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By HealthVetted Editorial
Reviewed & updated
GLP-1 medications are the most effective prescription tools for weight loss approved to date, and demand has reshaped how people approach obesity care. This guide explains what these drugs are, which ones are FDA-approved for weight management, how much weight they help people lose in clinical trials, who qualifies, what they cost, and what the trade-offs are — with every clinical figure linked to a primary source.
We sell nothing we review and take no payment for placement. For our ranked picks, see [best prescription GLP-1 medications](/best-prescription-glp1); for the broader treatment landscape including non-drug options, see our [weight-loss condition guide](/conditions/weight-loss).
GLP-1 receptor agonists are injectable or oral drugs that mimic glucagon-like peptide-1, a hormone your gut releases after eating. They slow how fast the stomach empties, blunt appetite and "food noise," and improve how the body handles blood sugar. Tirzepatide additionally activates a second hormone receptor (GIP), which is one reason it produces larger average weight loss than semaglutide in head-to-head trial data.
These are not appetite-suppressant supplements or stimulants. They are prescription drugs that change the hormonal signals controlling hunger and satiety, which is why their effect sizes are far larger than [over-the-counter weight-loss supplements](/supplements-vs-glp1).
The same active ingredient is often sold under two brand names — one approved for type 2 diabetes, one for chronic weight management.
| Active ingredient | Weight-management brand | Diabetes brand | Route |
|---|---|---|---|
| Semaglutide | Wegovy (FDA-approved for weight) | Ozempic | Weekly injection |
| Tirzepatide | Zepbound (FDA-approved for weight) | Mounjaro | Weekly injection |
| Semaglutide (oral) | — | Rybelsus | Daily tablet |
Wegovy ([semaglutide](/reviews/wegovy)) and Zepbound ([tirzepatide](/reviews/zepbound)) carry FDA approval specifically for chronic weight management. Ozempic and Mounjaro contain the same molecules but are FDA-approved for type 2 diabetes; prescribing them for weight loss alone is off-label. Oral GLP-1 options are expanding — see [best oral GLP-1 options](/best-oral-glp1) and, for lower-cost routes, [compounded GLP-1](/best-compounded-glp1).
Effect sizes come from large randomized trials, not marketing:
Individual results vary widely around those averages, and weight loss depends on reaching and tolerating the target dose. Both drugs are titrated slowly over months to limit side effects. For a side-by-side, compare [Wegovy vs Zepbound](/compare/wegovy-vs-zepbound).
Per the FDA labels and NIDDK guidance, these drugs are indicated for adults with a body mass index (BMI) of 30 or higher, or 27 or higher with at least one weight-related condition such as high blood pressure, type 2 diabetes, or high cholesterol. A clinician confirms eligibility, screens for contraindications, and writes the prescription. You can estimate your starting point with our [GLP-1 eligibility quiz](/tools/glp1-eligibility-quiz).
List prices for branded GLP-1s are high — roughly four figures per month before insurance, savings programs, or compounding. What you actually pay varies enormously by coverage, manufacturer programs, and pharmacy route, and those terms change often. Rather than quote a promo price that may be stale, estimate your real cost with the [GLP-1 cost calculator](/tools/glp1-cost-calculator), and compare lower-cost routes in [compounded GLP-1](/best-compounded-glp1).
The most common side effects are gastrointestinal: nausea, vomiting, diarrhea, and constipation. They are usually worst early and after dose increases, and ease as the body adjusts — which is why dosing starts low and steps up slowly.
These drugs carry a boxed warning for thyroid C-cell tumors based on rodent studies, and are contraindicated in people with a personal or family history of medullary thyroid carcinoma or MEN 2. Tell your prescriber about every medication you take, and check interactions with our [interaction checker](/tools/interaction-checker). This is general information, not medical advice — decisions belong with your clinician.
Obesity is a chronic condition, and GLP-1 medications manage it rather than cure it. In trials and clinical practice, stopping the drug is typically followed by a return of appetite and substantial regain of the lost weight, because the hormonal signal that suppressed hunger is gone. That makes the long-term plan — maintenance dosing, cost sustainability, and lifestyle support — part of the decision from day one, not an afterthought.
No over-the-counter supplement comes close to the trial-validated effect sizes above. Some have modest or mixed evidence; many have little. We lay out the honest gap in [supplements vs GLP-1](/supplements-vs-glp1) and [berberine vs Ozempic](/berberine-vs-ozempic). If a prescription isn't right for you, those guides cover what the evidence does and doesn't support.
GLP-1 medications are the most effective approved drugs for weight loss, with semaglutide and tirzepatide producing roughly 15% and 21% average body-weight loss in trials. They require a prescription, carry real (mostly gastrointestinal) side effects and a boxed warning, cost meaningfully, and work only while you take them. For our ranked, independently scored picks, start with [best prescription GLP-1 medications](/best-prescription-glp1).
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In trial averages, tirzepatide (Zepbound) produced more weight loss (~21%) than semaglutide (Wegovy, ~15%), but the right choice depends on tolerability, cost, insurance, and your clinician’s assessment. See our ranked picks at /best-prescription-glp1.
Both are semaglutide. Wegovy is FDA-approved for chronic weight management at higher doses; Ozempic is approved for type 2 diabetes. Using Ozempic for weight loss alone is off-label.
Yes. GLP-1 receptor agonists are prescription drugs. A licensed clinician confirms eligibility (typically BMI ≥30, or ≥27 with a weight-related condition) and screens for contraindications.
Appetite returns and much of the lost weight is typically regained, because the medication manages a chronic condition rather than curing it. A long-term maintenance plan should be part of the decision.