Ozempic Side Effects: What to Expect, How Long They Last and How to Track Them
The most common Ozempic side effects are nausea, diarrhea, vomiting and constipation, and for most people they're mild to moderate and settle within weeks as the body adjusts to each dose. Ozempic contains semaglutide, and in weight-loss trials of semaglutide 2.4 mg, 44% of adults had nausea, mostly while the dose was going up, and more than 9 in 10 stayed on treatment (Wegovy prescribing information). Most of it is part of the adjustment, not a sign anything is wrong. Glapp, the Ozempic dose tracker, lets you log every side effect right next to your Ozempic doses, so you can see your pattern and watch it ease.
Key numbers
| Number | What it means |
|---|---|
| 44% | of adults on semaglutide 2.4 mg had nausea in weight-loss trials, the most common side effect, vs 16% on placebo |
| 17,836 | users currently tracking Ozempic side effects in Glapp |
| 73% | had at least one stomach side effect, vs 47% on placebo, mostly during dose increases |
Ozempic side effects: what the clinical trials show
Ozempic and Wegovy are two brands of the same molecule, semaglutide, both made by Novo Nordisk. Wegovy is the one approved for weight loss and goes up to 2.4 mg; Ozempic's doses go up to 2 mg. That makes Wegovy's weight-loss trials the closest evidence for anyone using Ozempic to lose weight. Across those trials (1,261 adults on placebo, 2,116 on semaglutide 2.4 mg):
| Side effect | Placebo | Semaglutide 2.4 mg |
|---|---|---|
| Nausea | 16% | 44% |
| Diarrhea | 16% | 30% |
| Vomiting | 6% | 24% |
| Constipation | 11% | 24% |
| Abdominal pain | 10% | 20% |
| Headache | 10% | 14% |
| Fatigue | 5% | 11% |
| Indigestion (dyspepsia) | 3% | 9% |
| Dizziness | 4% | 8% |
| Bloating (abdominal distension) | 5% | 7% |
| Burping (eructation) | <1% | 7% |
| Gas (flatulence) | 4% | 6% |
| Acid reflux (GERD) | 3% | 5% |
| Hair loss | 1% | 3% |
Source: Wegovy prescribing information, Table 3. Rates are at 2.4 mg, a little above Ozempic's highest dose, so they may run slightly higher than what you see on Ozempic.
Severe stomach side effects were uncommon: 4.1% vs 0.9% on placebo. In STEP 1 (1,961 adults, 68 weeks), people on semaglutide 2.4 mg lost 14.9% of their body weight vs 2.4% on placebo, and stomach side effects were mostly mild to moderate and temporary.
Common Ozempic side effects, one by one
Each of these has its own guide with the full data, the causes and a tracking plan.
- Nausea (44%). The most common side effect, usually strongest a day or two after a shot and after each dose step. Full guide
- Diarrhea (30%). Mostly during dose increases; fluids and electrolytes matter most. Full guide
- Vomiting (24%). Usually comes with nausea, so the nausea guide covers it. Full guide
- Constipation (24%). Slower digestion plus eating less; fiber, fluids and movement help. Full guide
- Stomach pain, bloating and gas (6–20%). Usually mild and tied to slower digestion. Severe or lasting pain is different: call your prescriber.
- Headache (14%). Often linked to dehydration, long gaps without food or cutting back on caffeine. Full guide
- Fatigue (11%). Usually from eating and drinking much less in the first weeks. Full guide
- Heartburn, indigestion and burping (5–9%). Food stays in the stomach longer. Full guide
- Dizziness (8%). More likely when you're dehydrated or your blood pressure falls as you lose weight.
- Hair loss (3%). Temporary shedding (telogen effluvium) a few months in, linked to fast weight loss.
- "Ozempic face." Not a side effect of the drug on your skin: it's the look of losing fat from the face quickly, which can make it appear thinner or older. It reflects the speed of weight loss rather than anything specific to Ozempic.
Why does Ozempic cause side effects?
Ozempic (semaglutide) is a GLP-1 receptor agonist. It mimics GLP-1, a gut hormone (an incretin) that signals fullness to your brain and slows how quickly your stomach empties (gastric emptying). That's what quiets appetite and food noise, and it's also where most side effects come from:
- Slower gastric emptying brings fullness, nausea, burping, heartburn and constipation.
- A gut that's adjusting brings diarrhea, bloating and gas, mostly in the first weeks of each dose.
- Eating far less means fewer calories, less fluid and often less protein, which can lead to tiredness, headaches, dizziness and, a few months in, hair shedding.
- Dose steps restart the adjustment, so side effects often return for a week or two after each increase.
How long do Ozempic side effects last?
For most people, Ozempic side effects last a few weeks after starting and after each dose increase, then fade. Within each week, many people notice them most a day or two after the shot: semaglutide reaches its highest level 1–3 days after an injection. It settles into a steady weekly level after about four to five weeks at the same dose, which is why side effects usually calm down once you've stayed on a dose for a month or so.
| Side effect | How long it usually lasts | When to call your prescriber |
|---|---|---|
| Nausea | A few days after each shot; eases over weeks at a stable dose | You can't keep food or fluids down |
| Diarrhea | A few days per episode, mostly during dose increases | It lasts more than a couple of days, or comes with blood, fever or dizziness |
| Constipation | Can linger longer than other stomach side effects | No bowel movement for more than three days, or severe pain |
| Headache | Hours to a day, usually on low-fluid or low-food days | It's sudden and severe, or comes with vision changes or confusion |
| Fatigue | The first weeks and after each dose step | It doesn't lift after a few weeks on the same dose |
| Hair loss | Starts two to four months in; regrowth within six to twelve months | Shedding lasts more than six months or comes in patches |
Semaglutide's half-life is about one week, so after a last dose it takes around five weeks to leave your body, and side effects fade over that time.
Track your Ozempic side effects with a GLP-1 app and stay in control: your 30-day plan
On Ozempic, side effects can hit a day or two after the shot and last into the week, which makes them easy to blame on everything else. An Ozempic progress tracker shows you what's really going on: log how you feel each day next to your Ozempic doses, and you're in control. You'll know which day after your shot each side effect peaks, whether a dose step brought it on and whether it's easing, and you'll walk into your next appointment with facts instead of guesses.
Why Glapp? It's a top-rated GLP-1 tracking app used by 100,000+ people, rated 4.8/5 on Trustpilot and the App Store, and 4.6/5 on Google Play. Glapp grew out of Reddit GLP-1 support groups and is built by people who take GLP-1 medications themselves, so most of what's in it came straight from what the community asked for: daily side-effect check-ins, an estimated Ozempic level, custom titration curves for your dose steps and a doctor's report you can share. It's grounded in published clinical trial data and peer-reviewed research, core tracking is free, and it syncs across iPhone, Android and web. Here's how to use it over your first 30 days.
Glapp does not provide medical advice or treat side effects. It shows your daily check-ins against your estimated medication levels so you have structured data to share with your prescriber.
Day 1: Start tracking your side effects
Use Glapp's daily check-in to record any side effect you notice, from nausea to headaches, and rate how severe it feels. Log your Ozempic dose and injection time too, so everything that follows is based on what you actually took.
Daily entries help you see whether each side effect is getting better, getting worse or staying the same. You'll have a clear record of how you felt, without having to remember every day.
Day 3: Compare symptoms with your estimated Ozempic level
Glapp estimates your medication level throughout the day using your dose and injection time. Ozempic typically reaches its highest blood concentration 1–3 days after an injection.
Seeing your symptoms alongside this estimate helps you spot when each side effect appears within your shot cycle. As you log more days, you can look for a repeating pattern and know when to pay closer attention.
The medication level is an estimate, not a blood test, and a matching pattern does not prove what caused your symptoms.
Day 7: See how your side effects change over time
Open the side-effects chart in the Progress tab and choose the period you want to review. Your daily ratings appear on a timeline, making it easier to see whether a difficult day was an isolated episode or part of a longer trend.
Day 14: Look for patterns in your weekly report
Glapp's weekly progress report brings your logged data together, with dedicated sections showing your side effects and how they change.
Do side effects return on the same day after your shot? Did they start after a dose step? Do they coincide with changes in hunger or food noise? Reviewing two weeks of entries can help you spot patterns that are easy to miss day by day, and give you specific questions to discuss with your doctor.
Day 30: Bring a clear record to your doctor
After a month, review the bigger picture: are your side effects becoming less frequent, staying the same or getting worse? Ozempic generally reaches a steady repeating level after about four to five weeks of weekly injections at the same dose.
Create a doctor's report in Glapp and choose the information to include. Your doctor can review your symptom history alongside your doses and progress, giving you a more focused conversation about your treatment and your next dose step.
Start tracking your Ozempic side effects in Glapp
Ozempic side effects by dose: what changes at each step
Ozempic starts low and steps up at least four weeks apart:
| Step | Weekly dose | What to expect |
|---|---|---|
| Weeks 1–4 | 0.25 mg | Starter dose; mild side effects are common as your body meets the medication |
| Week 5 onward | 0.5 mg | First step up; a new week or two of adjustment |
| After at least 4 more weeks, if increased | 1 mg | Appetite drops further; watch fluids and protein |
| After at least 4 more weeks, if increased | 2 mg | Highest Ozempic dose; side effects usually settle within weeks |
The weight-loss trial figures are at 2.4 mg and aren't broken down by step, so your own log is the best guide to what each step does for you. If side effects get hard to manage after a step, prescribers can keep you on a dose for longer before the next one.
What to bring to your prescriber
Glapp's doctor's report puts your side effects, doses and progress on one page. Before your appointment, check it shows:
- which side effects you had and how severe they were
- which day after your shot they peaked
- whether they started after a dose step
- any day you couldn't eat or keep fluids down
Questions you could ask. They're conversation starters, not recommendations; your prescriber decides what, if anything, to change.
- "My nausea is worst two days after my shot. Is that expected on Ozempic?"
- "Should I stay on this dose longer before stepping up?"
- "Which side effects should make me call you straight away?"
Frequently asked questions
How long do Ozempic side effects last?
Usually a few weeks per dose. Side effects are strongest in the first one to two weeks after starting and after each increase, peak a day or two after each shot, and settle once you've been on the same dose for about a month. Hair shedding is the exception: it starts later and takes months to grow back.
What are the most common side effects of Ozempic?
Nausea, diarrhea, vomiting and constipation, followed by abdominal pain, headache and fatigue. In weight-loss trials of semaglutide 2.4 mg, nausea affected 44% of adults and diarrhea 30%.
Are Ozempic and Wegovy side effects the same?
Both contain semaglutide, so the same side effects are expected. Wegovy is the version approved for weight loss and goes up to 2.4 mg, while Ozempic's highest dose is 2 mg, so side effects at Ozempic's doses may be slightly less common. See Wegovy side effects.
Do Ozempic side effects go away?
Yes, for most people. Stomach side effects were most common during dose increases and were mostly mild to moderate and temporary in STEP 1, and more than 9 in 10 people stayed on treatment.
What is "Ozempic face"?
It's the thinner, sometimes older-looking face some people notice after losing weight quickly. It comes from losing facial fat, not from a direct effect of semaglutide on the skin, and it can happen with fast weight loss on any medication or none.
How do I track Ozempic side effects?
Log them in Glapp's daily check-in and rate each one low, medium or high, next to your Ozempic dose. Glapp shows each rating against your estimated medication level, and your weekly reports show which day after the shot each side effect peaks.
About the data
Ratings are self-reported and medication levels are estimated from dose and timing, not measured. Trial figures come from FDA-approved semaglutide weight-loss trials. This page is for information only and is not medical advice; talk to your prescriber about any side effect.
About the author
We're GLP-1 patients and health tech professionals, building Glapp in collaboration with doctors. About us
Sources
- Novo Nordisk. Wegovy (semaglutide) injection prescribing information: Table 3, warnings and precautions, pharmacokinetics.
- Wilding JPH, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med. 2021;384:989–1002.
- Novo Nordisk. Ozempic (semaglutide) injection prescribing information: dosage and administration.