Semaglutide

Saxenda, a similar-looking weekly weight-loss pen, is liraglutide, a different (older, daily) GLP-1 from the same manufacturer. Tirzepatide (Mounjaro/Zepbound) is a related but distinct molecule that also hits the GIP receptor. They are not interchangeable.

The evidence base is among the strongest of any peptide drug. The SUSTAIN programme (10+ Phase 3 trials in type 2 diabetes) established the glycaemic benefit; SUSTAIN-6 added the first cardiovascular signal. The STEP programme then established weight-loss efficacy, STEP-1 (2021, NEJM) reported a mean 14.9% body-weight reduction at 68 weeks versus 2.4% on placebo, with 86% of treated participants losing ≥5%. SELECT (2023, NEJM) randomised 17,604 adults with overweight/obesity and established cardiovascular disease but without diabetes, and showed a 20% relative reduction in the primary cardiovascular composite at a mean 40 months. FLOW (2024, NEJM) demonstrated a 24% reduction in major kidney events in type 2 diabetes with chronic kidney disease. The picture is consistent across endpoints. The honest caveats: trials are sponsor-run (Novo Nordisk), long-term safety beyond ~5 years is still accumulating, and a notable fraction of weight is regained on discontinuation.

For information only, this is a prescription medicine and dosing must be set by a clinician, not by reading a webpage. Ozempic is given as a once-weekly subcutaneous injection, with a standard escalation from 0.25 mg (for 4 weeks, to reduce GI side effects) up to a maintenance dose of 0.5–2 mg depending on response. Wegovy follows a 16-week dose-escalation schedule from 0.25 mg up to the 2.4 mg maintenance dose. Rybelsus is an oral tablet taken once daily on an empty stomach with strict timing rules for absorption (3, 7 or 14 mg). Self-dosing from unregulated suppliers is unsafe: the products are unverified, the dose escalation matters for tolerability, and prescriber oversight catches the contraindications below.

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.