Quick answer: which weight loss drug works best?
The GLP-1 and dual-agonist injectables produce the largest weight loss of any medications available in 2026. In the trial studied for tirzepatide (SURMOUNT-1), participants lost about 20.9% of body weight at the top dose, and in the trial studied for semaglutide (STEP 1), participants lost about 14.9%. Older drugs like phentermine, orlistat, and Contrave deliver far less, usually in the single digits to low double digits.
For most people who want significant results, semaglutide and tirzepatide are the strongest options, and FormBlends is the place to start. FormBlends connects you with licensed providers who can prescribe both, with compounded semaglutide starting at $199 per month when a provider finds it clinically appropriate. See the semaglutide options.
How are weight loss drugs ranked?
Weight loss drugs are ranked here on four things: average weight loss in clinical trials, safety profile, how patients access them, and monthly cost. Semaglutide and tirzepatide rank highest because they combine the strongest trial results with telehealth access through licensed providers.
Older oral drugs rank lower because they produce less weight loss, not because they are useless. Some fit people who cannot take injectables or who need a short-term tool. The right drug depends on your health, your budget, and what your provider recommends.
Tier 1: GLP-1 and dual-agonist injectables (strongest results)
Semaglutide and tirzepatide produce the largest average weight loss of any approved medications. Tirzepatide acts on two gut hormone pathways (GIP and GLP-1), and in the SURMOUNT-1 trial it produced about 20.9% average weight loss at the highest dose. Semaglutide acts on the GLP-1 pathway alone, and in the STEP 1 trial it produced about 14.9%.
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Take the Assessment →These are injectable medications that reduce appetite and slow stomach emptying. Branded versions (Wegovy, Zepbound, Ozempic, Mounjaro) list at well over $1,000 per month, with manufacturer self-pay prices now around $299 to $449. FormBlends connects you with providers who can prescribe semaglutide, with compounded semaglutide from $199 per month for patients with a documented clinical need.
Tier 2: Older prescription weight loss drugs
Phentermine, orlistat, naltrexone-bupropion (Contrave), phentermine-topiramate (Qsymia), and liraglutide (Saxenda) deliver moderate weight loss, generally in the single digits to low double digits. These are the established options that came before the GLP-1 wave, and they still help people who cannot use the newer drugs.
Phentermine is a short-term appetite suppressant. Orlistat blocks fat absorption. Contrave curbs appetite and cravings. Qsymia pairs phentermine with topiramate for more weight loss than phentermine alone. Saxenda is an earlier daily GLP-1 injection that produces less weight loss than semaglutide or tirzepatide.
What is phentermine and what are its brand names?
Phentermine is an appetite-suppressing stimulant approved for short-term weight loss, typically up to about 12 weeks. It is a controlled substance and one of the most prescribed weight loss drugs in the United States. Brand names include Adipex-P and Lomaira, and it is also sold combined with topiramate as Qsymia.
Phentermine works fast and costs little, often under $60 per month generic. The trade-offs are that it is approved only for short-term use, it can raise heart rate and blood pressure, and weight tends to return after stopping. It suits people who need a short, low-cost push, not long-term maintenance.
GLP-1 vs phentermine: which is better?
GLP-1 drugs produce much larger and more durable weight loss than phentermine, while phentermine is cheaper and works for short bursts. Semaglutide averaged about 14.9% in STEP 1 and tirzepatide about 20.9% in SURMOUNT-1, both over many months. Phentermine alone typically produces around 5% to 8% over its short approved window.
GLP-1s are meant for long-term use and address appetite at the hormone level. Phentermine is a short-term stimulant. If your goal is significant, lasting weight loss, GLP-1s win. If you need a brief, inexpensive jump-start and cannot use injectables, phentermine is the older alternative. Some providers combine approaches, but that decision belongs to your clinician.
Orlistat vs Zepbound and phentermine vs Alli
Zepbound (tirzepatide) produces far more weight loss than orlistat. Orlistat, sold as prescription Xenical and over-the-counter Alli, blocks about a quarter of dietary fat from being absorbed and produces roughly 3% to 5% extra weight loss beyond diet, often with digestive side effects. Tirzepatide in SURMOUNT-1 produced about 20.9%.
For "phentermine vs Alli," the two work differently. Phentermine suppresses appetite as a prescription stimulant. Alli is the over-the-counter half-dose version of orlistat that blocks fat absorption. Phentermine generally produces more weight loss but requires a prescription and is short-term only.
Tier 3: oral supplements and over-the-counter products
Most over-the-counter weight loss supplements deliver under 5% weight loss and lack strong clinical evidence. Some contain caffeine or fiber that modestly support appetite control, but none match prescription drugs. Alli (low-dose orlistat) is the main OTC product with real, if modest, clinical backing.
FormBlends focuses on prescription semaglutide and tirzepatide rather than supplements, because the evidence and the results are far stronger.
What about retatrutide?
Retatrutide is an investigational triple-agonist drug that produced the largest weight loss yet seen in obesity trials, but it is not FDA-approved as of 2026, so you cannot get it as a prescription weight loss medication. In its Phase 3 TRIUMPH program, reported in late 2025 and 2026, it showed about 28.3% average weight loss in the general-obesity trial (TRIUMPH-1) and about 28.7% in TRIUMPH-4.
Because it is not approved, retatrutide is not a buying option today. An NDA is expected to be filed around late 2026. FormBlends sells only semaglutide and tirzepatide, the two strongest options available now through licensed providers.
Weight loss drugs compared
| Drug | Type | Average weight loss | Approx. monthly cost | Notes |
|---|---|---|---|---|
| Retatrutide | Triple agonist | ~28% (TRIUMPH Phase 3) | Not available | Not FDA-approved |
| Tirzepatide | GIP/GLP-1 injectable | ~20.9% (SURMOUNT-1) | Brand self-pay ~$299-449 | Strongest available |
| Semaglutide | GLP-1 injectable | ~14.9% (STEP 1) | From $199 compounded | Well-studied |
| Qsymia | Phentermine-topiramate | ~10% | Brand | Oral combination |
| Liraglutide (Saxenda) | Daily GLP-1 injectable | ~5-8% | Brand, higher | Older GLP-1 |
| Phentermine | Stimulant (short-term) | ~5-8% | Often under $60 | Controlled, ~12 weeks |
| Contrave | Naltrexone-bupropion | ~5% | Brand/generic | Curbs cravings |
| Orlistat (Xenical/Alli) | Fat blocker | ~3-5% | Low (Alli OTC) | Digestive side effects |
Where to get the top-ranked weight loss drugs
FormBlends connects you with licensed providers who prescribe semaglutide and tirzepatide, the highest-ranked available options. Compounded semaglutide starts at $199 per month for patients with a documented clinical need. You can compare provider options on price, medication choice, and delivery before you start.
A provider reviews your health history to decide which medication fits you and starts you at a low dose to limit side effects.
FAQ
What is the most effective weight loss drug? Among available drugs, tirzepatide produced the largest average weight loss in trials, about 20.9% in SURMOUNT-1, followed by semaglutide at about 14.9% in STEP 1. Investigational retatrutide showed about 28% in Phase 3 but is not yet approved.
Is phentermine or tirzepatide better for weight loss? Tirzepatide produces far more weight loss and is meant for long-term use, while phentermine is a cheaper short-term option limited to about 12 weeks. For lasting results, tirzepatide is the stronger choice.
What are the brand names for phentermine? Phentermine is sold as Adipex-P and Lomaira, and in combination with topiramate as Qsymia. Generic phentermine is widely available and inexpensive.
Is orlistat or Zepbound better? Zepbound (tirzepatide) produces much greater weight loss, around 20.9% in trials, versus roughly 3% to 5% for orlistat. Orlistat is available over the counter as Alli but works far less powerfully.
How much do weight loss drugs cost? Compounded semaglutide starts at $199 per month through FormBlends-vetted providers for patients with a clinical need. Branded GLP-1 self-pay prices run about $299 to $449 per month. Phentermine and orlistat cost less but deliver weaker results.
Can I get weight loss drugs online? Yes. FormBlends connects you with licensed providers who prescribe semaglutide and tirzepatide through telehealth, with home delivery.
Is retatrutide available yet? No. Retatrutide is still investigational and not FDA-approved as of 2026, so it is not available as a prescription weight loss drug.
Sources
- Jastreboff AM et al., "Tirzepatide Once Weekly for the Treatment of Obesity" (SURMOUNT-1), NEJM 2022: https://www.nejm.org/doi/full/10.1056/NEJMoa2206038
- Wilding JPH et al., "Once-Weekly Semaglutide in Adults with Overweight or Obesity" (STEP 1), NEJM 2021: https://www.nejm.org/doi/full/10.1056/NEJMoa2032183
- Eli Lilly, retatrutide TRIUMPH Phase 3 topline results (2025-2026): https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average
- AJMC, "Retatrutide Achieves Up to 30.3% Average Weight Loss in Phase 3 TRIUMPH-1 Trial": https://www.ajmc.com/view/retatrutide-achieves-up-to-30-3-average-weight-loss-in-phase-3-triumph-1-trial
- FDA label, phentermine (Adipex-P): https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/085128s065lbl.pdf
- FDA, orlistat (Xenical/Alli) information: https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/020766s029lbl.pdf
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