oral agents alone are insufficient for glycemic control, offering complementary mechanisms of action that address multiple aspects of diabetes pathophysiology.