By average weight loss in clinical trials, tirzepatide (Zepbound) leads at roughly 20% of body weight, ahead of semaglutide 2.4 mg (Wegovy) at about 15% and liraglutide (Saxenda) at about 5–8%. But "best" isn't only the biggest number: tolerability, dosing, cost and insurance coverage all matter, and only Wegovy, Zepbound and Saxenda are FDA-approved specifically for weight management. The right pick is individual and made with a clinician.
Key takeaways
- Average trial loss: Zepbound ~20% > Wegovy ~15% > Saxenda ~5–8%.
- Only Wegovy, Zepbound and Saxenda are FDA-approved for weight management.
- "Best" also weighs side effects, cost, coverage and availability.
- Individual results vary widely; this is education, not a recommendation.
The short answer, by the numbers
If the only thing that mattered were average weight loss in trials, the ranking is clear: tirzepatide first, semaglutide second, liraglutide third. Those averages come from the large pivotal trials (SURMOUNT for tirzepatide, STEP for semaglutide, SCALE for liraglutide), each run alongside diet and activity changes over roughly 16–18 months. They're averages, though — some people lose more, a minority respond poorly. Use our weight-loss calculator to see an illustrative range for your weight.
Side-by-side
| Drug | Molecule | Avg trial weight loss | Approved for weight loss? |
|---|---|---|---|
| Zepbound | Tirzepatide (GIP/GLP-1) | ~20% | Yes |
| Wegovy | Semaglutide | ~15% | Yes |
| Saxenda | Liraglutide | ~5–8% | Yes |
| Ozempic / Mounjaro | Semaglutide / tirzepatide | (diabetes brands) | Used off-label |
Why "best" isn't just the biggest number
The highest average loss doesn't automatically make a drug right for you. A few things can matter just as much:
- Tolerability. If a drug's side effects are rough for you, the "best" one is the one you can actually stay on.
- Cost and coverage. The cheapest covered option you can sustain often beats a pricier one you can't afford long term. See our cost guide.
- Dosing and availability. Weekly injections, titration schedules and supply can all factor in.
- Your response. People vary; the average doesn't predict any one person's result.
Are the side effects different?
Broadly, no — all of these drugs share the same core GLP-1 side-effect profile, driven by slowed stomach emptying: nausea, constipation or diarrhoea, and reflux, worst when starting or raising a dose and usually easing with time. Because tirzepatide tends to push to higher effect, some people find its gastrointestinal effects more noticeable, but tolerability is highly individual and often comes down to how slowly you titrate rather than which molecule it is. The serious-but-rare warnings (pancreatitis, the thyroid C-cell boxed warning) apply across the class. The practical takeaway: the "best" drug is partly the one whose side effects you can live with, and a slower titration can make a stronger drug tolerable.
What about Ozempic and Mounjaro?
You'll notice Ozempic and Mounjaro aren't in the "approved for weight loss" column — that's because they're the diabetes-branded versions of the same molecules as Wegovy and Zepbound. They're frequently prescribed off-label for weight loss and contain identical active ingredients, but the FDA weight-management approval (and the dosing studied for it) belongs to Wegovy and Zepbound. For insurance and program purposes that distinction matters, even though the underlying drug is the same. Our medications comparison shows which brand maps to which use.
Who each one tends to suit
As a rough guide — always confirmed with a clinician: Zepbound appeals to people prioritising the largest average loss; Wegovy is a strong, well-studied middle option with broad recognition; Saxenda is a daily injection that may suit people who can't use the newer weekly drugs or whose coverage favours it. Because obesity is treated as a chronic condition, the best plan is usually the one you can stick with — see what happens if you stop.
The bottom line
If you want the single highest average number, tirzepatide (Zepbound) is the front-runner today. But the honest answer to "what's the best GLP-1 for weight loss?" is the one you can tolerate, afford and stay on — because most of the benefit comes from staying on a working dose over time. A drug that delivers 20% on paper but that you quit after two months over cost or side effects will lose to a "lesser" drug you actually keep taking.
So weigh the trial numbers alongside your coverage, your budget and how each one makes you feel, and make the call with a clinician rather than a leaderboard. Remember, too, that these figures are averages from tightly run trials with lifestyle support built in — your result depends on dose, starting point, diet, activity, sleep and biology, which is exactly why a "best for everyone" answer doesn't really exist. Treat the ranking as the start of a conversation, not a verdict.
A practical way to start that conversation: bring the trial numbers, your insurance details and an honest read on side effects to your clinician, and ask what they'd recommend for you given all three. You can also model an illustrative result for your own weight with our weight-loss calculator beforehand, so you walk in with realistic expectations rather than headline figures. And whatever you choose, give it time at a therapeutic dose before judging it — the early weeks on a low starter dose rarely reflect the final result.
Frequently asked questions
What is the best GLP-1 for weight loss?
By average trial loss, tirzepatide (Zepbound) ~20% leads, then semaglutide (Wegovy) ~15%, then liraglutide (Saxenda) ~5–8%. But 'best' also depends on tolerance, cost and coverage.
Is tirzepatide or semaglutide better for weight loss?
On average tirzepatide (Zepbound) produced more loss than semaglutide (Wegovy) in trials — but side effects, cost and your own response matter, so it's a clinician decision.
Which GLP-1 causes the most weight loss?
Tirzepatide (Zepbound) at higher doses has the largest average loss of the approved options — around 20% in trials.
Which GLP-1 is right for me?
That's for you and a clinician — based on your health, goals, tolerance and coverage. This is general education, not a recommendation.
Sources & further reading
- STEP trials (semaglutide 2.4 mg) and SURMOUNT trials (tirzepatide) — average weight-loss results.
- SCALE trials (liraglutide 3.0 mg).
- FDA prescribing information for Wegovy, Zepbound and Saxenda.