Victoza to Mounjaro Dose Equivalency
There is no established direct dose equivalency between Victoza (liraglutide) and Mounjaro (tirzepatide) because they are different drug classes with distinct mechanisms of action—liraglutide is a GLP-1 receptor agonist while tirzepatide is a dual GIP/GLP-1 receptor agonist. When switching between these medications, the standard approach is to start Mounjaro at its lowest dose (5 mg weekly) regardless of the prior Victoza dose, then titrate based on glycemic response and tolerability.
Why Direct Equivalency Doesn't Exist
Tirzepatide demonstrates superior glycemic control compared to GLP-1 agonists across all dose levels. In head-to-head trials, tirzepatide 5 mg, 10 mg, and 15 mg reduced HbA1c by -2.01%, -2.24%, and -2.30% respectively, compared to semaglutide 1 mg at -1.86% 1
Liraglutide 1.2 mg reduces HbA1c by approximately -1.23% from baseline, while the maximum dose of 1.8 mg achieves slightly greater reductions 2
Even the lowest dose of tirzepatide (5 mg) produces greater glycemic improvement than maximum-dose liraglutide (1.8 mg), making traditional dose-equivalency calculations inappropriate 2, 1
Recommended Switching Protocol
Starting Mounjaro After Victoza
Initiate tirzepatide at 5 mg subcutaneously once weekly, regardless of whether the patient was on Victoza 0.6 mg, 1.2 mg, or 1.8 mg daily 1
After at least 4 weeks at 5 mg, increase to 10 mg weekly if additional glycemic control is needed 1
The maximum dose of 15 mg weekly can be used after another 4 weeks at 10 mg if further improvement is required 1
Timing Considerations
Discontinue Victoza and start Mounjaro the following day, as liraglutide has a half-life of approximately 13 hours and is administered daily 3, 4
Mounjaro is administered once weekly, providing a fundamentally different pharmacokinetic profile 1
Weight Loss Comparison
Tirzepatide produces substantially greater weight loss than liraglutide. Tirzepatide 5 mg, 10 mg, and 15 mg resulted in weight reductions of -5.38 kg, -7.13 kg, and -8.74 kg respectively, compared to baseline 2
Liraglutide at therapeutic doses (1.2-1.8 mg) produces moderate weight loss of approximately 2-3 kg 4, 2
Patients switching from Victoza to Mounjaro should expect enhanced weight loss effects, which may be desirable for most patients with type 2 diabetes 2, 1
Managing the Transition
Gastrointestinal Side Effects
Both medications cause nausea, vomiting, and diarrhea as the most common adverse effects. With tirzepatide, nausea occurs in 17-22% of patients, diarrhea in 13-16%, and vomiting in 6-10% 1
Patients previously tolerating Victoza may still experience GI symptoms when starting Mounjaro, as these are dose-dependent and medication-specific 1, 5
The gradual dose escalation protocol for tirzepatide (starting at 5 mg) helps minimize GI intolerance 1
Hypoglycemia Risk
If the patient is on a sulfonylurea or insulin, reduce these doses when initiating Mounjaro to prevent hypoglycemia, as tirzepatide has more potent glucose-lowering effects than liraglutide 6, 1
Hypoglycemia rates with tirzepatide monotherapy or with metformin are very low (0.2-1.7%), similar to liraglutide's glucose-dependent mechanism 1, 5
Monitoring After the Switch
Assess glycemic control 4-8 weeks after initiating Mounjaro to determine if dose escalation is needed 6
Monitor body weight every 4 weeks during the transition period 6
Evaluate gastrointestinal symptoms at each visit, particularly during the first 8-12 weeks when these effects are most prominent 6, 1
Key Clinical Pitfall
Do not attempt to "match" Victoza doses to Mounjaro doses based on the patient's current liraglutide regimen. The superior efficacy of tirzepatide means that even patients on maximum-dose Victoza (1.8 mg daily) should start at the lowest Mounjaro dose (5 mg weekly) and titrate upward only if additional glycemic improvement is needed 2, 1.