Wegovy is FDA-approved and considered safe for weight loss when used by people who meet the criteria, but it comes with a meaningful list of side effects and risks you should understand before starting. In clinical trials, nearly half of participants experienced nausea, and the drug carries a boxed warning related to thyroid tumors found in animal studies. For most eligible patients, the benefits outweigh the risks, but this is not a casual decision.
Who Wegovy Is Approved For
The FDA approved Wegovy for adults with obesity (a BMI of 30 or higher) or adults with overweight (a BMI of 27 to 29.9) who also have at least one weight-related health condition such as high blood pressure, high cholesterol, or type 2 diabetes. It’s also approved for adolescents aged 12 and older with obesity. In all cases, it’s meant to be used alongside a reduced-calorie diet and increased physical activity, not as a standalone fix.
If your BMI is below 27, or you’re in the 27 to 29.9 range without any related health conditions, Wegovy is not indicated for you. Using it off-label in those situations means the risk-benefit calculation hasn’t been formally evaluated.
How It Works in Your Body
Wegovy’s active ingredient mimics a natural gut hormone called GLP-1, which your body releases after eating. This hormone acts on several systems at once. It signals your brain to feel full sooner and stay satisfied longer. It slows the rate at which food leaves your stomach, so meals keep you feeling full for an extended period. And it promotes the release of other satiety-related hormones like leptin, which further suppresses appetite.
Because the drug crosses into the brain, it influences appetite regulation at a deeper level than simply making your stomach feel full. It adjusts the balance between hunger-promoting and satiety-promoting pathways in the brain, which is why people on Wegovy often describe a genuine reduction in food preoccupation rather than just willpower-assisted restraint.
How Much Weight People Actually Lose
In the major clinical trials, people taking the standard 2.4 mg weekly dose lost an average of about 15.6% of their body weight over roughly 68 to 72 weeks, compared to about 3.9% in the placebo group. For someone starting at 250 pounds, that translates to roughly 39 pounds lost over a year and a half. A newer, higher 7.2 mg dose showed even greater results, with participants losing an average of 18.7% of their body weight in the same timeframe.
These are averages. Some people lose considerably more, and some lose less. Individual response varies based on genetics, diet adherence, activity level, and how well you tolerate dose escalation.
Common Side Effects
Gastrointestinal problems are by far the most frequent side effects, and the numbers are high enough that you should expect some degree of stomach upset, especially in the early months as your dose increases:
- Nausea: 44% of trial participants (vs. 16% on placebo)
- Diarrhea: 30% (vs. 16% on placebo)
- Vomiting: 24% (vs. 6% on placebo)
- Constipation: 24% (vs. 11% on placebo)
For most people, these symptoms are mild to moderate and improve over time as the body adjusts. Wegovy is dosed gradually over 16 weeks, starting low and increasing monthly, specifically to reduce the severity of these effects. Still, in a two-year study, 82.2% of people on semaglutide experienced gastrointestinal side effects at some point during treatment, compared to 53.9% on placebo. That’s a high rate, even if most cases are manageable.
Serious Risks to Know About
Wegovy carries the FDA’s most prominent safety warning, a boxed warning, regarding thyroid tumors. In rodent studies, semaglutide caused thyroid C-cell tumors, including a type of thyroid cancer called medullary thyroid carcinoma. Whether this translates to humans remains uncertain. A recent study from the Mayo Clinic suggests the observed association in human data may reflect detection bias (more screening in people on the drug) rather than the medication actually causing cancer. Regardless, Wegovy is strictly contraindicated if you have a personal or family history of medullary thyroid carcinoma or a genetic condition called multiple endocrine neoplasia type 2.
Pancreatitis is another serious concern. If you develop severe, persistent abdominal pain that radiates to your back, especially with vomiting, that warrants urgent medical attention.
There have also been reports of gastroparesis, a condition where the stomach loses its ability to empty normally. In 2023, the FDA acknowledged receiving reports of gastroparesis with semaglutide, with some cases not resolving even after stopping the medication. However, no cases of gastroparesis appeared in the formal clinical trials, and the FDA has not confirmed that the drug directly causes the condition. The drug’s label does note that it slows gastric emptying, which is part of how it works, but severe, lasting stomach paralysis appears to be rare.
Wegovy is also contraindicated if you’ve ever had a serious allergic reaction to semaglutide or any of its inactive ingredients.
What Monitoring Looks Like During Treatment
Taking Wegovy responsibly means regular check-ins and blood work. In the first three months, your provider will typically check blood sugar markers, liver function, and kidney function. At six months, the monitoring usually expands to include a full cholesterol panel and thyroid function. By the one-year mark and annually after that, a broader metabolic workup is standard, including nutritional markers like vitamin D, B12, iron, and folate, since eating significantly less food over time can create deficiencies.
If you develop severe vomiting or diarrhea, kidney function should be checked promptly because dehydration from GI side effects can stress the kidneys. And if you have symptoms that could suggest pancreatitis, specific enzyme levels need to be tested urgently.
What Happens If You Stop Taking It
This is one of the most important things to understand before starting Wegovy: the weight tends to come back after you stop. A 2025 systematic review published in The BMJ found that people who stopped taking newer weight loss medications like semaglutide regained an average of about 0.8 kg (roughly 1.8 pounds) per month. That adds up to approximately 9.9 kg (about 22 pounds) regained within the first year after stopping.
More strikingly, the researchers projected that people would return to their original baseline weight within about 1.5 years of discontinuation. This doesn’t mean the medication failed. It means obesity is a chronic condition, and semaglutide works by continuously modifying appetite signals. When you remove the drug, those signals revert. For many people, this means Wegovy is a long-term or indefinite commitment, which has significant cost and planning implications.
The Bottom Line on Safety
For people who meet the BMI criteria, Wegovy has a well-studied safety profile and delivers meaningful weight loss that goes well beyond what diet and exercise alone typically achieve. The gastrointestinal side effects are common but usually tolerable. The serious risks, including the thyroid tumor warning and rare reports of gastroparesis, are real but affect a small fraction of users. The biggest practical concern for most people isn’t a dramatic adverse event but the reality that stopping the medication leads to substantial weight regain within one to two years, making this less of a short-term intervention and more of an ongoing treatment.