Retatrutide vs Tirzepatide: Which Loses More Weight?

Retatrutide and tirzepatide are two of the most discussed peptides in the weight-research space, and the question people keep asking is simple: which one is associated with more weight loss in published trials? The short answer from the trial data is that retatrutide reported larger reductions, but there is a major catch that changes how that number should be read.

This page compares the two on reported trial outcomes, how they work, and where each stands with the FDA. It is reference information only, not advice. If you are modeling doses for either compound, the retatrutide dose calculator handles the concentration math so you are working from real numbers instead of guesses.

The headline trial numbers

The angle most people cite comes from separate phase trials, so this is a cross-trial comparison, not a head-to-head study. In a 48-week phase 2 trial of retatrutide, the highest dose group reported an average body-weight reduction of about 24.2% at 48 weeks, with modeling suggesting weight had not yet plateaued. In a 36-week extension reported at the high dose, the figure reached roughly 28.7%.

Tirzepatide's pivotal SURMOUNT-1 trial reported an average reduction of about 22.5% at the highest dose over 72 weeks. So the commonly quoted matchup is 28.7% versus 22.5%.

Why the mechanisms differ

The clearest real difference between the two is how many receptors they target. This is where the science, not the marketing, separates them.

• Tirzepatide is a dual agonist. It activates GIP and GLP-1 receptors, the two pathways tied to appetite signaling and glucose handling.
• Retatrutide is a triple agonist. It adds a third target, the glucagon receptor, on top of GIP and GLP-1. The glucagon arm is thought to influence energy expenditure and liver fat, which is the proposed reason for the larger reported reductions.

For a deeper split on the GLP-1 versus dual-agonist side, see semaglutide vs tirzepatide. For the triple-agonist comparison against another newcomer, survodutide vs retatrutide covers the glucagon angle.

The FDA-status reality check

This is the part that matters most and the part most comparisons skip. The two compounds are not in the same regulatory category.

• Tirzepatide is FDA-approved and sold as a finished prescription product under established brand names. It has completed large phase 3 trials.
• Retatrutide is investigational. As of this writing it has not received FDA approval and remains in clinical trials. It is not an approved medicine, and the long-term safety record is still being built.

So a higher trial percentage for retatrutide sits next to a much shorter and thinner safety dataset. A compound still in trials has not cleared the bar that an approved product has. That gap is a real consideration, not a footnote.

A worked concentration example

Because retatrutide is research-grade and ships as a lyophilized powder, you reconstitute it yourself, which means the dose math is on you. Say you have a 10 mg vial and add 1 mL of bacteriostatic water. That gives 10 mg/mL, or 10,000 mcg/mL.

1. Concentration: 10 mg in 1 mL = 10 mg/mL.
2. On a U-100 insulin syringe, 1 mL = 100 units, so each unit holds 0.1 mg (100 mcg).
3. A 2 mg draw would be 20 units; a 4 mg draw would be 40 units.

Change the water volume and every unit number changes with it. Run your own vial size and target through the retatrutide calculator or the general reconstitution calculator so the syringe units match your actual vial. For dose ranges seen in the literature, retatrutide dosing guide lays out the trial-tier schedule.

Which one loses more weight?

On trial numbers alone, retatrutide reported the larger reduction (about 28.7% versus 22.5%). But those numbers come from separate studies, and retatrutide is still investigational while tirzepatide is approved with a fuller safety record. The percentage is one input. Regulatory status, trial maturity, and a clinician's judgment are the rest. Dosing decisions belong with a licensed professional, and nothing here is medical advice. See the disclaimer for the full picture.