Semaglutide is a GLP-1 receptor agonist made by Novo Nordisk and sold as Ozempic (type 2 diabetes), Wegovy (chronic weight management) and Rybelsus (oral tablet for diabetes). It is a fully approved prescription medicine in the UK, US and EU, with large randomised trials showing meaningful weight loss and reduced cardiovascular and kidney events. It is not a research chemical.
Tirzepatide is a once-weekly injectable medicine made by Eli Lilly, approved for type 2 diabetes (as Mounjaro) and chronic weight management (as Zepbound). It activates two gut-hormone receptors at once — GIP and GLP-1 — and in head-to-head trials produced greater weight loss and A1c reduction than GLP-1-only drugs like semaglutide.
Both peptides share an evidence grade of A. The right choice depends less on the data and more on what you're trying to do — Semaglutide for type 2 diabetes, Tirzepatide for type 2 diabetes.
FDA-approved 2017 and EMA-approved 2018 as Ozempic; oral Rybelsus approved 2019. Indicated alongside diet and exercise to improve glycaemic control in adults with type 2 diabetes.
Wegovy (semaglutide 2.4 mg) is FDA-approved (2021) and EMA-approved (2022) for chronic weight management in adults with obesity, or overweight with at least one weight-related comorbidity. NICE recommends it within specialist services for up to two years.
Approved to reduce the risk of major adverse cardiovascular events in adults with type 2 diabetes plus established cardiovascular disease (Ozempic), and — based on SELECT — in adults with obesity or overweight plus established cardiovascular disease without diabetes (Wegovy, 2024).
FDA-approved 2022 and EMA-approved 2022 as Mounjaro, as an adjunct to diet and exercise to improve blood-sugar control in adults with type 2 diabetes. The SURPASS programme demonstrated superior A1c reduction versus comparators across five phase-3 trials.
FDA-approved 2023 as Zepbound and authorised in the UK/EU under Mounjaro, for adults with obesity (BMI ≥30) or overweight with a weight-related comorbidity. SURMOUNT-1 showed mean weight reductions up to 22.5% at 72 weeks.
FDA-approved in 2024 (as Zepbound) for moderate-to-severe OSA in adults with obesity, on the basis of the SURMOUNT-OSA trials, which showed clinically meaningful reductions in apnoea-hypopnoea index.
The commonest side effects are gastrointestinal — nausea, vomiting, diarrhoea, constipation, abdominal pain — typically worst during dose escalation and easing over time. Most are mild to moderate; a minority of patients discontinue because of them. More serious risks on the label include pancreatitis (rare), gallbladder disease (semaglutide modestly increases the rate of cholelithiasis), and acute kidney injury usually mediated by dehydration from vomiting. The FDA label carries a boxed warning for thyroid C-cell tumours based on rodent data; whether this translates to humans is unresolved, but the medicine is contraindicated in anyone with a personal or family history of medullary thyroid carcinoma or MEN 2 syndrome. The EMA confirmed in 2025 that NAION (a rare optic-nerve condition causing sudden vision loss) is a very rare side effect. Not for use in pregnancy or breastfeeding. Counterfeit semaglutide and unregulated compounded versions have caused serious harm — only use a regulated pharmacy supply.
The most common side effects are gastrointestinal: nausea, diarrhoea, constipation, vomiting and reduced appetite — usually mildest during dose titration and easing over time. Serious but less common risks flagged on the FDA label include pancreatitis, gallbladder disease, acute kidney injury (often via dehydration), and severe hypersensitivity reactions. Tirzepatide carries a boxed warning for thyroid C-cell tumours based on rodent data and is contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN-2 syndrome. It is not recommended in pregnancy. Long-term safety beyond a few years is still being characterised.
Both peptides share an evidence grade of A. The right choice depends less on the data and more on what you're trying to do — Semaglutide for type 2 diabetes, Tirzepatide for type 2 diabetes.
Pepwyse comparison pages are generated from the same structured data behind each peptide profile. Want a different head-to-head? Use the compare picker or ask Semaglutide directly via the Ask-Peppy button. Not medical advice — see how we grade evidence.