GLP-1 receptor agonists mimic the gut hormone glucagon-like peptide-1 to improve glycemic control and drive weight loss. This hub pulls together our complete research coverage of semaglutide, tirzepatide, retatrutide and the broader incretin class — mechanism, Phase 3 data, side-effect profiles, dosing math and head-to-head comparisons.
A pharmacology-first comparison of theoretical oral tirzepatide and the subcutaneous injection. We use Rybelsus (oral semaglutide) and Wegovy as the closest real-world case study for what oral vs injection actually looks like.
There is no FDA-approved oral tirzepatide as of 2026. We review the pharmacology, the pipeline, and why Lilly chose a small-molecule GLP-1 (orforglipron) rather than an oral peptide version of tirzepatide.
Tirzepatide has a half-life of about 5 days, which means time-of-day has almost no pharmacological effect on plasma level. What actually matters is tolerability, meal timing, sleep, and picking a consistent day you will not forget.
During the 2022–2024 FDA tirzepatide shortage, compounded tirzepatide filled a real access gap at a fraction of Zepbound's list price. The shortage ended in October 2024, and the 2026 regulatory landscape looks very different. Here is the honest comparison on formulation, legality, cost, and quality.
Insomnia is not a labelled common adverse event for Zepbound in SURMOUNT-1 — but post-market FAERS reports and patient communities describe it often. Here is what the trial data actually says, the plausible mechanisms, and the mitigation strategies with the strongest evidence.
A research-grade reconstitution chart for lyophilised tirzepatide vials — vial sizes from 5 mg to 60 mg, BAC water volumes from 1 mL to 3 mL, and the insulin-syringe unit marks that correspond to common SURMOUNT doses. Includes the two math errors that waste the most peptide.
Roughly 15% of SURMOUNT-1 participants lost less than 5% body weight after 72 weeks of tirzepatide — non-response is real. These are the eight most common research-backed reasons the scale will not budge, and what to audit before increasing the dose.
Abdomen, upper thigh, or upper arm — the label-approved tirzepatide injection sites and how they actually compare on absorption, comfort, and lipohypertrophy risk. Includes a 12-week rotation chart.
A reference chart for microdosing tirzepatide — sub-therapeutic weekly doses below the SURMOUNT-1 starting point. Includes reconstitution math, syringe-unit measurements, and a 20-week comparison against the standard titration schedule.
Mazdutide, a GLP-1/glucagon dual agonist approved in China in 2025, versus retatrutide, Lilly's GLP-1/GIP/glucagon triple agonist. A side-by-side look at mechanism, trial data, approval status, and population-specific nuances.
Should you actually switch from tirzepatide to retatrutide? A plateau-aware decision framework covering trial data, FDA status, access channels, cost, and side-effect profile — not a how-to protocol.
Alopecia was reported in the Phase 2 retatrutide trial — more often at 8 mg and 12 mg than placebo. Here is what the data actually shows, the telogen effluvium mechanism behind it, and how it compares to semaglutide, tirzepatide, and bariatric surgery.
A head-to-head research comparison of Ozempic (semaglutide) and retatrutide as of early 2026. Covers mechanism, trial-published weight loss, approval status, cost, and the open questions a direct trial has not yet answered.
A step-by-step research walkthrough for reconstituting a lyophilised retatrutide vial with bacteriostatic water. Covers equipment, technique, stability window, labelling, and the most common mistakes.
A research-only walkthrough of the reconstitution math for a 10 mg retatrutide vial. Shows how 1, 2, and 3 mL of bacteriostatic water translate into insulin-syringe units at common research doses, with tradeoffs for each dilution.
A plain-English look at how retatrutide was dosed in the Phase 2 obesity trial and how TRIUMPH-1 titrates to 6 mg or 12 mg maintenance. Includes a week-by-week titration table and a dose-response table from the published NEJM data.
A research-focused review of retatrutide side effects pulled from the NEJM Phase 2 obesity trial and early TRIUMPH Phase 3 readouts. Covers GI tolerability, cardiovascular signals, discontinuation rates, and how the triple agonist stacks up against semaglutide and tirzepatide.
For most of the GLP-1 era, Medicare has not covered weight-loss drugs for obesity alone. That has changed in pieces — through cardiovascular indications, through policy proposals, and through Medicare drug-price negotiation. Here is what Medicare beneficiaries can and cannot access in 2026.
Most dual agonists in late-stage obesity trials pair GLP-1 with GIP. Survodutide takes a different route — GLP-1 plus glucagon receptor activation. The dual mechanism produced ~19% weight loss and strong liver-fibrosis improvements in Phase 2. Here is why glucagon agonism matters.
Viking Therapeutics is a mid-cap biotech trying to carve a slice out of a market dominated by Lilly and Novo. Their lead asset VK2735 is a GLP-1/GIP dual agonist in two formulations — weekly injectable and daily oral tablet — with Phase 2 data that caught the market's attention.
Weekly injections may not be the final form of GLP-1 therapy. Amgen's MariTide is a monoclonal-antibody conjugate dosed once a month — not once a week — and the Phase 2 data suggest the magnitude of weight loss holds up. Here is how the molecule works and why monthly dosing matters.
In 2026, Novo Nordisk's Phase 3 EVOKE and EVOKE+ trials tested whether oral semaglutide could slow Alzheimer's disease. The headline result was a clean miss on the primary endpoint. The biomarker results told a more complicated story — one that may change how future GLP-1-plus-anti-amyloid combination trials are designed.
For years, cross-trial comparisons told us tirzepatide outperformed semaglutide for weight loss. SURMOUNT-5 is the first randomised head-to-head trial that proved it directly. 20.2% versus 13.7% at 72 weeks — and the implications reach much further than one trial.
Novo Nordisk's CagriSema combines two peptides — cagrilintide (amylin analogue) and semaglutide (GLP-1) — in a single weekly injection. REDEFINE-1 produced 22.7% body weight loss at 68 weeks, falling short of the 25% target but putting Novo back in the race against Eli Lilly's tirzepatide and retatrutide. Here's the full data.
On April 30, 2026 the FDA proposed excluding semaglutide, tirzepatide, and liraglutide from the 503B bulks list — effectively closing the last broad legal path for mass-scale compounded GLP-1 production. Here is what the proposal says, who it affects, and what the enforcement landscape looks like in late 2026.
Orforglipron is the first oral, non-peptide GLP-1 receptor agonist to clear Phase 3. It needs no food or water timing, delivers 12.4% weight loss, and has a PDUFA goal date of April 10, 2026. Here's what the ATTAIN program showed and why pill-form GLP-1 therapy matters.
Eli Lilly's Phase 3 TRIUMPH-1 trial of retatrutide delivered up to 30.3% mean body weight loss at 104 weeks — the highest ever recorded in a pharmacological obesity trial. Here is what the data show, how it compares to tirzepatide and semaglutide, and what it means for the peptide landscape in 2026.
Semaglutide is a GLP-1 receptor agonist originally developed for type 2 diabetes. This overview covers the clinical research behind its metabolic and weight-related effects.
GLP-1 receptor agonists are peptides that mimic the native hormone glucagon-like peptide-1. They slow gastric emptying, promote satiety, and increase glucose-dependent insulin secretion. The class includes semaglutide (Ozempic/Wegovy), tirzepatide (Mounjaro/Zepbound — a dual GLP-1/GIP agonist), and retatrutide (an investigational triple agonist).
Semaglutide is a selective GLP-1 agonist. Tirzepatide adds GIP receptor activity, producing larger weight loss in head-to-head trials (SURMOUNT vs STEP). Retatrutide is a triple agonist adding glucagon receptor activity — Phase 3 TRIUMPH-1 data show ~30% body-weight loss at the top dose, the largest observed to date for any obesity pharmacotherapy.
Nausea, constipation, diarrhea, and injection-site reactions are the most frequently reported. These are typically dose-dependent and improve with gradual titration. See our side-effect deep dives for strategies to manage each.