The most well-known weight loss injection is called Wegovy, which is the brand name for semaglutide. It was approved by the FDA in 2021 for chronic weight management and has since become the most widely discussed obesity medication in the world. But Wegovy isn’t the only option. A second injection called Zepbound (brand name for tirzepatide) was approved more recently, and an older daily injection called Saxenda (liraglutide) is also still available. All three work in similar ways, though they differ in how often you take them, how much weight people typically lose, and what they cost.
The Three Main Weight Loss Injections
Wegovy (semaglutide) is a once-weekly injection approved for adults and children aged 12 and older with a BMI of 30 or above, or a BMI of 27 or above with at least one weight-related health condition like high blood pressure or type 2 diabetes. You start at a low dose and increase every four weeks over several months, eventually reaching a maintenance dose. A newer, higher maintenance dose is also available for people who need additional weight reduction.
Zepbound (tirzepatide) is also a once-weekly injection, approved for adults with a BMI of 30 or greater, or 27 or greater with a weight-related condition. What sets Zepbound apart is that it targets two gut hormones instead of one, which may account for the somewhat greater weight loss seen in clinical trials.
Saxenda (liraglutide) is the oldest of the three and requires a daily injection rather than a weekly one. It works through the same basic mechanism as Wegovy but is generally associated with more modest weight loss. It remains an option for people who don’t tolerate the newer medications.
A fourth injection, Imcivree (setmelanotide), exists but works through an entirely different pathway and is only prescribed for people with specific rare genetic conditions that cause obesity. Most people searching for “the weight loss injection” are looking for one of the first three.
How These Injections Work
Wegovy, Zepbound, and Saxenda all mimic a natural hormone your small intestine produces after you eat. This hormone does three things at once: it signals your pancreas to release insulin (which lowers blood sugar), it blocks a second hormone that would otherwise raise blood sugar, and it slows how quickly your stomach empties food into your digestive tract. That slower emptying is a big part of why people feel full sooner and stay satisfied longer between meals.
The net effect is a significant reduction in appetite and hunger. People on these medications often describe food as simply being less interesting, or feeling satisfied after eating far less than they used to. Zepbound takes this a step further by also mimicking a second gut hormone called GIP, which appears to amplify the appetite-suppressing and blood-sugar-lowering effects.
Common Side Effects
The most frequent side effects are digestive. Nausea, diarrhea, constipation, stomach discomfort, and acid reflux are all common, especially during the first few weeks or after each dose increase. Vomiting and bloating also occur in some people. These effects tend to be worst early on and improve as your body adjusts, which is why the dosing schedule starts low and increases gradually over months.
More serious but less common risks include acute pancreatitis (sudden, severe inflammation of the pancreas), gallbladder disease, and kidney injury. All three medications also carry an FDA boxed warning about a potential risk of a rare type of thyroid tumor called medullary thyroid carcinoma. This risk has been observed in animal studies, and the injections are not prescribed to anyone with a personal or family history of this cancer. If you notice a lump in your neck, difficulty swallowing, or persistent hoarseness while on one of these medications, that warrants prompt medical attention.
Who Qualifies for a Prescription
The general FDA criteria are straightforward: you need a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related medical condition such as high blood pressure, type 2 diabetes, or high cholesterol. These medications are meant to be used alongside diet and exercise, not as a replacement for them. For Wegovy specifically, adolescents aged 12 and older with obesity are also eligible.
Your doctor will evaluate whether the benefits outweigh the risks for your situation. People with a history of pancreatitis, certain thyroid cancers, or severe allergic reactions to the medication’s ingredients would not be candidates.
What They Cost
The list price for Wegovy is roughly $1,350 for a 28-day supply, which works out to about $16,200 per year. Zepbound and Saxenda fall in a similar range. These are among the most expensive medications people commonly search for, and the out-of-pocket cost depends entirely on your insurance.
Private insurance coverage varies widely. Some plans cover weight loss injections with prior authorization, others exclude them entirely, and some cover them only for diabetes (under different brand names like Ozempic or Mounjaro) but not for weight management. Medicare has historically not covered anti-obesity medications at all, but a new program called the Medicare GLP-1 Bridge is set to begin in July 2026. It will provide coverage for Wegovy and Zepbound for eligible Medicare beneficiaries who meet specific clinical criteria, including a BMI of 35 or above, or a BMI of 30 or above with conditions like uncontrolled high blood pressure, heart failure, or chronic kidney disease.
How the Injections Are Taken
Wegovy and Zepbound are both once-weekly self-injections using a prefilled pen. You inject just under the skin of your abdomen, thigh, or upper arm, rotating the site each week. The pen comes preloaded with the correct dose, so there’s no measuring involved. Most people find the process quick and relatively painless once they get used to it.
The dose ramps up gradually. With Wegovy, you start at the lowest dose and increase every four weeks over about 16 to 20 weeks before reaching the maintenance level. This slow escalation is designed to minimize nausea and give your body time to adjust. Zepbound follows a similar pattern. Saxenda also starts low and increases, but because it’s a daily injection, the escalation moves at a different pace.
These medications are intended for long-term use. Studies consistently show that people regain weight after stopping, which is why they’re classified as chronic weight management treatments rather than short-term interventions. A newer oral tablet form of semaglutide (also under the Wegovy brand) has recently become available as well, offering a daily pill option for people who prefer not to inject.