GLP-1 Side Effects by Week: What Labels Say

GLP-1 side effects are reported by dose, not by week, and the labels' tables show most of them rising as the dose steps up. Nausea carries the highest rate, or ties for it, among the reactions quoted here: 15.8% to 20.3% on Ozempic, 44% on Wegovy 2.4 mg, 12% to 18% on Mounjaro and 25% to 29% on Zepbound, against 4% to 16% on placebo.

Each label's own escalation schedule supplies the weeks, so this guide lines the two up. The percentages come from different populations and doses, so they are not interchangeable. The prescriber decides every dose, and nothing here suggests a change.

In short

• The Ozempic label reports nausea in 15.8% of people on 0.5 mg and 20.3% on 1 mg, against 6.1% on placebo.
• The Wegovy label reports nausea in 44% on 2.4 mg against 16% on placebo, and the Zepbound label reports 25% to 29% across its doses.
• The Ozempic and Mounjaro labels name persistent or severe abdominal pain as the pancreatitis warning sign, and the Zepbound label links GI reactions that lead to dehydration (nausea, vomiting or diarrhea) to kidney injury.

What do the labels report about GLP-1 side effects, week by week?

The four prescribing labels report side effects as the share of trial participants with each reaction at each dose, and they set the weeks through their escalation schedules.

The adverse reactions tables are organised by dose arm, not by week. The weeks in this guide come from each label's Section 2 dosing text. The percentages come from Section 6.1, the adverse reactions tables. Putting the two side by side is the article's own layout, and it shows where in the ladder each dose arm sits.

The guide answers these questions in reading order:

• When do side effects start, and what happens in weeks 1 to 4?
• What changes in weeks 5 to 8?
• What do weeks 9 to 16 look like?
• What do the labels report from week 17 onward, at maintenance dose?
• Do side effects get better, or come back with each dose increase?
• How does Ozempic's nausea rate compare with Mounjaro's?
• Which warning signs mean it is time to call a doctor?
• How can day-by-day tracking sit next to a dose log?

When do GLP-1 side effects start, and what happens in weeks 1 to 4?

Weeks 1 to 4 are the starting dose on all four labels: 0.25 mg for Ozempic and Wegovy, and 2.5 mg for Mounjaro and Zepbound, according to each label's dosing section.

The Mounjaro and Zepbound labels both state that 2.5 mg is not a maintenance dose. It is the first step of a ladder, and each label sets its own minimum time before the next step.

The figures quoted in this guide do not include a rate for the starting dose alone. They also give no hour or day when effects begin. The tables cover 0.5 mg and 1 mg for Ozempic, 5 mg and above for Mounjaro and Zepbound, and 2.4 mg for Wegovy. An exact "day 2" claim is therefore not something these labels support.

There is a reason to expect a build-up. The Ozempic label gives semaglutide an elimination half-life of about 1 week. With a half-life of 1 week, about half of a dose is still present when the next weekly dose arrives. That is the article's arithmetic, not a label statement, but it shows how a level can climb over several weeks.

The Zepbound label also asks for kidney function to be monitored, especially during dose initiation and escalation. To see how logged doses overlap, you can estimate how much medication may still be active from logged doses. For nausea specifically, read how long Ozempic nausea tends to last and its warning signs.

What changes in weeks 5 to 8?

Weeks 5 to 8 are the first step up on all four labels, and the Ozempic label reports nausea in 15.8% of people on 0.5 mg, against 6.1% on placebo.

The schedules differ in detail:

• Ozempic moves to 0.5 mg from week 5.
• Wegovy uses 0.5 mg for weeks 5 to 8.
• Zepbound's label says to increase to 5 mg after the 2.5 mg weeks.
• Mounjaro's label allows a 2.5 mg step after at least 4 weeks on the current dose.

At this step, the Ozempic label also lists vomiting in 5% (2.3% on placebo) and diarrhea in 8.5% (1.9% on placebo). These come from placebo-controlled type 2 diabetes trials.

The Mounjaro label lists nausea in 12% on 5 mg against 4% on placebo, in type 2 diabetes trials. The Zepbound label lists 25% on 5 mg against 8% on placebo, with diarrhea at 19% against 8%, in weight-reduction trials.

One caution applies to every figure in this section. The percentage covers the whole trial period for people assigned to that dose, so it is not a count of what happened in weeks 5 to 8. It shows how common the reaction was among people assigned to that dose.

What do weeks 9 to 16 look like?

Weeks 9 to 16 are where the labels' schedules differ: Wegovy sets 1 mg for weeks 9 to 12 and 1.7 mg for weeks 13 to 16, while the other three labels make later steps optional.

Ozempic's label allows an increase to 1 mg after at least 4 more weeks at 0.5 mg, so week 9 is the earliest. It then allows 2 mg after at least 4 more weeks, so week 13 is the earliest. The label reports nausea in 20.3%, vomiting in 9.2% and diarrhea in 8.8% on 1 mg.

Mounjaro and Zepbound allow 2.5 mg steps after at least 4 weeks on the current dose. The arithmetic shows how late the higher doses come: 2.5 mg (weeks 1 to 4), 5 mg (5 to 8), 7.5 mg (9 to 12), 10 mg (13 to 16), 12.5 mg (17 to 20), then 15 mg at week 21 at the earliest. The prescriber decides whether and when any step happens.

The label rates do not climb in a straight line:

• Mounjaro nausea: 12% on 5 mg, 15% on 10 mg, 18% on 15 mg.
• Zepbound nausea: 25%, 29% and 28% across the same three doses.
• Zepbound constipation: 17%, 14% and 11%.

Higher doses do not raise every reaction.

What do the labels report from week 17 onward, at maintenance dose?

From week 17 onward, Wegovy's label sets maintenance at 1.7 mg or 2.4 mg, and its adverse reactions table for 2.4 mg lists nausea in 44% of people against 16% on placebo.

The same table, from weight-management trials with 2,116 adults on 2.4 mg and 1,261 on placebo, lists:

• diarrhea 30% against 16%
• vomiting 24% against 6%
• constipation 24% against 11%
• abdominal pain 20% against 10%
• headache 14% against 10%
• fatigue 11% against 5%

Wegovy's label also covers an optional 7.2 mg dose (Wegovy HD) after at least 4 weeks at 2.4 mg. In that separate comparison, nausea was 13% on placebo, 35% on 2.4 mg and 39% on 7.2 mg. Vomiting was 6%, 16% and 22%. Note that 2.4 mg shows 35% here and 44% in the first table. The populations differ, which is why a figure needs its trial attached.

For tirzepatide, the Zepbound label reports fatigue in 5%, 6% and 7% on 5, 10 and 15 mg, against 3% on placebo. Read what the labels say about fatigue on Zepbound, Wegovy, Mounjaro and Ozempic for the full picture. Wegovy's and Zepbound's label hair-loss figures are covered in their own guide.

For readers relating side effects to progress, Zepbound's week-72 results by dose are laid out there. In SURMOUNT-1, a 72-week trial in 2,539 adults without diabetes, the average weight change was 3.1% on placebo, 15.0% on 5 mg, 19.5% on 10 mg and 20.9% on 15 mg. Those are averages for that population, dose and time.

Do GLP-1 side effects get better, or come back with each dose increase?

The labels do not report a week-by-week course, so they cannot show on their own whether effects fade or return, but their dose-arm rates rise with dose for most reactions.

On the Ozempic label, nausea goes from 15.8% on 0.5 mg to 20.3% on 1 mg, and vomiting from 5% to 9.2%. On the Mounjaro label, nausea goes from 12% to 15% to 18% across 5, 10 and 15 mg. A higher dose arm reports more of these reactions.

The Zepbound label asks for kidney function monitoring especially during dose initiation and escalation. It states that most reported acute kidney injury occurred in people whose GI reactions led to dehydration.

What the tables do not show is how long any reaction lasts after a step. No label quoted here gives a day count, so this guide does not put one on it. The label tables here do not show whether reactions ease or return after a step, so the prescriber is the person to ask.

Day-by-day ratings next to dose dates let you compare your own symptoms with your logged doses.

How does Ozempic's nausea rate compare with Mounjaro's?

The Ozempic label reports nausea in 15.8% of people on 0.5 mg and 20.3% on 1 mg, and the Mounjaro label reports 12%, 15% and 18% on 5, 10 and 15 mg, both in placebo-controlled type 2 diabetes trials.

The comparison is not like for like. The placebo groups differ: 6.1% for Ozempic and 4% for Mounjaro. The doses differ, and each label has its own trial population and its own set of arms. The Ozempic table has two active arms and the Mounjaro table has three.

For weight management, Wegovy's label reports 44% on 2.4 mg and Zepbound's reports 25% to 29% across doses. Those are different medicines, trials and populations again.

This guide does not rank one medicine above another. It reports each label's own numbers with their populations and leaves the choice to you and your prescriber.

If you want to see how many weeks each label allows between steps, the full label dose chart for every medicine this guide covers lays out each schedule. Wegovy and Zepbound have their own pages, Wegovy's schedule and Zepbound's schedule.

What warning signs mean it is time to call a doctor?

The Ozempic and Mounjaro labels name persistent or severe abdominal pain, sometimes radiating to the back, with or without nausea or vomiting, as the warning sign of pancreatitis.

Other label warnings sit alongside it:

• Gallbladder disease. The Mounjaro label says suspected gallstones (cholelithiasis) call for gallbladder diagnostic studies and clinical follow-up.
• Dehydration and kidney injury. The Zepbound label says most reported acute kidney injury occurred in people with GI reactions leading to dehydration, meaning nausea, vomiting or diarrhea. It asks for kidney function monitoring, especially during dose initiation and escalation.
• Severe gastroparesis. The Zepbound label does not recommend the medicine in people with severe gastroparesis.

The Zepbound label also notes that GI reactions can be severe.

These are the labels' own warnings, not a complete symptom checker. If you have pain like the one described, or vomiting or diarrhea you cannot keep up with, contact a doctor or emergency care promptly. What happens with the medicine afterwards is a decision for your prescriber.

Which figures does each label give, side by side?

The two tables below set each label's own escalation weeks beside its own dose-arm rates, all taken from the DailyMed labels' dosing sections and Section 6.1 tables.

First, the weeks each label's schedule sets. Optional steps show the earliest timing only.

Second, the reaction rates by dose arm, each in its own population.

Read across a row to see how one reaction changes with dose. Do not read down a column as a ranking, because the populations differ.

Which mistakes are easy to make when reading side effect tables?

Two mistakes are easy to make with label tables: reading a trial percentage as a weekly rate, and comparing numbers from different trials as if they were one.

• Do not read a dose-arm percentage as a weekly rate. The label shows how common a reaction was among people on that dose, not what happened in a given week. The full label dose chart for every medicine this guide covers shows where each dose sits in its schedule.
• Do not compare percentages across labels without checking the population. Type 2 diabetes and weight-management trials differ, and so do placebo rates. Read how long Ozempic nausea tends to last and its warning signs for one label's picture in depth.
• Do not assume the medicine is gone the week after a dose. With a label half-life of about 1 week for semaglutide, the level falls gradually. Estimate how much medication may still be active from logged doses.
• Do not wave away warning signs as ordinary nausea. Persistent or severe abdominal pain and signs of dehydration are named by the labels. The side effects guides cover each symptom with its sources.
• Do not decide a dose change from a table. The schedules above are quoted from the labels, and the prescriber decides every step.

How does Dose & Lose track side effects day by day?

Dose & Lose lets you rate symptoms such as nausea and fatigue from 0 to 10 each day and see them over time next to your logged doses.

The dose log records the medication, dose, date and time, injection site, a pain level from 0 to 10 and notes. The app also draws an estimate of how much medication is active from your logged doses. It is an estimate, not a lab value.

Dose & Lose is a tracking app. It does not prescribe, give dosing advice or measure anything in the body. The app's interface is in English only. You can see how Dose & Lose will log side effects day by day next to doses.

Frequently asked questions

How long do GLP-1 side effects usually last?

The labels do not give a day count. Their tables report the share of trial participants with each reaction at each dose, not how long it lasted, so no label number answers this. Ozempic nausea has its own guide that covers what is known and the warning signs that need a doctor.

How common is nausea on Ozempic compared with Mounjaro?

Both labels report nausea at rates that rise with dose, but not from the same trials. The Ozempic label lists nausea in 15.8% on 0.5 mg and 20.3% on 1 mg, and the Mounjaro label lists 12%, 15% and 18% on 5, 10 and 15 mg, all in type 2 diabetes trials.

What are the warning signs of pancreatitis on a GLP-1?

The Ozempic and Mounjaro labels name persistent or severe abdominal pain, sometimes radiating to the back, with or without nausea or vomiting, as the pancreatitis warning sign. Anyone with that pain should contact a doctor promptly. What happens with the medicine afterwards is the prescriber's decision.

What happens to side effects after stopping a GLP-1 medicine?

The labels quoted here report on-treatment rates, so they give no figure for after stopping. The Ozempic label gives semaglutide a half-life of about 1 week, which means the medication level falls gradually over weeks rather than at once. Any symptom after stopping is worth raising with your prescriber.

Is nausea a sign the dose is too high?

The labels do not say whether nausea means a dose is too high. The Ozempic label reports nausea in 6.1% on placebo and in 15.8% to 20.3% on semaglutide. Whether any dose should change is for the prescriber, and severe or persistent pain needs a doctor.

Sources

Every figure above comes from these record-level sources.

• Ozempic (semaglutide) prescribing information, DailyMed: dose schedule, adverse reaction rates by dose, half-life and pancreatitis warning.
• Wegovy (semaglutide) prescribing information, DailyMed: dose schedule up to 7.2 mg and adverse reaction rates.
• Mounjaro (tirzepatide) prescribing information, DailyMed: dose schedule, adverse reaction rates, pancreatitis and gallbladder warnings.
• Zepbound (tirzepatide) prescribing information, DailyMed: dose schedule, adverse reaction rates, SURMOUNT-1 results, dehydration and kidney warnings.
• Jastreboff et al., SURMOUNT-1, N Engl J Med 2022: the 72-week tirzepatide trial.

Published by Petros IT Solutions SRL under the byline Dose & Lose Editorial Team. This guide is educational and is not personal medical advice. Corrections: office@doseandlose.com.