Which GLP 1 is best for weight loss?

Tirzepatide produces most weight loss of any GLP 1 drug on market right now. In first head to head trial comparing tirzepatide directly against semaglutide in people with obesity, participants on tirzepatide lost an average of 20.2% of their body weight over 72 weeks, compared to 13.7% for semaglutide. That trial, called SURMOUNT 5, was published in New England Journal of Medicine in May 2025 and enrolled 751 adults without diabetes.

But "best" is a complicated word. Tirzepatide puts up bigger numbers on paper. It does not mean it is right choice for every person. Your insurance, your medical history, how you handle side effects, and whether you prefer a daily pill or a weekly injection all matter. Let's walk through each drug so you can see full picture.

How does tirzepatide compare to semaglutide?

Tirzepatide works on two receptors. It activates both GLP 1 and GIP (glucose dependent insulinotropic polypeptide). Semaglutide only activates GLP 1. That dual mechanism is main reason tirzepatide produces more weight loss.

In SURMOUNT 5 trial, both drugs were pushed to their maximum tolerated doses. Tirzepatide could go up to 15 mg and semaglutide up to 2.4 mg. At those doses, tirzepatide beat semaglutide on every weight related endpoint. About 32% of tirzepatide patients lost 25% or more of their body weight. Only 16% of semaglutide patients reached that same mark.

The side effect profiles were similar. Both drugs caused nausea, diarrhea, and constipation at comparable rates. Tirzepatide had slightly more injection site reactions, but they were mild. Serious adverse events were rare in both groups.

So if weight loss alone is deciding factor, tirzepatide comes out ahead based on this trial. But there are reasons a doctor might still recommend semaglutide for a specific patient.

What about other GLP 1 drugs?

Not every GLP-1 drug is approved for weight loss. Some are approved for type 2 diabetes and cause weight loss as a secondary benefit. Here is how they stack up.

Semaglutide 2.4 mg (Wegovy) is most studied GLP 1 specifically for obesity in people without diabetes. In STEP 1 trial, it produced an average loss of 14.9% of body weight at 68 weeks. It has FDA approval for chronic weight management.

Semaglutide 1.0 mg (Ozempic) is approved for type 2 diabetes, not for weight loss. But it is frequently prescribed off label at lower doses for people who want to lose weight. The weight loss is less than what you see with 2.4 mg dose.

Tirzepatide is sold under two brand names. Mounjaro is approved for type 2 diabetes. Zepbound is approved for obesity. Same drug, different indication and dose range.

Liraglutide 3.0 mg (Saxenda) was first GLP 1 approved for weight management. It is a daily injection. Average weight loss in trials was around 5% to 8% of body weight. That is less than half of what semaglutide and tirzepatide achieve. Saxenda is still available, and some people prefer it because of its lower cost or because a daily injection feels easier to manage than a weekly one. But in terms of results, it trails behind newer drugs. If you're weighing Saxenda against newer options, our Saxenda vs Zepbound comparison goes deeper into those differences.

Dulaglutide (Trulicity) is a weekly injection approved for type 2 diabetes. It produces modest weight loss, roughly 2 to 4 kg more than placebo. It is not prescribed primarily for weight management. If you are curious about how it stacks up against Ozempic for diabetes, we cover that in Trulicity vs Ozempic.

Exenatide (Byetta and Bydureon) was first GLP-1 drug approved back in 2005. It produces less weight loss than semaglutide or tirzepatide and is rarely first choice for weight management today.

Why might semaglutide still be better choice for some people?

Semaglutide has more long term safety data than tirzepatide. It has been on market longer. The SELECT trial demonstrated that semaglutide reduces risk of major cardiovascular events like heart attacks and strokes in people with obesity. Tirzepatide does not have that cardiovascular outcome data yet. There are trials underway, but results aren't available.

If you have obesity and a history of cardiovascular disease, your doctor might lean toward semaglutide specifically because of that proven heart benefit.

Insurance is another factor. Some plans cover Wegovy but not Zepbound, or other way around. Some cover neither. The out of pocket cost for these drugs without insurance runs over $1,000 per month. Which drug your plan covers may override which drug produces a few more percentage points of weight loss.

Availability matters too. Both semaglutide and tirzepatide have experienced supply shortages since they became popular. Depending on where you live and when you fill your prescription, one drug may simply be easier to get than other.

Does it matter whether you have diabetes?

Yes. People with type 2 diabetes generally lose less weight on GLP 1 drugs than people without diabetes. In STEP 2 trial, people with diabetes on semaglutide 2.4 mg lost about 9.6% of their body weight, compared to 14.9% in STEP 1 trial in non diabetic participants.

The reason is that diabetes changes metabolism. Insulin resistance, higher baseline insulin levels, and effects of other diabetes medications all influence how much weight a GLP 1 drug can push off.

If you have type 2 diabetes, both tirzepatide and semaglutide are strong options because they lower blood sugar and promote weight loss at same time. Tirzepatide showed slightly better blood sugar control than semaglutide in SURPASS-2 trial, which compared them head to head in people with diabetes.

So which one should you pick?

Here is a practical way to think about it.

If your main goal is maximum weight loss and you don't have cardiovascular disease, tirzepatide at highest tolerable dose currently produces best results. The data from SURMOUNT 5 is clear on that.

If you have obesity and a history of heart disease, semaglutide has cardiovascular outcome data that tirzepatide doesn't yet. That matters if reducing your risk of a heart attack or stroke is part of treatment plan.

If cost or insurance is a concern, drug your plan covers is best drug for you. A 14% weight loss on a covered drug beats a 20% weight loss on a drug you can't afford to take consistently.

If you prefer a daily injection over a weekly one, liraglutide (Saxenda) is an option, though weight loss will be more modest.

There is no single best GLP 1 for everyone. But for most people without diabetes who want most weight loss and can access either drug, tirzepatide is stronger performer based on everything we have right now.

Your doctor can look at your full medical picture and help you decide. That conversation is real starting point.