If you’re trying to figure out why your friend, your cousin, and your coworker are all on what sounds like the same medication but with four different names, here’s what’s actually going on.

Two drugs, four names

There are really only two medications in this conversation. The four brand names are about marketing and FDA approvals, not chemistry.

• Semaglutide is sold as Ozempic (for type 2 diabetes) and Wegovy (for weight loss). Same drug, made by Novo Nordisk.
• Tirzepatide is sold as Mounjaro (for type 2 diabetes) and Zepbound (for weight loss). Same drug, made by Eli Lilly.

Why two names for the same molecule? Mostly because the FDA approves drugs for specific uses, and the labeled doses differ between the diabetes and weight-loss versions. Wegovy goes up to a higher dose than Ozempic. Zepbound and Mounjaro top out at the same dose, but the packaging, the patient instructions, and crucially the insurance coverage are different. Insurance is the real reason your doctor cares which one is on your prescription.

How they actually work

Both work by mimicking gut hormones that show up after you eat. The hormones tell your brain you’re full, slow down how fast your stomach empties, and nudge your pancreas to release insulin when blood sugar rises. The result: less appetite, smaller portions feel satisfying, and blood sugar stays steadier.

The difference is how many of those hormones each drug imitates. Semaglutide hits one receptor (GLP-1). Tirzepatide hits two (GLP-1 and GIP). That extra hormone is the reason most people lose more weight on tirzepatide than on semaglutide.

Which one loses more weight?

Tirzepatide. It’s not particularly close. A 2025 head-to-head trial called SURMOUNT-5 compared the two directly over 72 weeks: people on tirzepatide lost about 20% of their body weight, people on semaglutide lost about 14%. For a 200-pound starting weight, that’s roughly 40 pounds vs 27.

That doesn’t mean tirzepatide is automatically the right choice. Semaglutide has a longer track record (it’s been around longer), it’s been studied in more populations, and it has cardiovascular outcome data — the SELECT trial showed it reduces heart attacks and strokes in people with cardiovascular disease and obesity. Tirzepatide is also approved for obstructive sleep apnea in adults with obesity, which semaglutide isn’t.

Side effects: pretty similar across all four

The most common side effects are GI: nausea, constipation, diarrhea, occasional vomiting. They tend to peak in the first few weeks of each dose increase, then settle. Most people manage them with smaller meals, eating more slowly, and stopping before they’re fully full. About 5 to 10% of people stop because of GI issues they can’t get past.

The bigger-deal side effects are rarer but worth knowing about: pancreatitis (severe ongoing belly pain that radiates to the back), gallbladder problems, and a thyroid warning that means these drugs aren’t for people with a personal or family history of medullary thyroid cancer. None of these is common, but they’re the reasons your doctor will ask about your family history before prescribing.

One thing that’s come up more recently: if you’re going under anesthesia for a procedure, you’ll likely be told to skip your weekly dose for at least a week beforehand. The slowed stomach emptying can make sedation riskier.

Cost is the other big difference

List prices for all four are around $1,000 to $1,400 per month. Insurance coverage varies dramatically — many plans cover the diabetes versions (Ozempic, Mounjaro) but won’t touch the weight-loss versions (Wegovy, Zepbound) without significant prior authorization. Manufacturer savings programs help meaningfully when you qualify. Compounded versions from compounding pharmacies are sometimes cheaper but are not FDA-approved and have had issues with dosing accuracy and quality control — the FDA has warned about them.

For more on what these medications do, when they’re a fit, and the lifestyle changes that make them work better, see our deeper guide on weight-management medications. If you want transparent cash pricing on a specific medication, you can check our semaglutide page directly.

The honest bottom line

These medications work. They also cost a lot, have real side effects, and tend to be a long-term commitment — most people regain most of the weight when they stop. Tirzepatide produces more weight loss than semaglutide on average. The “right” choice depends on whether you have diabetes, what your insurance covers, what side effects you can tolerate, and whether you and your prescriber think the long-term math makes sense for your situation.

If you’re trying to work out which one is for you, that’s the conversation to have — not whether one of these is “better” in the abstract.