The hormone it copies
When you eat, your gut releases GLP-1. It tells your pancreas to release insulin when blood sugar is high, slows how fast food leaves your stomach, and signals fullness to your brain. Natural GLP-1 breaks down within minutes. Semaglutide, the medicine in Ozempic, is built to last about a week, so one shot covers seven days. Watch it in 20 seconds in our GLP-1 explainer.
Why that leads to weight loss
- You feel full sooner and longer because your stomach empties more slowly.
- Hunger and food thoughts quiet down through appetite centers in the brain.
- You naturally eat less, which creates a calorie deficit without counting every bite. See what that means for your numbers with TDEE on a GLP-1.
Explainer · 0:23
Read the transcript
- After you eat, your gut releases a hormone called GLP-1. GLP-1 medicines copy it, but last much longer in the body.
- It slows how fast your stomach empties, so you feel full sooner and stay full for longer.
- It also acts on appetite centers in the brain, which quiets hunger and constant thoughts about food.
- When blood sugar is high, it helps the pancreas release insulin. Tirzepatide also acts on a second gut hormone, GIP.
Ozempic vs Wegovy
| Ozempic | Wegovy | |
|---|---|---|
| Medicine | semaglutide | semaglutide |
| Approved for | Type 2 diabetes, heart and kidney protection in type 2 diabetes | Weight management, heart-risk reduction |
| Highest dose | 2 mg weekly | 2.4 mg weekly |
| Weight result | Modest loss in diabetes trials | 14.9% average in STEP 1 |
Full comparison: Ozempic vs Wegovy.
Its effect on blood sugar
Semaglutide also helps the pancreas release insulin when blood sugar is high, and lowers glucagon, a hormone that raises blood sugar. Because the insulin boost depends on blood sugar being high, semaglutide on its own rarely causes low blood sugar. The risk goes up when it's combined with insulin or a sulfonylurea. That's why Ozempic was built as a diabetes medicine first, and why weight loss showed up as a side benefit.
What to expect early on
On the Ozempic label, doses start at 0.25 mg weekly for 4 weeks, then move to 0.5 mg. The prescriber may raise it to 1 mg and then 2 mg, at least 4 weeks apart, if more blood sugar control is needed. The 0.25 mg start is there to help your stomach adjust; it isn't meant to control blood sugar. See the Ozempic dosage page for the label details.
Stomach side effects like nausea are most common during those increases and usually ease on the same dose. Tips that help: smaller meals, stopping when you're full, and going easy on greasy food. See nausea on GLP-1s.
How long it takes to work
| Time | What often happens |
|---|---|
| First 1 to 2 weeks | Some people notice smaller appetite and fuller feelings soon after starting |
| Weeks 4 to 5 on a dose | Medicine levels settle, since semaglutide lasts about a week in the body |
| First few months | Weight loss builds slowly as the dose steps up |
| About a year | In Wegovy's STEP 1 trial, weight kept falling for more than a year before leveling off |
Everyone is different, and the scale won't move in a straight line. Track the trend, not single days, with the weigh-in tracker.
Why results vary from person to person
- Dose. Higher doses produced more loss in trials. Wegovy goes up to 2.4 mg; Ozempic tops out at 2 mg.
- Diabetes. People with type 2 diabetes tend to lose less. In STEP 2, adults with type 2 diabetes on semaglutide 2.4 mg lost 9.6% on average, compared with 14.9% in STEP 1 for people without diabetes.
- Habits. What you eat on a smaller appetite still matters. Protein helps protect muscle: find your protein floor.
- Biology. Some people respond strongly and some don't, for reasons researchers are still studying.
Common mistakes in the first months
- Eating too little. A quiet appetite can make it easy to skip meals. Aim for regular small meals with protein, and don't drop below about 1,200 calories a day for women or 1,500 for men unless a clinician is supervising you. The TDEE on a GLP-1 tool helps set a sensible target.
- Forgetting fluids. Less food often means less water, and nausea makes it worse.
- Pushing through big meals. Eating past fullness is a common trigger for nausea and vomiting.
- Expecting the scale to drop every week. Plateaus are normal and don't mean it stopped working.
When to talk to your doctor
- If you're thinking about semaglutide for weight: ask whether Wegovy is the right version for you.
- If you have severe stomach pain that won't go away, with or without vomiting.
- If you notice a lump in your neck or trouble swallowing.
- If you take insulin or a sulfonylurea, because low blood sugar risk rises.
Run your numbers
Keep reading
Common questions
How does Ozempic make you lose weight?
It mimics GLP-1, a fullness hormone, so you feel full sooner and hungry less often, and you naturally eat less.
How fast does Ozempic work for weight loss?
Appetite often changes in the first weeks, but weight loss builds over months as the dose steps up. In Wegovy's trial, loss continued for more than a year.
Is Ozempic the same as Wegovy?
Same medicine, semaglutide, but different approvals and doses. Wegovy is approved for weight management.
Sources
Clinician review pending. Drafted from primary sources and waiting for sign-off by a licensed clinician (MD, DO or PharmD) before launch. Every number is checked against its source. Drug facts are re-checked quarterly, prices monthly and whenever a label changes. How we review · Report an error