Can Tresiba and Lantus Be Used Together?
No, Tresiba (insulin degludec) and Lantus (insulin glargine) should not be used together—they are both basal insulins that serve the same physiological role and combining them provides no therapeutic benefit while increasing the risk of hypoglycemia and complicating dose management. 1
Why Combining Two Basal Insulins Is Not Appropriate
- Both insulin degludec and insulin glargine are long-acting basal insulins designed to suppress hepatic glucose production between meals and overnight, providing 24-hour coverage 2
- Using two basal insulins simultaneously creates overlapping pharmacodynamic effects without addressing different glycemic needs (fasting vs. postprandial) 1
- The American Diabetes Association guidelines for combination injectable therapy specifically recommend adding either GLP-1 receptor agonists or prandial insulin to basal insulin—never a second basal insulin 1
What To Do When Basal Insulin Alone Is Insufficient
If a patient on basal insulin (whether Tresiba or Lantus) has inadequate glycemic control, the appropriate intensification strategy depends on the clinical scenario:
When Basal Insulin Dose Exceeds 0.5 units/kg/day and A1C Remains Above Target:
- Add a GLP-1 receptor agonist (preferred option): This combination provides potent glucose-lowering with less weight gain and hypoglycemia compared to intensified insulin regimens 1, 3
- Fixed-ratio combinations are available: insulin degludec/liraglutide or insulin glargine/lixisenatide 1, 3
- Alternatively, add prandial insulin doses starting with the largest meal of the day 1
When Fasting Glucose Is Controlled But A1C Remains Elevated:
- This indicates inadequate postprandial coverage—add prandial insulin or a GLP-1 receptor agonist rather than increasing basal insulin further 1, 2
- Continuing to escalate basal insulin in this scenario leads to "overbasalization" with increased hypoglycemia risk without improving A1C 2
Choosing Between Tresiba and Lantus (Not Using Both)
If switching between these agents is being considered:
- Insulin degludec has a longer duration of action (>42 hours) with more stable pharmacokinetics and less day-to-day variability than insulin glargine 4, 5, 6
- Clinical trials demonstrate insulin degludec achieves similar glycemic control to insulin glargine but with significantly lower rates of nocturnal hypoglycemia (26-59% reduction) 4, 5
- Patients experiencing recurrent nocturnal hypoglycemia on Lantus should be switched to Tresiba for superior hypoglycemia safety 2
- U-300 glargine (Toujeo) provides longer duration than U-100 glargine (Lantus) and may be considered for patients with glucose variability 2
Common Pitfalls to Avoid
- Never combine two basal insulins—this represents a fundamental misunderstanding of insulin physiology and treatment algorithms 1
- Recognize when basal insulin is optimally titrated (acceptable fasting glucose) but A1C remains elevated—this requires adding prandial coverage, not more basal insulin 1, 2
- Maintain metformin when intensifying insulin therapy, but discontinue or reduce sulfonylureas to minimize hypoglycemia risk 7, 3
- When adding GLP-1 receptor agonists to basal insulin, discontinue DPP-4 inhibitors as they are redundant 3