What is the recommended reduction in long-acting and short-acting insulin doses when starting Monjouro (medication name)?

Insulin Dose Reduction When Starting Mounjaro (Tirzepatide)

When initiating Mounjaro in patients on insulin therapy, reduce basal (long-acting) insulin by 20% and reduce prandial (short-acting) insulin by 50% if the dose is greater than 10 units per meal; if prandial insulin is 10 units or less per dose, discontinue it entirely. 1

Basal (Long-Acting) Insulin Adjustment

• Decrease the basal insulin dose by 20% at the time of Mounjaro initiation to prevent hypoglycemia 1
• This applies to all long-acting insulins including glargine, detemir, degludec, and NPH 1
• Monitor fasting glucose values over the subsequent week and titrate the basal insulin dose based on results 1
• If more than 2 fasting glucose values per week fall below 80 mg/dL (4.4 mmol/L), decrease the basal dose by an additional 2 units 1
• If 50% of fasting values exceed goal (90-150 mg/dL or 5.0-8.3 mmol/L), increase the dose by 2 units 1

Prandial (Short-Acting) Insulin Adjustment

• If prandial insulin dose is ≤10 units per meal: Discontinue the prandial insulin completely when starting Mounjaro 1
• If prandial insulin dose is >10 units per meal: Reduce the dose by 50% and continue titrating downward as Mounjaro doses are increased 1
• The goal is to eventually discontinue prandial insulin as the GLP-1 receptor agonist effect takes hold 1
• Continue to adjust prandial doses every 2 weeks based on premeal glucose monitoring (target 90-150 mg/dL or 5.0-8.3 mmol/L) 1

Monitoring Strategy

• Check fasting glucose values to guide basal insulin adjustments 1
• Monitor premeal glucose values before lunch and dinner to guide prandial insulin adjustments 1
• Assess glucose patterns every 2 weeks and adjust medications if 50% of values are above target 1
• If more than 2 premeal values per week are below 90 mg/dL (5.0 mmol/L), decrease the corresponding insulin dose 1

Rationale for These Reductions

• GLP-1 receptor agonists like Mounjaro significantly improve glycemic control through multiple mechanisms including enhanced insulin secretion, suppressed glucagon, and delayed gastric emptying 1
• The combination of insulin and GLP-1 receptor agonists substantially increases hypoglycemia risk if insulin doses are not reduced 2
• Prioritizing and maximizing noninsulin medications like Mounjaro before escalating insulin doses minimizes weight gain and hypoglycemia risk 1
• Youth with type 2 diabetes on insulin and metformin who meet glucose goals can taper insulin over 2-6 weeks by decreasing doses 10-30% every few days, demonstrating the feasibility of insulin reduction when adding other agents 1

Common Pitfalls to Avoid

• Do not wait to reduce insulin doses—make the reduction at the time of Mounjaro initiation, not after hypoglycemia occurs 1
• Do not use rapid- or short-acting insulin at bedtime during this transition period to avoid nocturnal hypoglycemia 1
• Do not continue full-dose prandial insulin when adding Mounjaro, as this dramatically increases hypoglycemia risk 1
• Monitor closely for hypoglycemia during the first 2-4 weeks as Mounjaro reaches steady state 2
• Consider using continuous glucose monitoring if available to detect hypoglycemia patterns early 2