Mounjaro vs Retatrutide: What to Know

Retatrutide is a new medication in development from Eli Lilly — the same company that makes Mounjaro. It uses three hormones instead of two. Early Phase 3 data suggests it may produce stronger weight loss, but it is not yet FDA-approved and not available at any pharmacy.

Helpful Products for GLP-1 Treatment

Managing your GLP-1 medication is easier with the right tools:

Sharps container — Essential for safe needle disposal. A sharps container is required for home use.
Ginger products — Manage nausea with ginger chews or ginger tea.
Water bottle — Stay hydrated to reduce side effects. A large water bottle helps you track intake.
Electrolyte packets — Prevent dehydration. Liquid I.V. packets dissolve easily in water.

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Quick Comparison

	Mounjaro	Retatrutide
Active drug	Tirzepatide	Retatrutide
Drug class	Dual GIP/GLP-1 agonist	Triple GIP/GLP-1/Glucagon agonist
FDA approval	Type 2 diabetes (approved); obesity off-label	Phase 3 trials (three positive results as of May 2026)
Dosing	Once weekly	Once weekly (in trials)
Status	Available by prescription	Not available — investigational

What Is Retatrutide?

Retatrutide mimics three hormones:

GLP-1 — signals fullness, slows digestion
GIP — works with GLP-1 to boost the effect
Glucagon — increases energy expenditure (burns more calories)

Mounjaro uses the first two. Retatrutide adds the third. That extra glucagon component is what makes it a triple agonist — and what may account for the stronger weight loss results seen in trials.

Weight Loss Results: Direct Comparison Table

The table below compares Phase 3 trial results. Important caveat: these are cross-trial comparisons, not head-to-head studies. Each trial enrolled different populations, used different durations, and measured endpoints differently. Direct numerical comparison should be interpreted with caution.

	Mounjaro (SURPASS-2)	Retatrutide (TRIUMPH-1)
Mechanism	Dual agonist (GLP-1 + GIP)	Triple agonist (GLP-1 + GIP + glucagon)
Trial population	Type 2 diabetes	General obesity (no diabetes)
Trial duration	40 weeks (primary); 72 weeks extension	80 weeks (primary); 104 weeks extension
Highest dose weight loss	~22% (15 mg, T2D population)	28.3% at 80 wks (12 mg); 30.3% at 104 wks (BMI ≥35 subset)
% reaching ≥30% weight loss	Not reported	45.3% (12 mg at 80 wks)
FDA status	Approved (T2D 2022)	Not yet filed; Phase 3 ongoing
Current availability	Available by prescription	Not available — investigational

Key limitations of this comparison

SURPASS-2 enrolled people with type 2 diabetes; TRIUMPH-1 enrolled people with obesity without diabetes — different populations
Different trial durations (40 vs 80 weeks primary)
Different statistical methods and estimand frameworks
No head-to-head trial exists between these two drugs

These numbers give a general sense of relative efficacy, but no drug can be definitively ranked against another without a head-to-head trial.

Other retatrutide Phase 3 results

Retatrutide has three completed Phase 3 trials as of May 2026:

TRIUMPH-1 (general obesity): up to 28.3% weight loss at 80 weeks; 30.3% at 104 weeks in BMI ≥35 subset
TRIUMPH-4 (obesity with knee osteoarthritis): up to 28.7% weight loss at 72 weeks
TRANSCEND-T2D-1 (type 2 diabetes): up to 17.0% weight loss and 2.2% A1C reduction at 40 weeks

Side Effects

Both drugs cause similar GLP-1–related side effects. The glucagon component in retatrutide adds one potential difference.

Common to both:

Nausea
Decreased appetite
Diarrhea or constipation
Vomiting

Retatrutide-specific signals:

Increased heart rate — from the glucagon component, being monitored in trials
Dysesthesia (tingling or burning sensation) — reported in 20.9% of people at the 12 mg dose in TRIUMPH-1. Most cases were mild and did not cause people to stop the drug.

Discontinuation due to side effects

Trial	Lowest dose	Highest dose	Placebo
TRIUMPH-1 (general obesity)	3.0% (4 mg)	11.3% (12 mg)	4.9%
TRIUMPH-4 (knee OA)	12.2% (9 mg)	18.2% (12 mg)	4.0%
TRANSCEND-T2D-1 (diabetes)	2.2% (4 mg)	5.1% (12 mg)	0%

At the 4 mg dose in TRIUMPH-1, fewer people stopped treatment than on placebo. At the 12 mg dose, 11.3% stopped due to side effects — though some discontinuations were because participants felt they had lost too much weight.

Availability

Retatrutide is not yet FDA-approved. Three Phase 3 trials have reported positive results. Several more Phase 3 readouts are expected in 2026, including trials for obstructive sleep apnea, cardiovascular outcomes, and liver disease.

Here is the current timeline:

December 2025: TRIUMPH-4 results — positive
March 2026: TRANSCEND-T2D-1 results — positive
May 21, 2026: TRIUMPH-1 results — positive
June 2026: Detailed data to be presented at ADA Scientific Sessions
2026 (ongoing): Remaining Phase 3 readouts expected
Earliest likely FDA filing: Late 2026 or 2027 — Lilly has not announced a specific date
Earliest possible approval: 2027 at the soonest, assuming a timely filing

The FDA review process typically takes 6–10 months after filing. Do not make medical decisions based on an assumed approval date.

Cost

No pricing yet. It will likely be priced similarly to Mounjaro/Zepbound (~$1,060/month). Insurance coverage is unknown and will depend on the approved indication.

Who Might Benefit?

People who plateau on tirzepatide
People who want the strongest possible weight loss
People who respond well to Eli Lilly medications

But remember — retatrutide is not available yet. If you need weight management help now, Mounjaro and other approved GLP-1 medications are available and effective. Talk to your doctor about current options.

FAQ

When will retatrutide be available?

Retatrutide is not yet FDA-approved. Three Phase 3 trials (TRIUMPH-1, TRIUMPH-4, and TRANSCEND-T2D-1) have reported positive results as of May 2026, with several more Phase 3 readouts expected in 2026. The earliest likely FDA filing is late 2026 or 2027, with potential approval in 2027. Lilly has not announced a specific filing date.

Is retatrutide stronger than Mounjaro?

Phase 3 trial data suggests retatrutide may produce greater weight loss than Mounjaro. TRIUMPH-1 showed up to 28.3% weight loss at 80 weeks (with a subset reaching 30.3% at 104 weeks) vs approximately 15–22% for Mounjaro at maximum dose. However, these are cross-trial comparisons — not head-to-head — and retatrutide is not yet approved. Individual results may vary.

What is the main difference between Mounjaro and retatrutide?

Mounjaro (tirzepatide) targets two hormones — GLP-1 and GIP. Retatrutide targets three hormones — GLP-1, GIP, and glucagon. The added glucagon component may increase calorie burning, which could explain the stronger weight loss results seen in trials.

Should I switch from Mounjaro to retatrutide when it becomes available?

Talk to your doctor. If Mounjaro is working well for you, there may be no reason to switch. Retatrutide may be an option for people who do not get enough weight loss on current medications, but it will not be available until at least 2027.

What did the TRIUMPH-1 trial show?

TRIUMPH-1 is the general obesity Phase 3 trial for retatrutide. Results reported May 21, 2026 showed up to 28.3% average weight loss at the highest dose (12 mg) over 80 weeks. A subset of participants with BMI ≥35 who continued treatment to 104 weeks reached 30.3% weight loss. Retatrutide remains investigational and is not FDA-approved.

Bottom Line

Retatrutide offers stronger weight loss than Mounjaro in Phase 3 trials — up to 28.3% in general obesity (TRIUMPH-1) with a subset reaching 30.3% at 104 weeks, compared to around 15–22% for Mounjaro. It is not yet FDA-approved. With three positive Phase 3 results now in hand, the earliest possible approval is 2027.

If Mounjaro is working for you now, there is no reason to wait. If you are not getting the results you want, talk to your doctor about current options — retatrutide is not available yet and should not factor into today's treatment decisions.