The GLP-1 guide
How GLP-1 and dual-agonist medications work, what the human trials actually show, the difference between the brands, and why the titration is slow — with sources. Not medical or dosing advice.
How GLP-1 medications work
GLP-1 (glucagon-like peptide-1) is a gut hormone that boosts glucose-dependent insulin release, slows gastric emptying, and reduces appetite signalling. The drugs are long-acting analogues that engage that pathway. Tirzepatide adds GIP-receptor activity (a second incretin), which is why it's called a dual agonist. These mechanisms are well characterized — this is real pharmacology, not a research-peptide hypothesis.
What the trials show
- Semaglutide (STEP program). Large randomized weight-management trials in adults without diabetes.
- Tirzepatide (SURMOUNT / SURPASS). Randomized trials for weight and for glycemic control.
- Effect varies by person. Trial averages aren't a promise for any individual — and results depend on staying on therapy.
Why the titration is slow
Every GLP-1 label starts low and steps up over weeks. That's to limit nausea and GI effects while the body adjusts — not an arbitrary schedule. The titration calculator maps the manufacturer's labeled steps to dates; the pen guide explains the device mechanics. Neither is a recommendation — follow your prescriber and the label.
Frequently asked questions
What's the difference between Ozempic, Wegovy, Mounjaro and Zepbound?
Ozempic and Wegovy are both semaglutide (a GLP-1 agonist) — Ozempic is labeled for type-2 diabetes, Wegovy for weight management, with different titration. Mounjaro and Zepbound are both tirzepatide (a dual GIP/GLP-1 agonist) — Mounjaro for diabetes, Zepbound for weight. Same molecules, different indication and labeled schedule.
Is tirzepatide better than semaglutide?
Head-to-head and program data suggest tirzepatide produces larger average weight reduction, but “better” depends on the individual, tolerability, cost, and goal. Both are strongly evidenced relative to almost everything else marketed for weight. This is general information, not a recommendation — that's a prescriber conversation.
Why do I have to increase the dose slowly?
The labels escalate over weeks to reduce nausea, vomiting, and other GI effects while the body adapts. Moving faster than the labeled schedule tends to worsen side effects. The titration calculator shows the standard manufacturer steps for reference; your prescriber may adjust the timing.
Are compounded GLP-1s the same as the real thing?
No. Compounded or research-labeled versions are not the FDA-approved products and aren't held to the same manufacturing, identity, and purity standards. Salt forms and unverified sources are common concerns. If you use any product, the approved, prescribed version is the only one with the trial evidence behind it.
What happens if I stop?
Appetite and weight effects depend on continued treatment for most people; stopping commonly leads to regain over time. How to start, continue, or stop is an individual medical decision — we don't advise on it.
Sources
- [1]Wilding JPH et al. — Once-weekly semaglutide in adults with overweight or obesity (STEP 1) — N Engl J Med, 2021
- [2]Jastreboff AM et al. — Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1) — N Engl J Med, 2022
- [3]Wegovy (semaglutide) — FDA prescribing information — U.S. FDA / DailyMed
- [4]Ozempic (semaglutide) — FDA prescribing information — U.S. FDA / DailyMed
- [5]Mounjaro / Zepbound (tirzepatide) — FDA prescribing information — U.S. FDA / DailyMed
Links resolve to authoritative search or landing pages (PubMed, FDA / DailyMed). See the full source library and methodology.
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Start here →Educational and research reference only. Not medical advice, diagnosis, or dosing guidance.