Ozempic is a once-weekly injection that mimics a natural gut hormone to lower blood sugar, reduce appetite, and promote weight loss. It contains semaglutide, a lab-made version of a hormone your body already produces called GLP-1. This hormone plays a central role in how your body processes food, and Ozempic amplifies its effects far beyond what your body can do on its own.
How Ozempic Works in Your Body
After you eat, your gut releases GLP-1 to signal your pancreas to produce insulin. Natural GLP-1 breaks down in minutes. Semaglutide is engineered to last about a week, which is why you only inject it once every seven days. While it’s active, it triggers three key effects: it tells your pancreas to release more insulin when blood sugar is high, it dials back glucagon (a hormone that raises blood sugar), and it slows down how fast food leaves your stomach.
That slowdown in stomach emptying is a big part of why people feel full longer after meals. In one study, patients taking semaglutide were nearly five times more likely to still have solid food in their stomachs during a medical procedure compared to patients not on the drug. This delayed digestion blunts the blood sugar spikes that typically follow a meal, which is especially useful for people with type 2 diabetes.
What It Does to Appetite and Cravings
Ozempic doesn’t just work in your gut. It crosses into your brain and affects neurons in the hypothalamus that control hunger. Specifically, it suppresses a group of neurons called AgRP neurons, which normally fire up when you’re losing weight to tell your brain “you need to eat.” Semaglutide quiets those signals while simultaneously activating brainstem neurons that promote a feeling of fullness. The result is a two-pronged effect: you feel satisfied sooner during meals, and your brain doesn’t ramp up hunger signals to compensate for eating less.
Many people describe this as a reduction in “food noise,” the constant background thinking about what to eat next. It’s not that food becomes unappealing. Rather, the mental preoccupation with eating fades.
Blood Sugar Control
Ozempic is FDA-approved for type 2 diabetes, and its blood sugar lowering effects are substantial. Across the SUSTAIN clinical trial program, a 1 mg weekly dose reduced HbA1c (a measure of average blood sugar over roughly three months) by 1.5% to 1.8% after 30 to 56 weeks of treatment. For context, most diabetes medications aim for a reduction of about 1%, so semaglutide outperforms many alternatives.
The starting dose of 0.25 mg isn’t actually strong enough to control blood sugar on its own. It exists purely to let your body adjust to the medication and minimize side effects. After four weeks, the dose increases to 0.5 mg, and if more blood sugar control is needed after at least another four weeks, it can go up to 1 mg, which is the maximum approved dose for diabetes.
Weight Loss Effects
Weight loss is one of the most talked-about effects of semaglutide, even though Ozempic is technically approved for diabetes rather than weight management. (Its higher-dose sibling, Wegovy, carries the weight loss approval.) In clinical trials, participants taking 2.4 mg of semaglutide weekly alongside lifestyle changes lost an average of 14.9% of their body weight over 68 weeks, compared to just 2.4% in the placebo group.
The numbers break down further in a way that’s useful to set expectations. About 86% of participants on semaglutide lost at least 5% of their body weight. Roughly 69% lost 10% or more. And about half, 50.5%, lost 15% or more. In the placebo group, fewer than 5% hit that 15% threshold. These results came with structured lifestyle changes including diet and exercise, so the drug works best as part of a broader effort rather than as a standalone fix.
Cardiovascular Benefits
Beyond blood sugar and weight, semaglutide appears to protect the heart. In the SELECT trial, which studied patients with obesity and existing cardiovascular disease (but not diabetes), semaglutide reduced the risk of major cardiovascular events like heart attack, stroke, and cardiovascular death by 20%. This is a meaningful reduction and one of the reasons the drug has drawn attention beyond the diabetes community. The cardiovascular benefit appears connected to, but not entirely explained by, the weight loss itself.
Common Side Effects
The most frequent side effects are gastrointestinal: nausea, vomiting, diarrhea, abdominal pain, and constipation. These affect at least 5% of users. In trials comparing the 1 mg and 2 mg doses, about 31% of people on the lower dose and 34% on the higher dose experienced GI symptoms. Most of these are mild to moderate and tend to ease as the body adjusts over the first few weeks, which is exactly why the dose starts low and ramps up gradually.
A small percentage of people find the side effects intolerable. In placebo-controlled trials, about 3% to 4% of patients on Ozempic discontinued due to GI problems, compared to less than 1% on placebo. Severe gastrointestinal reactions were rare, occurring in under 1% of participants.
Ozempic also carries an FDA boxed warning related to thyroid tumors. In animal studies, semaglutide caused thyroid C-cell tumors in rodents. It’s unknown whether this translates to humans, but the drug is contraindicated for anyone with a personal or family history of medullary thyroid carcinoma or a condition called Multiple Endocrine Neoplasia syndrome type 2.
How the Injection Works
Ozempic comes in a prefilled pen that you inject under the skin of your abdomen, thigh, or upper arm once a week, on the same day each week. The pen has a small, thin needle, and most people describe the injection as a brief pinch. You don’t need to inject it at a specific time of day or coordinate it with meals.
The standard titration schedule spans at least eight weeks. You start at 0.25 mg weekly for four weeks, then move to 0.5 mg. If your doctor decides you need more blood sugar control, the dose can increase to 1 mg after at least four more weeks at 0.5 mg.
Storing Your Ozempic Pen
Before first use, keep the pen refrigerated between 36°F and 46°F. It stays good until the expiration date printed on it. Once you’ve used it for the first time, the pen lasts 56 days whether you keep it refrigerated or store it at room temperature (up to 86°F). If the pen has ever been exposed to temperatures below 36°F or above 86°F, it should be discarded. Don’t freeze it, and keep the pen cap on when you’re not using it to protect it from light.