The semaglutide shot is a once-weekly injectable medication that mimics a natural gut hormone to lower blood sugar, reduce appetite, and promote significant weight loss. It’s sold under two main brand names: Ozempic for type 2 diabetes and Wegovy for chronic weight management. In clinical trials, participants using the higher-dose version lost an average of 14.9% of their body weight over about 16 months.
How Semaglutide Works in Your Body
After you eat, your gut releases a hormone called GLP-1 that tells your pancreas to produce insulin, signals your liver to stop dumping extra sugar into your blood, and communicates with your brain that you’re full. The problem is that natural GLP-1 breaks down within minutes. Semaglutide is a synthetic version of this hormone, engineered to be 94% identical to the natural form but structured so it lasts an entire week in your body instead of disappearing in minutes.
The medication works on several fronts simultaneously. It boosts insulin release (only when blood sugar is elevated, which reduces the risk of dangerous blood sugar drops), suppresses the hormone glucagon that raises blood sugar, and slows how quickly food leaves your stomach. That slower gastric emptying means you feel full longer after meals. Semaglutide also suppresses ghrelin, your body’s hunger hormone, in a dose-dependent way, meaning higher doses produce stronger appetite suppression.
Ozempic vs. Wegovy: Same Drug, Different Purpose
Ozempic and Wegovy contain the same active ingredient but are approved for different conditions and come in different maximum doses.
Ozempic is FDA-approved for adults with type 2 diabetes. Its primary goals are improving blood sugar control alongside diet and exercise, reducing the risk of heart attack, stroke, or cardiovascular death in people with type 2 diabetes and heart disease, and slowing kidney disease progression in people with both type 2 diabetes and chronic kidney disease. The maximum weekly dose is 2 mg.
Wegovy is FDA-approved for chronic weight management in adults with a BMI of 30 or higher, or a BMI of 27 or higher with at least one weight-related condition like high blood pressure or high cholesterol. It’s also approved for children aged 12 and older with obesity. The injectable version maxes out at 2.4 mg per week, a higher ceiling than Ozempic, which accounts for its stronger weight loss results.
What the Clinical Trials Show
For weight loss, the landmark STEP trial published in the New England Journal of Medicine found that adults with obesity or overweight (plus at least one related health condition) lost an average of 14.9% of their body weight over 68 weeks on semaglutide 2.4 mg, compared to just 2.4% with a placebo. Both groups also followed a lifestyle program with diet and exercise, so that 14.9% reflects the drug’s added effect on top of those changes.
For blood sugar control, data pooled across four clinical trials showed that semaglutide significantly outperformed other diabetes medications. The higher dose (1 mg) reduced long-term blood sugar levels by an additional 0.38 to 1.07 percentage points compared to other treatments. That may sound small, but in diabetes management, reductions of that size meaningfully lower the risk of complications affecting the eyes, kidneys, and nerves.
How You Take the Shot
Semaglutide is injected once a week, on the same day each week, using a prefilled pen with a small needle that goes just under the skin. You can inject into three areas: your stomach, upper arm, or thigh. Rotating the injection site each week helps prevent irritation.
The dose starts low and increases gradually to minimize side effects. With Ozempic, you begin at 0.25 mg weekly for the first four weeks, then move up to 0.5 mg. From there, your dose may increase further depending on your response, up to the 2 mg maximum. Wegovy follows a similar escalation pattern, climbing over several months to its full 2.4 mg dose. You can take the shot with or without food, and if you need to shift your injection day, you just need at least two days between doses.
Common Side Effects
Gastrointestinal issues are the most frequent side effects, and they’re considerably more common than with a placebo. In clinical trials of the 2.4 mg dose, 44% of participants experienced nausea (versus 16% on placebo), 30% had diarrhea (versus 16%), 25% experienced vomiting (versus 6%), and 24% reported constipation (versus 11%).
These side effects tend to be worst during the dose-escalation phase, when your body is adjusting to each new level of medication. For most people, nausea and other GI symptoms become less frequent and less intense over time. Eating smaller meals, avoiding very fatty or rich foods, and staying hydrated can help during the adjustment period.
Serious Risks to Know About
Semaglutide carries an FDA boxed warning, the agency’s most serious safety label, based on animal studies that found an increased risk of thyroid C-cell tumors. These tumors have not been confirmed in humans at this point, but the warning means the medication is not recommended for anyone with a personal or family history of medullary thyroid carcinoma or a rare condition called Multiple Endocrine Neoplasia syndrome type 2.
Other serious but uncommon risks include pancreatitis (inflammation of the pancreas), gallbladder problems, and kidney issues, particularly in people who become dehydrated from vomiting or diarrhea. Low blood sugar is possible when semaglutide is combined with insulin or certain other diabetes medications, though it’s rare when used on its own because it only triggers insulin release when blood sugar is already elevated.
Compounded Versions and Safety Concerns
As demand for semaglutide has surged, compounding pharmacies have begun producing their own versions, often at lower prices. The FDA has raised specific concerns about these products. Some compounded versions use salt forms of semaglutide, such as semaglutide sodium or semaglutide acetate, which are chemically different active ingredients from what’s in the approved drugs. The FDA has stated it does not have information on whether these salt forms share the same properties as the original, and it is not aware of any lawful basis for their use in compounding. If you’re considering a compounded version, the key distinction is that these products have not gone through the same testing for safety, potency, or sterility as the branded medications.