Patients with type 2 diabetes who switched directly from GLP-1 receptor agonists to tirzepatide 5 mg experienced further HbA1c reduction (-0.43%), weight loss (-2.15 kg), and acceptable side effects over 12 weeks.
HbA1c dropped 0.43% in just 12 weeksPatients who were already on stable GLP-1 therapy achieved an additional HbA1c reduction of 0.43% after switching to tirzepatide — a meaningful improvement on top of their existing treatment gains.
What the researchers found
In participants switching from stable GLP-1 RA treatment to tirzepatide 5 mg:
- HbA1c decreased by -0.43% at 12 weeks (p<0.01)
- Fasting serum glucose decreased by -7.83 mg/dL (p<0.01)
- Body weight decreased by -2.15 kg (p<0.01)
- Improvements occurred across all baseline GLP-1 RA subgroups (semaglutide, dulaglutide, liraglutide)
- 13.2% (20 participants) developed gastrointestinal events
- 2% (3 participants) discontinued due to adverse events
- No severe hypoglycemia or deaths
Baseline characteristics: mean age 58.3 years, HbA1c 7.39%, BMI 35.18 kg/m², T2D duration ~12.4 years, 55% female. Most were switching from semaglutide 1.0 mg (55%) or dulaglutide 1.5 mg (42%).
Why it matters
As millions of patients are already on GLP-1 drugs, clinicians frequently face the practical question: should patients switch to tirzepatide, and how? This study provides the first prospective data showing that a direct switch to tirzepatide's starting dose provides additional metabolic benefits beyond what GLP-1 monotherapy achieves, with a manageable side effect profile. This directly informs clinical decision-making for the growing population on incretin-based therapies.
How the study worked
Prospective, open-label study enrolling adults ≥18 years with T2D (HbA1c 6.5-9.0%, BMI ≥25 kg/m²) on stable GLP-1 RA doses for ≥3 months. Participants were switched directly to tirzepatide 5 mg. Primary endpoint was HbA1c change at 12 weeks. Secondary endpoints included fasting glucose, body weight, and continuous glucose monitoring metrics. Safety was assessed throughout.
What this study cannot tell us
This is an open-label study without a comparator group of patients continuing their GLP-1 RA, so it's impossible to separate the effect of switching to tirzepatide from natural disease progression or placebo effects. The 12-week follow-up is relatively short. Most participants switched from moderate GLP-1 RA doses — results may differ for those on maximum doses. The study was industry-sponsored (Eli Lilly, which manufactures tirzepatide).
How to read the evidence
This is a prospective open-label study without a control group, placing it below randomized controlled trials in evidence strength. While the prospective design and standardized endpoints are strengths, the lack of a comparator arm and industry sponsorship (Eli Lilly) warrant cautious interpretation.
When this study was published
Published in 2024, this study addresses a highly current clinical question as tirzepatide adoption accelerates and many patients consider switching from existing GLP-1 drugs.
The bigger picture
This study addresses a real-world clinical scenario emerging from the rapid evolution of incretin-based therapy. As dual and triple agonists become available, understanding switch strategies from existing GLP-1 drugs is critical. The finding that starting tirzepatide at 5 mg (without titration from 2.5 mg) is well tolerated in GLP-1-experienced patients simplifies the transition and suggests these patients have already adapted to GLP-1 receptor stimulation.
Questions still open
- Would patients on maximum-dose semaglutide (2.0 mg) also benefit from switching to tirzepatide, or have they already maximized incretin-pathway benefits?
- Do the metabolic benefits of switching continue to grow beyond 12 weeks as tirzepatide is titrated to higher doses?
- Is the direct switch to 5 mg (skipping the 2.5 mg titration) safe and tolerable for all GLP-1-experienced patients, including those on lower doses?
Common questions
Why switch from semaglutide to tirzepatide?
Do you need to start tirzepatide at the lowest dose when switching from a GLP-1 drug?
Read the original research
Switching to Tirzepatide 5 mg From Glucagon-Like Peptide-1 Receptor Agonists: Clinical Expectations in the First 12 Weeks of Treatment.
Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists, 30(8), 701-709
Citation
Jabbour, Serge; Paik, Jim S; Aleppo, Grazia; Sharma, Palash; Gomez Valderas, Elisa; Benneyworth, Brian D. (2024). Switching to Tirzepatide 5 mg From Glucagon-Like Peptide-1 Receptor Agonists: Clinical Expectations in the First 12 Weeks of Treatment.. Endocrine practice : official journal of the American College of Endocrinology and the American Association of Clinical Endocrinologists, 30(8), 701-709. https://doi.org/10.1016/j.eprac.2024.05.005