TopGLP1
Investigational (not yet FDA-approved)

Retatrutide

Triple GIP/GLP-1/glucagon receptor agonist · Subcutaneous injection · Sold as (no brand name yet)

An experimental “triple agonist” that produced the largest weight loss seen in trials so far — but it is not yet approved and not legally available.

Last reviewed 2026-09-01 by the TopGLP1 Editorial Team

Educational, not medical advice. This page explains GLP-1 medications in general terms. Only a licensed clinician who knows your history can decide what's right for you.

Key takeaways

  • Triple agonist: GIP + GLP-1 + glucagon.
  • Phase 2 trials showed ~24% average weight loss at 48 weeks — the highest so far.
  • NOT FDA-approved and NOT legally available — beware anything sold as retatrutide online.
  • Phase 3 trials are ongoing; approval, if it comes, is still in the future.

Retatrutide is an investigational once-weekly injection that hits three receptors: GIP, GLP-1 and glucagon. The added glucagon activity is thought to raise energy expenditure on top of appetite suppression.

In a phase 2 trial, participants on the highest dose lost an average of around 24% of body weight at 48 weeks — the highest figure reported for any drug in this class — which is why it has generated so much attention.

Crucially, retatrutide is still in clinical trials and has not been approved by the FDA. It cannot be legally prescribed or compounded, and any product sold online claiming to be retatrutide is unregulated and potentially dangerous.

How retatrutide works

Retatrutide builds on the dual-agonist idea by adding a third target: the glucagon receptor. GLP-1 and GIP reduce appetite and improve blood sugar; glucagon activation is believed to increase the body's energy use and support fat metabolism.

In theory, pairing appetite suppression with higher energy expenditure could push weight loss beyond what dual agonists achieve — and early data are consistent with that. But the full safety picture only emerges from larger, longer phase 3 studies.

How well it works

~24% average weight loss at 48 weeks in phase 2 (highest dose).

A phase 2 study reported dose-dependent weight loss, reaching roughly 24% on average at the top dose at 48 weeks, with a meaningful share of participants losing more than 30%. These are early results and not a substitute for phase 3 confirmation.

Phase 2 (obesity)~17%–24% mean weight loss across doses at 48 weeks
Phase 3 programOngoing — results and any approval decision are still pending

Dosing schedule

There is no approved dosing schedule because retatrutide is not approved. Trial protocols use slow escalation similar to other GLP-1-class drugs, but this information is for education only.

Trials onlyEscalating weekly doses under study

No approved or legal dosing exists for the public.

  • Do not attempt to source or self-administer retatrutide — no legitimate, quality-controlled supply exists outside clinical trials.

Side effects & safety

Common

  • • Nausea
  • • Diarrhea
  • • Vomiting
  • • Constipation
  • • Increased heart rate reported in trials at higher doses

Serious (uncommon)

  • • Full long-term safety is unknown pending phase 3 data
  • • Glucagon activity requires careful study of effects on blood sugar and heart rate

Because retatrutide is investigational, its complete side-effect and safety profile has not been established. This is one of the main reasons approval takes years.

What it costs

Branded (cash)
Not available for purchase — no legal market exists
Insurance
Not applicable. If approved in the future, pricing and coverage would be set at that time.

Who it's for — and who should avoid it

Often a good fit

  • People following GLP-1 research who want to understand what may come next
  • Potential clinical-trial participants (through legitimate, registered studies only)

Not recommended for

  • Anyone looking to buy or use it now — it is not legally or safely available

Common questions

No. It is investigational and not FDA-approved. Any website selling “retatrutide” for personal use is operating outside the law and outside quality controls, which is genuinely dangerous. The only legitimate access is through an enrolled clinical trial.

How retatrutide compares

Tirzepatide vs Retatrutide

Sources & references

Clinical figures on this page trace to peer-reviewed trials and official regulators. We link the primary record so you can verify it yourself.

  1. 1.
  2. 2.

Keep reading

Basics

How GLP-1 Medications Actually Work