Common claims about GLP-1s, checked against the sources

Each claim below is something a first-time reader is likely to hear from a friend, a forum or an advert. The check is against a label, a trial paper or an FDA page, and nothing else.

1. "It only works if you feel sick."

False. Nausea was reported by 44% of people on Wegovy 2.4 mg and 25 to 29% on Zepbound in the label tables (section 6.1), which means most people on Zepbound and more than half on Wegovy did not report it, and the trials measured weight loss across everyone. Nausea is a side effect of the mechanism, not a measure of it.

2. "Ozempic is approved for weight loss."

False. The Ozempic label is for adults with type 2 diabetes, with two further indications in that population (section 1). Semaglutide for weight management is Wegovy, a separate approval at a higher dose. The same applies to Mounjaro and Zepbound.

3. "You can start higher to speed things up."

False, and the labels say why. Every label starts at the same initiation dose and holds it for four weeks to reduce gastrointestinal reactions (section 2.1). FDA's page on unapproved GLP-1 products describes adverse event reports involving compounded products where dosing exceeded the label or escalated faster than the label schedule, with nausea and vomiting as the result.

4. "The weight comes straight back when you stop."

More true than people expect, with numbers. In the STEP 1 extension, participants who stopped semaglutide and the lifestyle programme after 68 weeks had regained about two thirds of their lost weight one year later (PubMed 35441470). In SURMOUNT-4, people switched from tirzepatide to placebo after 36 weeks regained a mean 14% of body weight over the next 52 weeks, while those who continued lost a further 5.5% (PubMed 38078870). Not "straight back" and not everyone, but the direction is clear. Both labels indicate the drugs for long-term use, and the Weight Loss on GLP-1s site covers maintenance planning.

5. "It is a shortcut; you do not have to change anything."

Not what the trials tested. Every participant in STEP 1 and SURMOUNT-1 was on a reduced-calorie diet and an activity programme with counselling, and the placebo groups lost 2.4% and 3.1% on that alone (PubMed 33567185; PubMed 35658024). The labels indicate the drugs in combination with a reduced-calorie diet and increased physical activity. What the drug changes is how hard that is.

6. "Compounded is the same drug, just cheaper."

False as stated. Compounded semaglutide and tirzepatide are not FDA approved, are not reviewed for safety, effectiveness or quality before sale, and FDA has found some made with salt forms that differ from the approved active ingredient (FDA, Human Drug Compounding; FDA's Concerns page). They are not interchangeable with brand products. FormBlends, which runs this site, sells compounded products; see the brand versus compounded page for the full disclosure and what the difference means in practice.

7. "It causes thyroid cancer."

Unknown in humans; the label says so. The boxed warning states that semaglutide and tirzepatide caused thyroid C-cell tumors in rodents and that it is unknown whether they cause them, including medullary thyroid carcinoma, in humans. The drugs are contraindicated in people with a personal or family history of MTC or MEN 2 (section 4). Both halves matter: the risk is not established, and the exclusion is real.

8. "You have to inject it in your stomach."

False. The labels allow abdomen, thigh or upper arm, and ask you to rotate sites (section 2). See your first injection.

9. "Everyone loses 15 to 20 percent."

Averages, not guarantees. 14.9% was the mean at 68 weeks in STEP 1; 13.6% of the semaglutide group did not reach 5%. 15.0 to 20.9% were the means at 72 weeks in SURMOUNT-1 by dose; 9 to 15% did not reach 5%. The when weight change starts page has the responder rates.

10. "It is dangerous to eat normally around surgery on it."

Half true, and the half that is true matters. The labels warn about pulmonary aspiration during general anesthesia or deep sedation because the drug slows stomach emptying, and they tell you to inform the team performing the procedure (section 5). The action is not to change your diet; it is to tell the anaesthetist and ask your prescriber whether to pause before the date.

What to do with a claim not on this list

Ask where it comes from. If the answer is a label section, a PubMed id or an FDA page, it can be checked. If it is a screenshot, treat it as a question for your prescriber. The network's Research site has the trial numbers and the encyclopedia has the label facts for every agent.