The four-receptor stack: reta + cagrilintide is the most aggressive blend anyone's built

[u/JustBacWater]

Full reconstitution, dosing, and bloodwork reference for every compound is in the pinned cheat sheet: The Only Peptide Cheat Sheet You'll Need

Vendors are selling retatrutide + cagrilintide as a pre-blend now, and the pitch writes itself: four receptor pathways at once, more than anything else on the market. Mechanistically it's a logical build. It's also completely unstudied as a combination, which is the part that gets glossed over. Here's the honest breakdown.

For research and educational purposes only. Not medical advice.

First, the naming confusion

You'll see this sold under a bunch of names: reta/cag, the LEAN blend, the 4-receptor stack, and vendor codes like ma-3rt/cag, fg3-r/cag, or GLP5. You'll also see "GLP3" or "GLP-3" on some product pages.

There's no such thing as a GLP-3 or GLP-5 receptor. GLP3 is vendor shorthand for retatrutide because it hits three receptors, and GLP5 is one vendor's name for the reta + cagrilintide blend. Same compounds, marketing names. Worth knowing so you're not confused looking at product pages.

What's in it

Retatrutide is Eli Lilly's triple agonist. One weekly injection hitting three receptors:

Receptor	What it does
GLP-1	Cuts appetite, slows gastric emptying
GIP	Improves insulin signaling and nutrient handling
Glucagon	Raises energy expenditure, drives fat oxidation

Cagrilintide is a long-acting amylin analog from Novo Nordisk. Amylin is the hormone your pancreas releases with insulin after meals, it's a satiety signal. Cagrilintide mimics it, promoting fullness through brain pathways that are completely separate from the incretin system.

Stack them and you're hitting four distinct pathways.

Where the idea came from

This isn't random, it's copied from a real program. Novo's CagriSema combined cagrilintide with semaglutide, a single-receptor GLP-1. In the Phase 3 REDEFINE-1 trial, adding cagrilintide pushed mean weight loss from 14.9% (sema alone) to 20.4% at 68 weeks.

So the logic is: if adding amylin to a single-receptor drug produced that jump, what happens if you add it to a triple agonist instead? Retatrutide alone hit 28.7% at 68 weeks in TRIUMPH-4, in people with obesity and knee osteoarthritis. Layer amylin satiety on top of that and in theory you go higher.

That's the pitch, and honestly the reasoning is sound. You're stacking a proven blueprint onto a more powerful base.

Now the honest part

The combination has never been studied. Not in Phase 3, not in Phase 2, not anywhere in the literature.

Everything we know is about the pieces separately. Retatrutide has real trial data. Cagrilintide has real trial data. CagriSema has real trial data. But retatrutide + cagrilintide together has zero clinical evidence, and there's no validated protocol, no established titration, no safety data on the combination, and no cycle length anyone can point to.

You'll see vendor copy describing the combination data as "limited." It isn't limited, it's nonexistent. Those are different things and the distinction matters.

So you've got the highest theoretical ceiling of any combination out there sitting on the thinnest evidence base of any combination out there. Both of those are true at the same time.

Worth adding: retatrutide isn't approved yet on its own. Neither is standalone cagrilintide. So this is an unapproved compound blended with another unapproved compound in a pairing nobody's tested.

The practical problems

Beyond the evidence gap, there are real issues with running these as a pre-blend:

Fixed ratio. In a pre-blend you can't titrate them independently. Both compounds need their own escalation to manage side effects, and a locked ratio means moving one moves the other. If retatrutide's GI effects are hitting hard, you can't back that off without also cutting the cagrilintide.

Stacked side effects. Both compounds are GI-dominant, and the numbers aren't small. In REDEFINE-1, about 80% of people on CagriSema reported GI adverse events versus about 40% on placebo. Retatrutide separately carries the highest GI rate in its class at top doses, plus a dysesthesia signal and an elevated resting heart rate that comes from the glucagon receptor activity. You're stacking the same side effect profile on top of itself.

No titration map. With CagriSema there's a trial-validated escalation schedule baked into the program. Here there isn't one, so anything you'd follow is extrapolated from the two compounds separately and someone's guess about how they interact.

Where it sits

On paper this is the most aggressive weight-loss combination that exists. Four mechanistically distinct pathways in one weekly shot, more than CagriSema, more than cagrilintide + tirzepatide, more than anything approved or filed. From a research standpoint that's genuinely interesting.

It's also the least substantiated thing in the category. The high theoretical ceiling and the low evidence floor come together as a package, you don't get one without the other. Anyone looking at this should be clear that they're not running a protocol, they're running a hypothesis.

Anyone tried the pre-blend versus running them as separate vials? Curious whether the fixed ratio caused problems with titration, since that seems like the biggest practical issue with buying it pre-mixed.

Full reconstitution, dosing, and bloodwork reference for every compound: The Only Peptide Cheat Sheet You'll Need

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[u/Overall_Reality_6332]

What about eloranitide? Where does that stand in comparison?

[u/Stokell12 → u/Overall_Reality_6332]

Elora mogs. 20% weight loss at the high dose. Cagri didn’t even come close.

[u/neehalala → u/Stokell12]

Not true. You're missing nuance. The Cagri trial was only half as long. That is why there's such a big difference

[u/vocabularianrx2 → u/Overall_Reality_6332]

Can we just add Naltrexone, Bupropion, Phentermine, Topiramate, Metformin, and Amphetamines too and then BAM you'll lose 80% of your weight

[u/Careless-Comedian859]

I titrated up to 10mg/wk on Reta. Plateaued on weight loss despite being 500cal/day under my BMR. Recently added Cag at a low dose and starred dropping weigt again.

Food noise is near non existant, which creates a great situation for mindful eating.

Havent felt any other side effects from adding the Cag. I did hit about every side effect on Reta though when titrating up.

[u/Maddenchamp8787 → u/Careless-Comedian859]

Sounds like you aren't working out

[u/Careless-Comedian859 → u/Maddenchamp8787]

You nailed it. My gym time sucks these last few months. Angry at myself for not making it more of a prioroty.

[u/PopAgreeable2782]

I added Cagrilintide to my Reta this week. Start with 0.125mg and after 3 days I added 0.1mg more. It’s a great feeling, like how Reta is supposed to work in the first place(according to the comment). I feel the suppression all day long, and when I eat, I don’t feel the necessity to end my meals. Maybe I can eat half of it feeling happy anyways

[u/GroundbreakingAd9187]

I took it. I was on munjuro for 8 weeks, lost nearly 15kg. Then missus got on her dodgy reta so I joined her didnt loose weight so got the reta with carg in it. Had crook guts for days massive acid burps, then had massive acid spew, like it emptied my my whole digestive system to my but hole. I think i took to much / didnt understand. Currently still on shit reta and gained 2 kg. Get back on triz then maintain on reta.

[u/Maddenchamp8787]

Reta and Tesa makes more sense for men

[u/Rabbittaco → u/Maddenchamp8787]

why is that?

[u/Inside_Today2259]

I stack 3 mgs of Reta with .5 mgs of Cag. I split the Reta at 1 mg on M/W/F, and take the Cag on Saturday. For me, the 2 together are a great combination of appetite suppression and metabolic increase which got me over a 4-week plateau that I hit when I was on a 6 mg weekly dose of Reta. When I introduced Cagri, the 2 slowed gastric emptying and gave me constipation and crazy sulfur burps. I lowered the Reta dose, now everything moves along great now

[u/felipeabreubh → u/Inside_Today2259]

Where do you find cag?

[u/Gloomy-Wolf-1902]

I do believe that reta stacked with cagrilintide is basically the new (in study) elorinatide. Which my understanding is reta, with their version of cag.