The newest weight loss drugs are injectable medications called GLP-1 receptor agonists, with Zepbound (tirzepatide) being the most recent FDA-approved option. Zepbound produced average weight loss of about 21% of body weight in clinical trials, making it the most effective prescription weight loss medication currently available. Its closest competitor, Wegovy (semaglutide), produces around 15% weight loss. Both are weekly injections, and a new generation of even more powerful drugs is already in late-stage testing.
How Zepbound and Wegovy Work
Both drugs mimic natural gut hormones that regulate appetite and blood sugar. When you eat, your body releases these hormones to signal fullness. The medications activate those same pathways at much higher levels, dramatically reducing hunger and slowing how quickly food leaves your stomach.
Wegovy targets one receptor: GLP-1. Zepbound targets two: GLP-1 and a second hormone receptor called GIP. That dual action is likely why Zepbound produces greater weight loss. In clinical trials, people taking the highest dose of Zepbound lost an average of 20.9% of their body weight over 72 weeks. Wegovy users lost an average of 14.9% over 68 weeks. For someone weighing 250 pounds, that’s roughly a 52-pound loss with Zepbound versus 37 pounds with Wegovy.
Benefits Beyond Weight Loss
These drugs do more than shrink waistlines. In the landmark SELECT trial, semaglutide (the active ingredient in Wegovy) reduced the risk of heart attack, stroke, or cardiovascular death by 20% in people with obesity and existing heart disease. That finding was significant enough that Wegovy became the first weight loss drug also approved for reducing cardiovascular risk. Researchers are studying tirzepatide for similar heart benefits, along with potential effects on sleep apnea, fatty liver disease, and kidney problems.
Common Side Effects
Nausea, vomiting, constipation, and diarrhea are the most frequent complaints, affecting up to 40% of people who take GLP-1 drugs. These side effects are usually worst in the first few weeks and tend to improve as your body adjusts. Still, more than 1 in 10 patients end up pausing or stopping treatment because of gastrointestinal symptoms.
To minimize these issues, both medications use a gradual dose increase. Wegovy starts at a low weekly dose and increases every four weeks over several months before reaching the full treatment dose. Zepbound follows a similar pattern, starting small and stepping up to 5, 10, or 15 milligrams depending on how you respond. This slow ramp-up gives your digestive system time to adapt, though some people still find the side effects difficult to tolerate.
What They Cost
Price has been one of the biggest barriers. Both manufacturers recently cut prices for people paying out of pocket. Wegovy dropped 23% to $499 per month. Zepbound’s starter dose fell to $349 per month, with higher doses also available at $499 through Eli Lilly’s self-pay program. These lower prices apply to uninsured patients and those whose insurance doesn’t cover weight loss medications.
Insurance coverage varies widely. Many employer plans and Medicare still don’t cover these drugs for weight loss specifically, though coverage is expanding as the cardiovascular benefits become better established. If your insurance does cover them, copays can range from modest to several hundred dollars depending on your plan.
What’s Coming Next
The next wave of weight loss drugs could make today’s options look modest. The most anticipated is retatrutide, an investigational drug from Eli Lilly that targets three hormone receptors instead of two. In its first successful Phase 3 trial, people taking retatrutide lost an average of 28.7% of their body weight over 68 weeks, translating to roughly 71 pounds. That would represent a significant leap beyond what Zepbound already achieves.
Another major shift is the move toward pills instead of injections. Oral amycretin, developed by Novo Nordisk (the maker of Wegovy), produced up to 13.1% weight loss after just 12 weeks in early clinical testing. That’s a striking result for such a short treatment period with a pill rather than a needle. If these oral options hold up in larger trials, they could make the drugs far more accessible to people who are uncomfortable with weekly injections or lack access to refrigerated storage.
What to Expect as a Patient
These medications are prescribed for adults with a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related health condition like high blood pressure, type 2 diabetes, or sleep apnea. You’ll typically start at the lowest dose, injecting once a week in your abdomen, thigh, or upper arm. Over the course of several months, your prescriber will gradually increase the dose based on how much weight you’re losing and how well you’re tolerating the medication.
Most people notice reduced appetite within the first few weeks, even at the starting dose. Food simply feels less urgent. Many describe losing interest in snacking or finding that smaller portions feel satisfying. The weight loss itself tends to be steady rather than dramatic at first, with the most significant changes appearing after three to six months at the full dose.
One important reality: these are long-term medications. Studies consistently show that people regain a significant portion of lost weight after stopping treatment. For most users, staying on the drug indefinitely is part of the plan, which makes cost and insurance coverage ongoing concerns rather than one-time hurdles.