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Retatrutide vs Tirzepatide

Updated 14 sources

Key differences

  1. 1Retatrutide hits GLP-1, GIP and glucagon receptors. Tirzepatide hits GLP-1 and GIP.
  2. 2Across trials, retatrutide 12 mg gave about 24% loss at 48 weeks (phase 2) and 28.3% at 80 weeks (TRIUMPH-1). Tirzepatide 15 mg gave 20.9% at 72 weeks in SURMOUNT-1. These are cross-trial numbers.
  3. 3TRIUMPH-5 compares them head to head in about 800 adults over 80 weeks. No results yet.
  4. 4Tirzepatide climbs in 2.5 mg steps over about 20 weeks. Retatrutide reaches 12 mg in about 16 weeks on the TRIUMPH ladder.
  5. 5Skin tingling (dysesthesia) shows up on retatrutide with no matching signal on tirzepatide.
  6. 6Tirzepatide is FDA approved as Mounjaro and Zepbound. Retatrutide is not approved.
  7. 7Retatrutide adds glucagon-receptor action on top of GIP and GLP-1 (triple agonist). It is not approved anywhere; tirzepatide is FDA approved.
  8. 8TRIUMPH-1 (80 weeks): retatrutide cut weight 19.0%, 25.9% and 28.3% on 4, 9 and 12 mg vs 2.2% on placebo. SURMOUNT-1 reported 20.9% on tirzepatide 15 mg. Cross-trial numbers.
  9. 9TRIUMPH-4 reported 28.7% weight loss at 68 weeks on retatrutide 12 mg.
  10. 10Stopping for side effects in TRIUMPH-1: 4.1%, 6.9% and 11.3% vs 4.9% on placebo. Zepbound trials: 4.8%, 6.3% and 6.7% vs 3.4%.
  11. 11The head-to-head trial, TRIUMPH-5 (about 800 patients), is expected to read out in December 2026.
  12. 12No tirzepatide-to-retatrutide dose conversion exists. One guide waits 7 days after the last tirzepatide shot and starts retatrutide at 2 mg.

Side by side

Facts from each record, in the same words as their own pages.
Retatrutide and Tirzepatide side by side
RetatrutideTirzepatide
Category
  • GLP-1, Weight loss
  • GLP-1, Weight loss
Evidence
  • Strong human trials
  • Strong human trials
FDA status
  • In clinical trialsRegulatory
  • FDA approved as Mounjaro +1Regulatory
WADA
  • Not confirmed
  • Not prohibited
Half-life
  • About 6 days in the phase 1b trial, with exposure rising in proportion to dose. Built for once-weekly shots.Clinical study
  • About 5 days (Mounjaro label); 5 to 6 days in people with obesity or sleep apnea (Zepbound label). That is why it is dosed once a week.Regulatory
Routes
  • Subcutaneous injection
  • Subcutaneous injection
Reported doses
  • 0.25 to 12 mg (subcutaneous injection)
  • 0.25 to 15 mg (subcutaneous injection)
Most cited frequency
  • Once weekly. Start at 2 mg, step up every 4 weeks to a target of 4, 9 or 12 mg, then hold.
  • Once weekly. Step up 2.5 mg after at least 4 weeks only if needed, then hold the maintenance dose.
Vial sizes
  • 5 mg, 10 mg, 12 mg, 15 mg, 20 mg, 24 mg, 30 mg, 40 mg, 50 mg, 60 mgCompetitor guide
  • 10 mg, 15 mg, 20 mg, 30 mg, 40 mg, 50 mg, 60 mgVendor guide
Mixed vial keeps
  • Keep the mixed vial in the fridge and use it within about 28 days.Community-reported
  • Keep the mixed vial in the fridge and use it within about 28 days.Competitor guide
Protocols on file
  • 18
  • 12

Doses shown are what sources report, labelled by origin. Not medical advice.

Read each in full

Sources

14 sources, each checked by date. Record updated Oct 23, 2026. Numbers are restated in our own words and labelled by where they came from.

Clinical study7

  1. Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 TrialNew England Journal of Medicine · checked Oct 23, 2026
  2. Preliminary results of retatrutide from TRIUMPH-1Lilly Medical · checked Oct 23, 2026
  3. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1)New England Journal of Medicine · checked Oct 23, 2026
  4. How does retatrutide compare with other incretin-based therapies?Lilly Medical · checked Oct 23, 2026

Competitor guide3

  1. Retatrutide vs tirzepatidePeptides Explorer · checked Oct 23, 2026
  2. Retatrutide ProtocolPeptide Dosing Protocols · checked Oct 23, 2026
  3. Switching tirzepatide to retatrutidePeptideDeck · checked Oct 23, 2026