Retatrutide vs Tirzepatide vs Semaglutide: Which GLP-1 Is Right For You?

Retatrutide vs tirzepatide comes down to receptors and trial numbers. Tirzepatide is a two-receptor (GLP-1 + GIP) compound, FDA approved, with around 21-23% body-weight loss reported in trials. Retatrutide adds a third receptor (glucagon) and reached roughly 28-30% in Phase 3 topline, the higher-potency option but the newest, with the least long-term safety data.

Fat loss comes down to one thing at the core: energy in versus energy out. Take in more energy (calories) than you burn and the surplus is stored as fat; burn more than you take in and your body dips into the stores. It is basic thermodynamics, and nothing escapes it, not a peptide, not a drug. GLP-1s act on the "energy in" side by reducing appetite. All three compounds below are GLP-1 drugs, and that is the frame for telling them apart.

Three compounds dominate the weight-loss conversation right now, and people throw the names around as if they were the same drug. They are not. Semaglutide (sold as Ozempic and Wegovy) kicked the whole thing off. Tirzepatide (Mounjaro and Zepbound) pushed the trial results further. And retatrutide, still going by its lab name because it has not been branded yet, is the new arrival posting the biggest trial numbers of the lot.

The difference between them is simpler than it sounds. Each one acts on one, two, or three metabolic receptors, and as a rule, more receptors has tracked with more weight loss in trials and more to keep an eye on.

A quick word on where we stand: Primogen carries retatrutide and tirzepatide, and not semaglutide. The reasoning is below. All three are sold as research compounds, and this guide is about separating what is genuinely proven from what is still playing out.

Retatrutide vs tirzepatide vs semaglutide: how do they compare at a glance?

In one line: semaglutide is the single-receptor original (~15% in trials), tirzepatide the dual-receptor middle ground (~16-22.5%), and retatrutide the triple-receptor newcomer (~24% Phase 2, up to ~30% Phase 3 topline). The full side-by-side is below.

How do the three compounds differ in how they work?

They differ by how many receptors each one activates: semaglutide hits one (GLP-1), tirzepatide two (GLP-1 + GIP), and retatrutide three (GLP-1 + GIP + glucagon). All three are designed to mimic the gut hormones the body releases after a meal, and the receptor count is the main mechanistic distinction between them.

Semaglutide is a pure GLP-1 agonist, a molecule that activates a receptor, the receptor being the cell's docking point for GLP-1, one of the gut hormones released after a meal. In published pharmacology it acts on hunger-signalling neurons in the brain, slows gastric emptying, and improves glycaemic control (Coskun et al. 2022 describes the multi-receptor pharmacology of this class). That single mechanism is the basis of Ozempic and Wegovy.

Tirzepatide adds GIP, a second gut hormone that acts alongside GLP-1. In the research literature GIP co-agonism is associated with improved insulin sensitivity and, in trials, greater weight loss than semaglutide with a comparable gastrointestinal side-effect profile. That trial separation is how tirzepatide, as Mounjaro and Zepbound, became the dual-agonist benchmark.

Retatrutide adds a third receptor, glucagon, a metabolic hormone that mobilises stored energy, and that is what changes the character of the molecule. In animal and early-phase pharmacology, glucagon agonism is associated with increased resting energy expenditure, direct lipolysis, and reduced liver fat (Coskun et al. 2022). That added mechanism is why retatrutide posts the highest total weight-loss figures of the three in trials, and it underpins the wider metabolic findings further down.

In short: semaglutide and tirzepatide act mainly on appetite pathways. Retatrutide's triple-agonist design also targets resting energy expenditure.

Worth being straight about one thing, though: milligram for milligram, retatrutide's appetite-suppression signal in trials is a touch weaker than tirzepatide's, and it can taper a little faster. Its trial edge does not come from stronger appetite effects. It comes from acting on fat through more mechanisms at once.

What does the trial data show on weight loss?

In the registration trials, average body-weight loss climbs with each added receptor: roughly -15% for semaglutide, up to -22.5% for tirzepatide, and up to -24.2% (Phase 2) to ~30% (Phase 3 topline) for retatrutide. Here is the breakdown for the trials that got each compound over the line, or for retatrutide the trials still running:

• Semaglutide (STEP program): roughly -15% average body-weight loss at the 2.4 mg weekly dose.
• Tirzepatide (SURMOUNT-1): -16.0% / -21.4% / -22.5% at 72 weeks for the 5 / 10 / 15 mg doses.
• Retatrutide (Phase 2, Jastreboff et al. 2023, NEJM): up to -24.2% at 48 weeks on 12 mg, and the loss curve had not flattened by the end of the study. Phase 3 TRIUMPH-1 topline (reported May 2026): up to 30.3% average weight loss on the highest dose, the strongest non-surgical weight-loss figure reported to date.

Two things to keep honest here. That reta Phase 3 number is topline data straight from Lilly, not a full peer-reviewed paper yet, so take it as very promising rather than carved in stone. And trial figures come from supervised dosing with proper titration (raising the dose gradually in steps) and clinical support, so reported real-world figures are usually lower.

What sets retatrutide apart from the other two?

What sets it apart is the breadth of metabolic findings in its trials, not just the weight-loss number. Beyond the scale, retatrutide's Phase 2 data, most of it peer-reviewed, reports changes across several metabolic markers:

• Liver fat: in one Phase 2 study, around an 82% reduction in liver fat was reported (Sanyal et al. 2024, Nature Medicine), attributed to the glucagon axis.
• Lipids: the same Phase 2 dataset reported drops in triglycerides (~40%) and LDL cholesterol (~22%) at 48 weeks on 12 mg (Healio / ADA 2023 coverage).
• Blood sugar: the type 2 diabetes Phase 2 trial reported improved glycaemic control (Rosenstock et al. 2023, Lancet).
• Metabolic rate: in its pharmacology, the glucagon component is associated with raised resting energy expenditure, rather than relying on appetite pathways alone.

And Lilly is not hedging. The TRIUMPH program runs from TRIUMPH-1 through TRIUMPH-8, plus a dedicated cardiovascular outcomes trial, covering obesity, diabetes and long-term health. That is the same road semaglutide and tirzepatide walked before they became household names. Approval is widely expected, and when it lands, retatrutide will almost certainly pick up a brand name of its own. Until then, it sits in the research-compound window under its original name.

The flip side, said plainly: retatrutide is the newest of the three, so it has the least long-term safety data behind it. Its cardiovascular outcomes will not be in until the TRIUMPH-Outcomes trial wraps up, around 2030.

Why does Primogen not stock semaglutide?

Because the trial data moved past it: tirzepatide and retatrutide both report greater weight loss, so Primogen carries those two rather than the most famous name out of habit. Semaglutide was the breakthrough that started all of this, and if it is specifically what you are after, that is a perfectly reasonable call. It is just not part of the range here.

Is weight regained after stopping a GLP-1?

In the withdrawal trials, yes: a large share of lost weight returned within a year of stopping. The mechanism, as described in the literature, is that these compounds act by suppressing appetite, so when they clear the system the appetite and food noise signals return, and weight loss itself lowers metabolic rate while the body defends its prior set-point. In the STEP 1 extension, participants regained roughly two-thirds of lost weight in the year after stopping semaglutide (Wilding et al. 2022, STEP 1 extension). In SURMOUNT-4, 82% regained at least a quarter of what they had lost after tirzepatide was withdrawn (Aronne et al. 2023, JAMA). No published withdrawal data exists yet for retatrutide. The takeaway researchers draw is to treat these as long-term tools and to use the dosing window to build training and nutrition habits that help hold a result in place.

What side effects do these compounds have in the trials?

The reported side effects are broadly similar across all three and mostly gastrointestinal: nausea, vomiting, diarrhoea, constipation. In the trials they track with dose, are most pronounced during titration, and tend to ease over time.

• Nausea is the most-discussed. In retatrutide trials it was reported from about 14% at low doses up to about 45% at 12 mg, a similar shape to the other two.
• Heart rate rose across this class in the trials, most so for retatrutide, by roughly 6-11 bpm. A consideration for anyone with a baseline cardiac concern or stimulant use.
• Dysesthesia (odd skin sensations, tingling or hypersensitivity) is a newer signal specific to retatrutide, reported in up to around 21% at 12 mg in Phase 3. Rarely a reason participants stopped, but documented.
• Rare but serious: pancreatitis and gallbladder events are class-wide risks reported for all three.

One signal that catches researchers' attention is lean-mass loss. When appetite falls sharply, protein intake can drop and lean mass can be lost alongside fat. The literature's standard mitigation is resistance training and adequate protein, the most-cited lever for preserving lean mass during weight loss.

How are these compounds typically dosed in research?

Both are weekly compounds in the trial protocols, started at a low dose and titrated up over several weeks, with the slow climb being the key variable for tolerability. The trial titration schedules are:

• Tirzepatide: 2.5 mg weekly to start, titrating toward 5-15 mg.
• Retatrutide: low starting doses titrating up; in the literature most weight-loss protocols sit at or below the 12 mg tested in trials, with research handling typically staying in the lower 3-4 mg range.

A worked reconstitution example (handling, not a dosing instruction). Take a 10 mg vial of tirzepatide reconstituted with 1 mL (1000 units) of bacteriostatic water. That gives a concentration of 10 mg / 100 units, so 1 unit on a U-100 insulin syringe holds 0.1 mg. A 2.5 mg measure is therefore 25 units drawn to the syringe's 25-unit mark; a 5 mg measure is 50 units. If the same 10 mg vial is reconstituted with 2 mL instead, the concentration halves to 0.05 mg/unit, so a 2.5 mg measure becomes 50 units. Same vial, different water volume, different mark on the barrel, which is exactly why the reconstitution volume has to be written down rather than guessed.

Some researchers also microdose these (small, sub-clinical weekly amounts) when the interest is metabolic and longevity markers rather than maximum weight loss, trading effect size for fewer reported side effects. The retatrutide deep-dive and tirzepatide deep-dive lay out the full protocols, and how to reconstitute and dose covers the maths in detail.

How much do retatrutide and tirzepatide cost, and how do you assess quality?

Both sit at the premium end, with retatrutide a little pricier as the newer compound; the live pricing is in the table below. One honest aside on quality, since the industry tends to stay quiet about it: research peptides mostly come out of China, and proper per-batch third-party testing is thin on the ground across the whole sector. Read the certificate of analysis on whatever you buy, and know what it does and does not actually prove. There is a plain-English walkthrough in how to read a COA.

Produk terkait

Retatrutide

mulai dari Rp 2.550.000

Tirzepatide

Rp 1.990.000 · 30mg

Which one should you choose: retatrutide or tirzepatide?

The verdict: retatrutide if you want the highest-potency option and are comfortable with the newest safety file; tirzepatide if you want the FDA-approved compound with the longest track record. Semaglutide is outpaced by both on trial weight loss and is not stocked here. Here is the buyer mapping.

Who should choose retatrutide. The reader who wants the strongest trial weight-loss figures and the broadest metabolic data (liver fat, lipids, glycaemic markers), who does not feel the need to "earn it" by starting milder, and who is fine being on the newest of the three while its long-term record is still being written.

• Not a fit if you specifically want an already-approved compound, want the longest cardiovascular safety record (its outcomes trial does not report until around 2030), or are sensitive to a higher heart-rate signal.

Who should choose tirzepatide. The reader who wants the FDA-approved option with the most mature safety history, the gentlest heart-rate effect, the strongest milligram-for-milligram appetite-suppression signal in trials, or the friendlier price. It is the dual-agonist benchmark for good reason, and that is why it stays on the shelf here.

• Not a fit if your priority is the single highest weight-loss figure on record or the widest metabolic dataset; on those measures the trial data favours retatrutide.

Who would have chosen semaglutide. The reader who wants the single most-studied, lowest-cost name.

• Not a fit if you want the best trial weight-loss outcome, since both stocked compounds outperform it in the data, which is why Primogen does not carry it.