Wegovy weight loss injections work by delivering semaglutide, a GLP-1 receptor agonist that mimics a natural gut hormone your body releases after eating. The shot binds to and activates GLP-1 receptors in areas of the brain that control appetite, which reduces hunger and how much you eat, and it slows how quickly the stomach empties so you feel full for longer. Given once a week under the skin alongside a reduced-calorie diet and more physical activity, Wegovy produced average weight loss of about 15 percent in its main clinical trials.
What follows covers how the Wegovy injection works in the brain and body, what it is approved for, how the dose is built up over time, what the trials showed, and what happens if you stop. Wegovy is prescription-only, individual results vary, and any decision to start should be made with a licensed healthcare provider.
Semaglutide, the active ingredient in Wegovy, shares 94 percent of its structure with the human hormone GLP-1. It has been modified to resist the enzyme that normally breaks GLP-1 down within a minute or two, which extends its action to roughly five to seven days and is why it only needs to be injected once a week.
The weight loss effect comes from several connected pathways. The main one is central appetite suppression: GLP-1 receptors are found throughout the hypothalamus and brainstem, and semaglutide activates the appetite-reducing POMC neurons in the brain while quieting the hunger-promoting circuits. In one clinical study, semaglutide 2.4 mg cut the amount eaten at an unrestricted lunch by 35 percent compared with placebo. The injection also slows gastric emptying through the vagus nerve, which prolongs the feeling of fullness, and it acts on the brain's reward system to reduce the pull of highly palatable food.
On the metabolic side, semaglutide increases insulin release when blood sugar is high, lowers glucagon, and improves how the body handles fats. Most of the weight that comes off is fat rather than muscle. Animal studies show the medication reaches and activates the specific brain regions that regulate food intake, which helps explain why the effect on appetite is so consistent.
The FDA has approved Wegovy, used together with a reduced-calorie diet and increased physical activity, for several uses:
Wegovy also comes in an oral tablet form, but the once-weekly injection is the original and most widely used version, and it is the focus here. Whether any of these uses applies to you is a medical decision that requires evaluation by a provider.
The Wegovy injection is started low and increased gradually, which gives the body time to adjust and helps limit side effects like nausea. The starting dose is not meant to drive weight loss on its own; it is a ramp-up. The standard schedule looks like this:
| Phase | Dose (once weekly) | Notes |
| Weeks 1 to 4 | 0.25 mg | Starting dose; not for weight loss, helps the body adjust |
| Weeks 5 to 8 | 0.5 mg | First step up |
| Weeks 9 to 12 | 1 mg | Second step up |
| Weeks 13 to 16 | 1.7 mg | Third step up |
| Week 17 onward | 2.4 mg | Recommended maintenance dose |
| If more loss is needed | Up to 7.2 mg | Only after tolerating 2.4 mg for 4+ weeks, per the label |
If a dose is not well tolerated during the build-up, the next increase can be delayed by four weeks rather than pushed through. The recommended maintenance dose is 2.4 mg once weekly. For people who tolerate 2.4 mg for at least four weeks and need additional weight reduction, the label now allows an increase up to a maximum of 7.2 mg once weekly. The right dose and pace are set by your provider based on how you respond and tolerate the medication.
In practice, the injection is given on the same day each week and can be taken at any time of day, with or without food, into the abdomen, thigh, or upper arm. The pen is designed for self-injection at home, and the injection site can be rotated to reduce irritation. If you miss a dose and the next scheduled dose is more than two days away, the label allows taking it as soon as you remember; otherwise it is skipped. The most common side effects across the dosing schedule are gastrointestinal, mainly nausea, diarrhea, vomiting, and constipation, and they are usually mild to moderate and tend to settle as the body adjusts to each step up. Less common but important risks include gallbladder problems and pancreatitis, so any persistent or severe abdominal pain should be reported to a provider promptly.
The STEP trial program established Wegovy's weight loss results, and these are clinical trial averages rather than promises, since individual responses vary.
In the STEP 1 trial, about a third of participants lost at least 20 percent of their starting weight. As the trial investigators noted, that degree of reduction approaches what is reported one to three years after some bariatric surgery, though Wegovy is a medication rather than a procedure and is not a substitute for surgical care when that is indicated. Results were achieved alongside diet and activity changes, and they vary from person to person.
Wegovy's benefits go beyond weight. In the STEP trials, semaglutide improved several cardiometabolic markers, including a roughly 14 cm reduction in waist circumference, about a 6 mmHg drop in systolic blood pressure, and improvements in HbA1c and lipids.
The strongest cardiovascular evidence comes from the SELECT trial, which followed 17,604 adults with established cardiovascular disease and a BMI of 27 or higher who did not have type 2 diabetes. In that trial, Wegovy 2.4 mg reduced major adverse cardiovascular events, the combined risk of cardiovascular death, heart attack, and stroke, by 20 percent compared with placebo. This makes semaglutide the basis for Wegovy's approval to reduce cardiovascular risk in that specific population. As with all of these findings, the benefit applies to the group studied and does not guarantee an individual outcome.
Obesity is a chronic condition, and the evidence suggests Wegovy may need to be used long term. In a follow-up of participants for an additional 52 weeks after they completed 68 weeks of treatment, people regained, on average, a substantial share of the weight they had lost, with a mean regain of about 11.6 percent of body weight. Cardiometabolic improvements tended to fade in parallel.
For this reason, patients should be counseled that anti-obesity medications may need to be continued long term to sustain the benefits. Stopping is a decision to make with your provider, who can help plan a maintenance approach. This pattern is not unique to Wegovy; weight regain after stopping is seen across this class of medications and reflects the underlying biology of obesity rather than a failure of willpower. For most people this is a long-term treatment rather than a short course, which is worth weighing before you start.
How does the Wegovy injection work for weight loss?
Wegovy contains semaglutide, which activates GLP-1 receptors in the brain to reduce appetite and slow stomach emptying, so you feel full sooner and eat less. It is used alongside a reduced-calorie diet and more physical activity.
How often do you take Wegovy?
The injection is given once a week, on the same day each week, under the skin of the abdomen, thigh, or upper arm. The dose is increased gradually over several months to a maintenance dose of 2.4 mg.
How much weight do people lose on Wegovy?
In the STEP 1 trial, adults without diabetes lost an average of about 15 percent of body weight over 68 weeks, with roughly a third losing at least 20 percent. These are averages, and individual results vary.
What are the common side effects of Wegovy?
The most common side effects are gastrointestinal, including nausea, vomiting, diarrhea, and constipation, and they tend to ease with slow dose increases. Wegovy carries a boxed warning about thyroid C-cell tumors and is not for people with a personal or family history of medullary thyroid carcinoma or MEN2. Talk to a healthcare provider about your risks.
Do you regain weight after stopping Wegovy?
Yes, weight regain is common after stopping, which is why it is generally considered a long-term medication. Your provider can help you plan how to maintain results.
Learn more: FDD Weight Loss Program | Eligibility quiz
