GLP-1 peptides ranked: semaglutide vs tirzepatide vs retatrutide

When people talk about "GLP-1 drugs" they are actually talking about three different things at this point. Semaglutide, tirzepatide, and retatrutide all work through the GLP-1 receptor, but they are not the same compound, and the differences matter a lot if you are trying to understand what the science actually shows.

Let me walk through each one, what it does, and what the trials found. Then I will put them side by side so you can see how the numbers compare.

Semaglutide: the original

Semaglutide is a GLP-1 receptor agonist, one receptor, one pathway. It mimics GLP-1, the hormone your gut releases after you eat, which tells your pancreas to release insulin, tells your stomach to slow down, and tells your brain you are full.

The key thing that makes semaglutide work as a once-weekly drug: it was engineered to resist the enzyme that destroys natural GLP-1 in about two minutes. A fatty-acid modification lets it bind to albumin in the blood, extending its half-life to about a week.

The landmark trial for weight management: STEP 1 (Wilding et al., NEJM 2021). 1,961 adults with obesity. Mean weight loss of 14.9% at 68 weeks vs 2.4% for placebo. That was groundbreaking at the time.

Then SELECT happened. 17,604 adults with established cardiovascular disease, no diabetes. Semaglutide reduced cardiovascular death, non-fatal heart attack, and non-fatal stroke by 20% over about 40 months. That expanded the story from weight loss to CV risk reduction, which is why Wegovy got the expanded approval in 2024.

Oral semaglutide: the pill that changed the conversation

Semaglutide was injectable-only until December 22, 2025, when the FDA approved an oral tablet form (Wegovy pill) for chronic weight management. It is the same molecule, a 31-amino-acid GLP-1 peptide, reformulated for oral delivery using an absorption enhancer (SNAC) that gets it through the stomach lining intact.

The pivotal trial: OASIS 4 (Wharton et al., New England Journal of Medicine 2025;393(11):1077-1087). 307 adults without diabetes, 64 weeks. Weight loss of -13.6% versus about -2% on placebo. 76% of participants reached at least 5% weight loss, versus 31% on placebo.

That -13.6% is the treatment-policy estimand, what actually happened to the people in the trial, adherence and all. A hypothetical full-adherence model produced -16.6%, but that assumes everyone stayed on the drug at full strength, which they did not. We publish the real-world number.

The pill also carries a major adverse cardiovascular events (MACE) risk-reduction indication, reducing the risk of cardiovascular death, heart attack, or stroke in adults with overweight or obesity and established cardiovascular disease. That is a regulatory distinction it holds over orforglipron, the other oral GLP-1.

The trade-off is administration. Oral semaglutide must be taken on an empty stomach in the morning, with no more than 4 oz of plain water, then you wait at least 30 minutes before food, other drinks, or other oral medicines. Miss that window and absorption drops sharply. This is not a minor inconvenience, it is the reason an oral GLP-1 without food or water restrictions (orforglipron, approved April 2026) became commercially interesting.

Tolerability: nausea was reported by 46.6% of participants versus 18.6% on placebo. Vomiting 30.9% versus 5.9%. Discontinuation due to adverse events was 6.9% versus 5.9% on placebo, nearly identical.

There is also an older oral form: Rybelsus (oral semaglutide for type 2 diabetes), approved in 2019. It uses the same SNAC absorption technology but at lower strengths and for a different indication. Rybelsus is not approved for weight management, that is the Wegovy pill's role.

The key distinction: oral semaglutide is a peptide. Orforglipron, the other oral GLP-1, is a non-peptide small molecule. Same receptor, different chemistry, different administration requirements, different efficacy. They are not interchangeable, and they should not be conflated with the injectable.

Tirzepatide: two receptors

Tirzepatide adds GIP receptor agonism to GLP-1. GIP is another incretin, released from the small intestine, it enhances insulin secretion and plays a role in fat storage and energy balance. Activating both GIP and GLP-1 simultaneously produces a synergistic effect that goes beyond what either pathway does alone.

The key trial: SURMOUNT-1 (Jastreboff et al., NEJM 2022). 2,539 adults with obesity. Mean weight loss of 22.5% at the highest dose at 72 weeks. That was a step-change from semaglutide's ~15%.

In head-to-head vs semaglutide (SURPASS-2), tirzepatide at comparable doses produced greater HbA1c reduction and weight loss. The dual receptor approach demonstrably outperformed single-receptor agonism.

Retatrutide: three receptors

Retatrutide adds glucagon receptor agonism to the GIP + GLP-1 combination. Here is why that matters: glucagon receptor activation directly increases energy expenditure and stimulates fat breakdown (lipolysis). It is a metabolic accelerator on top of the satiety and insulin effects of the first two pathways.

The theoretical concern with activating glucagon is that glucagon raises blood glucose. Retatrutide's designers solved this by balancing the glucagon activity against the enhanced insulin secretion from GIP and GLP-1, the net effect is more fat burned without a glucose spike.

Phase 2 (NEJM 2023): 24.2% weight loss at 48 weeks at the highest dose. Phase 3 TRIUMPH-1 (80 weeks): 28.3% mean weight loss. 45.3% of participants achieved 30% or more weight loss. Approaching bariatric surgery outcomes.

Retatrutide is not FDA-approved yet. Eli Lilly plans to file a BLA in Q1 2027.

The comparison, side by side

These numbers come from different trials with different designs, durations, estimands, and sample sizes. They cannot be directly compared by subtraction. STEP 1 used a treatment-regimen estimand; OASIS 4 used a treatment-policy estimand; ATTAIN-1 used an efficacy estimand; SURMOUNT-1 used a treatment-regimen estimand. A 1.2-point gap between two of these numbers is not a clinical conclusion, it is an artifact of methodology. The table shows scope, not a ranking.

Oral vs. injectable GLP-1: what actually differs

Two oral GLP-1s are now FDA-approved: oral semaglutide (Wegovy pill, December 2025) and orforglipron (Foundayo, April 2026). Both are daily tablets. Both target the GLP-1 receptor. Beyond that, they differ in ways that matter to anyone comparing them.

Chemistry. Oral semaglutide is a peptide, the same 31-amino-acid molecule as the injection, delivered orally via an absorption enhancer. Orforglipron is a non-peptide small molecule. Same receptor target, fundamentally different drug chemistry.

Administration. This is the biggest practical difference between the two pills. Oral semaglutide requires an empty stomach, morning dosing, no more than 4 oz of plain water, and a 30-minute wait before food or other drinks. Orforglipron has no food or water restrictions, any time of day, with or without food.

Efficacy. Oral semaglutide: -13.6% weight loss (OASIS 4, treatment-policy estimand, 64 weeks). Orforglipron: -12.4% (ATTAIN-1, efficacy estimand, 72 weeks). These numbers are from different trials with different designs and cannot be directly compared. What can be said: both oral options deliver less weight loss than injectable tirzepatide (-22.5%, SURMOUNT-1) or injectable semaglutide (-13.7%, SURMOUNT-5), but they offer a route for people who will not inject.

Tolerability. Oral semaglutide: nausea 46.6%, vomiting 30.9%, discontinuation 6.9%. Orforglipron: roughly a third reported nausea, discontinuation 10.3% at the highest dose studied. Again, different trials, but the pattern is real: the pill form of semaglutide has more GI upset than the small molecule, and the small molecule has a higher discontinuation rate.

Cardiovascular indication. Oral semaglutide carries a MACE risk-reduction indication (cardiovascular death, heart attack, stroke in adults with established CVD). Orforglipron does not. If cardiovascular risk reduction is part of the conversation, this is a genuine regulatory distinction.

The honest summary. Neither oral matches the best injectable on weight loss. Both are real options for people who will not or cannot inject. The choice between the two pills comes down to administration constraints (strict versus none), tolerability profiles, and whether the cardiovascular indication matters. That is a conversation for a prescribing doctor, not a website.

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