On raw efficacy the answer is settled: tirzepatide — sold as Zepbound (obesity), Mounjaro (diabetes), or compounded — produces the most weight loss of any GLP-1 available in 2026. In SURMOUNT-5, the only head-to-head trial, tirzepatide delivered 20.2% average body weight loss vs semaglutide's 13.7% over 72 weeks. But "best drug" and "best for you" are different questions. The GLP-1 that actually works is the one you can stay on for 12+ months — and real-world data shows 47% of patients quit within a year, mostly over cost, not side effects. A tirzepatide prescription you abandon at month 3 loses to compounded semaglutide you take for two years. So the honest ranking is: tirzepatide if you can access it, semaglutide if it's what your insurance covers or your gut tolerates, and whichever you can afford indefinitely if you're paying cash — $99/mo semaglutide or $125/mo tirzepatide via Trimi, $99/$149 via Embody, or $199/$299 flat via TrimRx (Editor's Choice). Here's every GLP-1 ranked on real trial data, what each costs, and the decision matrix for your situation.
The ranking: every GLP-1 by average weight loss
| Rank | Medication | Molecule | Avg weight loss | Trial | Format |
|---|---|---|---|---|---|
| 1 | Zepbound | Tirzepatide | 20.2-22.5% | SURMOUNT-1 / -5 | Weekly injection |
| 1 | Compounded tirzepatide | Tirzepatide | ~20-22% (same molecule) | — | Weekly injection |
| 2 | Mounjaro (off-label) | Tirzepatide | 20.2-22.5% | SURMOUNT-1 | Weekly injection |
| 3 | Wegovy | Semaglutide | 14.9-16% | STEP-1 / -3 | Weekly injection |
| 3 | Compounded semaglutide | Semaglutide | ~15% (same molecule) | — | Weekly injection |
| 4 | Foundayo (orforglipron) | Orforglipron | 14.7% | ATTAIN | Daily pill |
| 5 | Ozempic (off-label) | Semaglutide | 8-14% | SUSTAIN | Weekly injection |
| 6 | Rybelsus | Semaglutide (oral) | 5-10% | PIONEER | Daily pill |
| 7 | Saxenda | Liraglutide | 6.4% | STEP-8 comparison | Daily injection |
Why Ozempic ranks below Wegovy despite being the same molecule: Ozempic's max dose is 2.0 mg/week (diabetes label); Wegovy goes to 2.4 mg (obesity label). Same drug, one extra rung on the ladder — and it's dosed in a population that loses more. See Ozempic vs Wegovy.
The honest answer: "best" depends on four things
Trial averages are not your result. Four variables move your outcome more than the molecule choice does:
1. Can you get it covered? A $25/mo covered Wegovy beats a $1,089/mo Zepbound you can't sustain. Insurance formulary is the single biggest real-world determinant. 2. Can you tolerate it? ~14% of patients are semaglutide low responders; tirzepatide causes more constipation. The drug you tolerate at full dose beats the "better" one you can't titrate up. 3. Can you afford it for 12+ months? Real-world JAMA data (50,395 patients): 47% quit within a year, ~30% citing cost. Patients who *stayed* 12 months lost 12.4% — those who quit averaged 6.8%. 4. Will you actually inject it? If needles are a hard stop, a 14.7% oral pill you take daily beats a 22% injection sitting in your fridge.
The rule that matters more than the ranking: time on medication predicts results better than molecule choice. Pick the one you'll still be taking next year.
Best by situation — the decision matrix
| Your situation | Best GLP-1 | Why | Cost |
|---|---|---|---|
| Insured, BMI ≥30, want max results | Zepbound | Highest efficacy, on-label, savings card | $25/mo |
| Insured, plan covers Wegovy not Zepbound | Wegovy | On formulary beats theoretically-better | $25/mo |
| Type 2 diabetes + insured | Mounjaro | Best A1C drop (-2.30 vs -1.86 in SURPASS-2) | $25/mo |
| T2D + cardiovascular disease | Ozempic | SELECT trial CV outcome data is the deepest | $25/mo |
| Medicare Part D, qualifying tier | Wegovy or Zepbound | Bridge program | $50/mo |
| Cash-pay, want max weight loss | Compounded tirzepatide | Same molecule as Zepbound | $125-$299/mo |
| Cash-pay, want lowest cost | Compounded semaglutide | Market floor, same molecule as Wegovy | $99/mo |
| Needle-averse | Foundayo (orforglipron) | 14.7%, daily pill, no fasting | $149/mo |
| Failed/plateaued on semaglutide | Tirzepatide | Recruits the GIP pathway semaglutide doesn't | $25-$299/mo |
| Bad constipation on tirzepatide | Semaglutide | GLP-1-only = less GI motility slowdown | $25-$199/mo |
| PCOS, no T2D, BMI <30 | Compounded (either) | Neither brand gets covered | $99-$149/mo |
What each one actually costs
The efficacy ranking inverts when you look at cost. Here's every path:
| Medication | Insured (savings card) | Medicare Bridge | Cash-pay best | Retail |
|---|---|---|---|---|
| Zepbound | $25/mo | $50/mo | $349-$499 (LillyDirect vials) | $1,089/mo |
| Wegovy | $25/mo | $50/mo | $249/mo (NovoCare) | $1,349/mo |
| Mounjaro | $25/mo (T2D) | Not covered | — | $1,069/mo |
| Ozempic | $25/mo (T2D) | Not covered | — | $998/mo |
| Foundayo | $25/mo | $50/mo | $149/mo | $149/mo |
| Compounded tirzepatide | n/a | Not covered | $125-$299/mo | — |
| Compounded semaglutide | n/a | Not covered | $99-$249/mo | — |
The cash-pay reality: brand Zepbound is 8-10× the price of compounded tirzepatide for the identical molecule. If you're paying out of pocket, the "best" drug on the efficacy chart is rarely the best decision. See Zepbound coupon paths and how to get Wegovy cheaper.
Side effects: the tradeoff behind the ranking
More weight loss generally means more GI side effects — but the pattern differs by molecule:
| Side effect | Semaglutide | Tirzepatide |
|---|---|---|
| Nausea | 44% | 18-22% |
| Diarrhea | 30% | 17% |
| Vomiting | 24% | 8-13% |
| Constipation | 24% | 17-25% (worse at max dose) |
Counterintuitive but important: tirzepatide wins on efficacy *and* has lower nausea/vomiting rates than semaglutide. Its signature complaint is constipation, from the GIP receptor's added effect on gut motility. So "more effective = harder to tolerate" isn't true here — the tradeoff is which *type* of GI symptom you'd rather manage. Full protocols: Ozempic side effects and Mounjaro side effects.
Where to get each one
Brand (Zepbound, Wegovy, Mounjaro, Ozempic, Foundayo): through your prescriber + pharmacy with a manufacturer savings card, LillyDirect/NovoCare direct, or the Medicare Bridge if you qualify.
Compounded (same molecules, cash-pay): these tracked US programs use licensed prescribers and FDA-registered 503A pharmacies — ranked by what we'd recommend:
- TrimRx — Editor's Choice. Semaglutide $199/mo, tirzepatide $299/mo, flat at any dose. US prescribers, monthly check-ins, lab monitoring. Flat pricing matters because brand vials step up in price as you titrate.
- Trimi. Semaglutide $99/mo, tirzepatide $125/mo — the cheapest tirzepatide we track.
- Embody. Semaglutide $99/mo, tirzepatide $149/mo. 24/7 clinician messaging.
- Yucca Health. $146/mo semaglutide on a 6-month plan, LegitScript-verified.
- bmiMD. $99/mo, 80,000+ members, 4.9-star average.
- Bodybuilding.com Health+. $99/mo sema, $129 tirz, with microdosing protocols.
Before you buy compounded, read our safety checklist — the molecule is identical to brand, but the source is what determines safety. Full grids: cheapest compounded semaglutide and cheapest compounded tirzepatide.
What about "best weight loss injection" generally?
If you're comparing injections beyond the GLP-1 class: nothing else is close. Older options — Saxenda (liraglutide, 6.4%), phentermine (~5%), Contrave (~5%), orlistat (~3%) — produce a fraction of tirzepatide's 20-22%. Bariatric surgery still exceeds GLP-1s (25-30%) but carries surgical risk and permanence. For pharmacotherapy in 2026, the GLP-1 class is the answer, and tirzepatide leads it.
FAQ
What is the most effective GLP-1 for weight loss? Tirzepatide (Zepbound, Mounjaro, or compounded) — 20.2% vs semaglutide's 13.7% in the SURMOUNT-5 head-to-head trial at 72 weeks. It's the most effective GLP-1 available in 2026.
Is Zepbound better than Wegovy? On average weight loss, yes — roughly 20-22% vs 15%. But Wegovy is better *for you* if it's the one your insurance covers, or if you tolerate semaglutide better. See our Zepbound vs Wegovy comparison.
Which GLP-1 has the fewest side effects? Tirzepatide actually has lower nausea (18-22% vs 44%), diarrhea, and vomiting rates than semaglutide — but more constipation. There's no clear "gentlest" option; it depends which symptom you'd rather manage.
What's the best GLP-1 if I'm paying cash? Compounded — same molecules at a fraction of brand pricing. Compounded tirzepatide from $125/mo (Trimi) for max efficacy, or compounded semaglutide from $99/mo (Embody, bmiMD) for the lowest cost.
What's the best GLP-1 pill? Foundayo (orforglipron) — 14.7% average weight loss, once daily, no fasting requirement. It beats Rybelsus (5-10%, requires a 30-minute fast). See our Foundayo guide.
Should I switch to tirzepatide if semaglutide isn't working? Often yes. Tirzepatide activates the GIP receptor in addition to GLP-1, so it recruits a pathway semaglutide doesn't — roughly 60-70% of semaglutide low responders do well on it. Start at 2.5 mg regardless of your semaglutide dose. See tirzepatide vs semaglutide.
Is compounded as effective as brand? The active molecule is identical, so clinical effect depends on dose, adherence, and titration — not on who compounded it. Real-world adherence is often *higher* on compounded programs because the cost barrier is lower, and time on medication is what drives results.
How much weight will I actually lose? Trial averages assume you titrate fully and stay on. Real-world 12-month average is 6.8% because half of patients quit early; those who stayed the full year averaged 12.4%. See our realistic week-by-week timeline.
For our full provider rankings see the best GLP-1 programs page and cheapest programs grid. For the molecule-level deep dive, see tirzepatide vs semaglutide. For dosing schedules across every drug here, see our GLP-1 dosage chart.