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Health & tracking · updated 2026

Illustration of GLP-1 signaling pathways in the body

Understanding GLP-1s: how they work, what's approved, and what to know

Quick answer: GLP-1 medications are lab-made versions of a natural gut hormone that increase insulin release, slow digestion, and reduce appetite. They're FDA-approved for type 2 diabetes and, in specific formulations, chronic weight management. Ozempic and Wegovy contain the same drug (semaglutide); Mounjaro and Zepbound contain the same drug (tirzepatide) — the difference between each pair is the approved use, not the medication itself.

What GLP-1 actually stands for

GLP-1 stands for glucagon-like peptide-1 — a hormone your intestines release naturally after you eat. It's part of your body's own system for managing blood sugar and appetite. GLP-1 medications ("GLP-1 receptor agonists") are synthetic versions engineered to do the same job, but for longer — natural GLP-1 breaks down in minutes; the medication versions are modified to last up to a week per dose.

How GLP-1 medications work in the body

Once injected (or, for one option, swallowed), the medication attaches to GLP-1 receptors in three main places:

The pancreas — triggers insulin release, but only when blood sugar is already elevated, which is why these medications carry a lower risk of dangerously low blood sugar than older diabetes drugs.
The brain (hypothalamus) — reduces hunger signals and increases the feeling of fullness.
The stomach — slows how quickly food empties into the intestine, extending the feeling of satiety after eating. This same mechanism is also the main source of the nausea and digestive side effects people report.

What's actually FDA-approved right now

Several brand names exist because the same active ingredient is often approved separately for diabetes and for weight management, under two different names, by the same manufacturer:

Active ingredientDiabetes brandWeight-management brand
SemaglutideOzempicWegovy (also: Rybelsus, the only oral option)
TirzepatideMounjaroZepbound
LiraglutideVictozaSaxenda
DulaglutideTrulicity— (diabetes only)

Tirzepatide (Mounjaro/Zepbound) is technically a dual GIP/GLP-1 receptor agonist — it activates a second hormone pathway (GIP) alongside GLP-1, which is part of why trials have shown it producing somewhat greater average weight loss than semaglutide alone.

Common side effects

The most frequently reported side effects — nausea, constipation, diarrhea, and reflux — trace back to the same mechanism that slows digestion. They tend to show up most after starting the medication or increasing the dose, and often ease as the body adjusts. This is also why what and how much you eat matters more on a GLP-1 than it did before — see our guide on GLP-1 and your cycle for how this connects to hormonal symptoms specifically.

When to actually contact your prescriber: severe abdominal pain (a rare but serious sign that needs prompt evaluation), signs of an allergic reaction, or side effects severe enough to affect eating or hydration for more than a couple of days.

Ozempic vs. Wegovy — the real difference

Same drug, same manufacturer, different FDA-approved use. Ozempic is approved for type 2 diabetes, capped at 2 mg weekly. Wegovy is approved specifically for chronic weight management, capped at a higher 2.4 mg weekly. Many prescribers use Ozempic off-label for weight loss because insurance is more likely to cover a diabetes diagnosis than a weight-management one — that's an insurance and labeling difference, not a difference in what the medication does in your body.

Mounjaro vs. Zepbound — the same pattern

Mounjaro and Zepbound both contain tirzepatide from the same manufacturer. Mounjaro is approved for type 2 diabetes; Zepbound is approved for weight management. As with semaglutide, this is a labeling and insurance distinction, not a different medication.

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This page is general information, not medical advice, and isn't a substitute for care from your doctor or pharmacist. Only your prescriber can tell you which medication, dose, and plan is right for you. If you're experiencing severe side effects, contact your healthcare provider rather than relying on this or any other general guide.