Fact check
Fact-checked by Dr. Adam Kennah, MD on . See our fact-checking policy.
Ten of the most common claims patients encounter about GLP-1 medications, rated against the underlying evidence. Each claim is reviewed against peer-reviewed trials, FDA labeling, or regulatory guidance — not against social-media consensus.
What the evidence shows: GLP-1s slow gastric emptying as part of their mechanism. Symptomatic gastroparesis is a rare adverse event, and the slowing typically reverses after discontinuation. FDA added gastroparesis to the Ozempic label in 2023 as a potential adverse reaction, not as a permanent effect.
What the evidence shows: Compounded semaglutide may contain the same active pharmaceutical ingredient (semaglutide) but is not FDA-approved as a finished drug product, is not bioequivalence-tested against Ozempic, and is prepared under different regulatory standards (503A/503B vs. cGMP for FDA-approved drugs).
What the evidence shows: Multiple trials (STEP-4, STEP-1 extension) show significant weight regain after discontinuation, though typically not 100% of lost weight in the first year. The STEP-4 trial demonstrated that switching from semaglutide 2.4 mg to placebo resulted in regain of approximately two-thirds of lost weight by week 68.
What the evidence shows: GLP-1 RAs carry a boxed warning based on thyroid C-cell tumors observed in rodent studies. The link to human medullary thyroid carcinoma is not established; the warning is precautionary. Patients with personal or family history of MTC or MEN 2 should not use GLP-1 RAs.
What the evidence shows: GLP-1 RAs reduce appetite through central nervous system mechanisms (hypothalamic activation), slow gastric emptying, and modulate reward pathways. Weight loss occurs even in patients who do not experience nausea. Tolerance to nausea typically develops within 4-8 weeks while weight loss continues.
What the evidence shows: Coverage varies widely. Many commercial plans exclude weight-loss medications entirely. Medicare Part D is statutorily prohibited from covering weight-loss drugs (the Medicare Modernization Act of 2003). State Medicaid coverage is inconsistent. Prior authorization is typical, and step therapy may be required.
What the evidence shows: Compounded GLP-1 medications remain legal under FD&C Act section 503A when a licensed prescriber documents medical necessity for the individual patient. FDA's 2025 guidance ended broad enforcement discretion that had applied during the shortage, not the underlying legal pathway for compounding.
What the evidence shows: Products sold as 'research peptides' or 'not for human consumption' semaglutide are not prepared under sterile compounding standards, are not tested for endotoxin (USP <85>), are frequently counterfeited, and are not sold through a licensed pharmacy. Multiple FDA warning letters have been issued against such sellers.
What the evidence shows: Tirzepatide is a structurally distinct molecule that activates both the GIP receptor and the GLP-1 receptor (dual GIP/GLP-1 agonist). Semaglutide activates only the GLP-1 receptor. Different molecules, different manufacturers (Eli Lilly vs. Novo Nordisk), different efficacy profiles.
What the evidence shows: Every pivotal Phase 3 trial of GLP-1 RAs for weight loss included a behavioral intervention (reduced-calorie diet plus increased physical activity) in both treatment and placebo arms. The medication's effect is added on top of behavioral change, not a replacement for it.