Retatrutide research: studies, doses and safety

• Weeks 1-8: TRIUMPH-1 started at 2 mg weekly for four weeks, then 4 mg weekly, with dose reductions allowed for stomach problems.
• Weeks 9-12, higher-dose groups: The trial moved higher-dose groups to 6 mg weekly while the 4 mg group stayed at its target.
• Weeks 13-16, higher-dose groups: The trial moved higher-dose groups to 9 mg weekly while the 4 mg group stayed at its target.
• Week 17 onward, highest-dose group: The highest-dose group reached 12 mg weekly after 16 weeks of dose increases.
• Week 80: TRIUMPH-1 reported average weight loss of 17.6-25.0% across target doses versus 3.9% with placebo, with stomach side effects most common.

TRIUMPH-1 studied weekly injections for 80 weeks in adults with obesity without diabetes.

40 primary human records: 34 registered studies, including one exercise study, four case or observational reports, and two social-media studies. The 40 include ongoing studies and studies without results.

Key studies

• First-in-human single-dose study (Coskun 2022): The single-dose study found a long half-life. It did not test repeated microdosing. (source)
• Phase 1b multiple-dose diabetes trial (Urva 2022): Weekly doses improved glucose and weight in a small early trial. (source)
• Phase 2 obesity trial (Jastreboff 2023): Average weight loss increased with dose, reaching 24.2% at 48 weeks in the 12 mg arm. (source)
• Phase 2 diabetes trial (Rosenstock 2023): The 8 and 12 mg groups had larger blood sugar and weight reductions, with more stomach upset. (source)
• TRIUMPH-1 phase 3 obesity trial (Jastreboff 2026): Published phase 3 results showed weight loss and improvements in knee pain and sleep-apnea measures. (source)
• TRANSCEND-T2D-1 phase 3 diabetes trial (Bajaj 2026): Retatrutide lowered glucose and weight over 40 weeks without background diabetes medicine. (source)