Key takeaways
- Nausea is reported at 25% to 29% on Zepbound but 12% to 18% on Mounjaro, the same molecule at the same doses, in two different trial populations.
- Nausea, diarrhea and vomiting are the three most common reactions on the Zepbound label.
- Constipation runs backwards: 17% at 5 mg falling to 11% at 15 mg.
- The boxed warning concerns thyroid C-cell tumors in rats; the label states human relevance "has not been determined."
- On oral contraceptives, the label says use a backup method for 4 weeks after starting and after every dose increase.
- Tell your surgical team, because the label warns of aspiration risk under anesthesia.
- No incidence figures exist for compounded tirzepatide. It has no FDA-approved label.
Sources: US prescribing information for Zepbound and Mounjaro (Eli Lilly), checked by Nudge on 19 October 2026. Nudge is a tracking app, not a medical provider. This page reports what the labels say and is not medical advice.
Where you are in your journey
Most of the rough stuff happens when your dose changes, not at random.
The label is unusually direct about this. In the Zepbound trials,"the majority of nausea, vomiting, and/or diarrhea events occurred during dose escalation". In other words: the first few weeks, and then again each time you step up. The stretches in between are usually the easier part.
Everyone starts at 2.5 mg, which is a starting dose rather than a treating dose. You stay there four weeks, then move up in 2.5 mg steps, spending at least four weeks at each one, until you reach whatever dose works for you.
| Dose | Roughly when | What tends to happen |
|---|---|---|
| 2.5 mg | Weeks 1 to 4 | Starting dose. Not meant to treat yet, just to let your body meet the drug. |
| 5 mg | Weeks 5 to 8 | The first dose studied as a maintenance dose. Nausea peaks around here for many. |
| 7.5 mg | Weeks 9 to 12 | A step up, so expect the rough days to come back for a while. |
| 10 mg | Weeks 13 to 16 | A common place to stop. Nausea highest on the label here, at 29%. |
| 12.5 mg | Weeks 17 to 20 | Another step, only if you and your prescriber decide to go further. |
| 15 mg | Week 21 onwards | The maximum. Vomiting and diarrhea are most common at this dose. |
Severe reactions, as opposed to uncomfortable ones, stay uncommon but do rise with the dose: 1.7% of people at 5 mg, 2.5% at 10 mg and 3.1% at 15 mg, against 1% on placebo.
Check which step your prescribed dose is, and convert it to syringe units →
What the week after a shot feels like
There is a rhythm to it, and it follows the drug.
Tirzepatide reaches its peak in your blood about 24 hours after the injection, though the label gives a range of 8 to 72 hours, so some people peak on day one and others closer to day three. It then clears slowly, with a half-life of 5 to 6 days, which is why it is a weekly shot.
The labels do not publish a day-by-day symptom timeline, so the table above is the drug's timing rather than a promise about yours. What it is useful for is spotting your own pattern. If you always feel worst on the same day, that is worth knowing, and worth telling whoever prescribes for you.
See your estimated medication level between shots →
What are the side effects of tirzepatide, by dose?
Here is every side effect on the labels, and how many people had it at each dose.
The placebo column is the one to watch. If 8 people in 100 felt sick on a dummy injection, then some of what you read about is not the drug. Comparing the two columns tells you what tirzepatide is actually adding.
| Adverse reaction | Placebo | 5 mg | 10 mg | 15 mg |
|---|---|---|---|---|
| Nausea | 8% | 25% | 29% | 28% |
| Diarrhea | 8% | 19% | 21% | 23% |
| Constipation | 5% | 17% | 14% | 11% |
| Vomiting | 2% | 8% | 11% | 13% |
| Abdominal pain | 5% | 9% | 9% | 10% |
| Dyspepsia (indigestion) | 4% | 9% | 9% | 10% |
| Injection site reactions | 2% | 6% | 8% | 8% |
| Fatigue | 3% | 5% | 6% | 7% |
| Hypersensitivity reactions | 3% | 5% | 5% | 5% |
| Eructation (burping) | 1% | 4% | 5% | 5% |
| Hair loss | 1% | 5% | 4% | 5% |
| Gastroesophageal reflux | 2% | 4% | 4% | 5% |
| Flatulence | 2% | 3% | 3% | 4% |
| Abdominal distension | 2% | 3% | 3% | 4% |
| Dizziness | 2% | 4% | 5% | 4% |
| Hypotension | 0% | 1% | 1% | 2% |
| Adverse reaction | Placebo | 5 mg | 10 mg | 15 mg |
|---|---|---|---|---|
| Nausea | 4% | 12% | 15% | 18% |
| Diarrhea | 9% | 12% | 13% | 17% |
| Decreased appetite | 1% | 5% | 10% | 11% |
| Vomiting | 2% | 5% | 5% | 9% |
| Constipation | 1% | 6% | 6% | 7% |
| Dyspepsia | 3% | 8% | 8% | 5% |
| Abdominal pain | 4% | 6% | 5% | 5% |
How common is nausea on tirzepatide?
Roughly one in four people felt sick, and it is the most common thing people report.
On Zepbound it was 25% at 5 mg, 29% at 10 mg and 28% at 15 mg, against 8% on placebo. On Mounjaro, the same drug at the same doses, it was 12%, 15% and 18%. You will see a lot of pages quote "12% to 29%" as one range. That range is really two different studies of two different groups of people, so it does not describe anyone in particular. If you are taking it to lose weight, the Zepbound numbers are the ones about people like you.
Put another way: about one in five people had nausea that cannot be explained by expecting it.
Does tirzepatide get worse as the dose goes up?
Usually yes, but not for everything, and not forever.
Vomiting is the clearest case: 8% at 5 mg, 11% at 10 mg, then 13% at the top dose. Nausea climbs between 5 and 10 mg, then flattens. Constipation actually gets less common the higher you go.
One thing the labels cannot tell you is timing. They count how many people had something at some point, not when it started or how long it lasted. So if you read a confident claim that nausea lasts exactly two weeks, that number came from somewhere other than the label.
Work out where you are in the titration schedule with the tirzepatide dose calculator →
Does tirzepatide cause diarrhea?
Yes, for about one in five people, and unlike most of these it keeps rising with the dose.
On Zepbound it runs 19%, 21% then 23%, against 8% on placebo. On Mounjaro it is much closer to the placebo group, 12% to 17% against 9%, so in those trials it barely separated from chance.
Set a daily fluid target with the hydration calculator →
How common is vomiting on tirzepatide?
Less common than nausea. About one in twelve people at the starting dose, rising to roughly one in eight at the top.
That is 8%, 11% and 13% on Zepbound against 2% on placebo, and 5%, 5% and 9% on Mounjaro. It matters more than it sounds, because vomiting and diarrhea together are how people get dehydrated, which is what the kidney warning on the label is about.
Does tirzepatide cause constipation?
Yes, and it is the one that tends to ease rather than worsen as your dose goes up.
On Zepbound it starts at 17% on the lowest dose and falls to 11% on the highest, against 5% on placebo. On Mounjaro it is lower throughout, 6% to 7% against 1%.
What are the serious side effects of tirzepatide?
Most side effects are uncomfortable rather than dangerous. These ten are the ones the FDA wants you told about.
Mounjaro lists the same ten, ordered differently, with hypoglycemia scoped to people also taking insulin or insulin secretagogues.
- Risk of thyroid C-cell tumors (5.1)
- Severe gastrointestinal adverse reactions (5.2)
- Acute kidney injury due to volume depletion (5.3)
- Acute gallbladder disease (5.4)
- Acute pancreatitis (5.5)
- Hypersensitivity reactions (5.6)
- Hypoglycemia (5.7)
- Diabetic retinopathy complications in patients with type 2 diabetes (5.8)
- Pulmonary aspiration during general anesthesia or deep sedation (5.9)
- Never share a KwikPen between patients (5.10)
Two of those catch people out. Number 9 matters before any procedure, because your surgical team needs to know you take tirzepatide. Number 10 is not a hygiene footnote. Sharing a pen risks transmission of blood-borne pathogens even if the needle is changed.
What does the boxed warning actually say?
It is about thyroid tumours found in rats, and the label is careful to say nobody knows yet whether that applies to people.
In rats, tirzepatide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures. It is unknown whether ZEPBOUND causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans as human relevance of tirzepatide-induced rodent thyroid C-cell tumors has not been determined.
Tirzepatide is contraindicated with a personal or family history of medullary thyroid carcinoma, or with MEN 2. Contraindicated means the label says do not use it, not "discuss the risks."
You will find pages calling this a cancer risk and others brushing it aside. Neither matches what the label actually says, which is quoted above in full so you can judge it yourself.
Does tirzepatide stop birth control pills working?
If you take the pill, you need backup contraception for four weeks after you start, and again after every single dose increase.
Advise patients using oral hormonal contraceptives to switch to a non-oral contraceptive method, or add a barrier method of contraception for 4 weeks after initiation with ZEPBOUND and for 4 weeks after each dose escalation.
The second half is the part people miss. It is not only when you start. Every time your dose goes up, the four weeks begins again, and on a normal titration schedule that can happen several times.
What happens if you get pregnant on tirzepatide?
The label's instruction is direct: "When pregnancy is recognized, discontinue ZEPBOUND."
A pregnancy exposure registry monitors outcomes in women exposed during pregnancy; patients and providers can register by calling 1-844-524-0039. On breastfeeding, section 8.2 reports that in a single-dose lactation study tirzepatide in breast milk was "either undetectable or low compared to the maternal administered dose," while noting there is not enough data on effects in breastfed infants.
Do I need to tell my surgeon I take tirzepatide?
Yes, and it is one of the ten label warnings, not a precaution someone invented.
Section 5.9 covers pulmonary aspiration during general anesthesia or deep sedation. These drugs slow gastric emptying, so the stomach may not be empty when an anesthetist assumes it is. Your surgical and anesthesia team need to know you take tirzepatide and when your last dose was, including for dental work under sedation and endoscopy.
Does tirzepatide cause hair loss?
The Zepbound label reports hair loss in 5% at 5 mg, 4% at 10 mg and 5% at 15 mg, against 1% on placebo.
It does not appear in the Mounjaro table at all. In the self-report data below, alopecia was recorded in 3.1% of reports across both drugs. The label does not explain a mechanism, and we are not going to supply one it does not claim.
Why does tirzepatide cause burping and a sulfur taste?
Burping is on the label as eructation: 4% at 5 mg and 5% at 10 and 15 mg, against 1% on placebo.
The sulfur or "rotten egg" taste people describe alongside it is not a labeled term, so there is no official figure for it. It sits with the other effects tied to slowed digestion: reflux at 4% to 5%, flatulence at 3% to 4%, abdominal distension at 3% to 4%.
Do injection site reactions happen?
Yes: 6% at 5 mg, 8% at 10 mg and 8% at 15 mg on the Zepbound label, against 2% on placebo.
Separately, warning 5.10 is about pens rather than sites: never share a KwikPen between patients, even if the needle is changed, because of blood-borne pathogen risk.
Does tirzepatide cause muscle loss?
The labels do not report muscle loss as an adverse reaction, and no incidence figure exists for it.
In the self-report data, muscle atrophy appeared in 0.7% of reports and myalgia in 1.9%. What is established is that weight lost rapidly from any cause includes lean mass as well as fat, a general finding about weight loss, not a tirzepatide-specific label claim.
Get a daily protein range based on your weight →
Does tirzepatide interact with alcohol?
Neither label lists alcohol as a contraindication or a labeled interaction, so there is no official figure or instruction to quote.
Anything giving a specific rule is not coming from the prescribing information. The one adjacent label fact: hypoglycemia is a listed warning, scoped on the Mounjaro label to people also using insulin or insulin secretagogues.
What do people actually report, outside the trials?
If you have been reading forums and wondering whether your experience is normal, somebody has actually counted.
Researchers at the University of Pennsylvania read 410,198 Reddit posts about semaglutide and tirzepatide, written between May 2019 and June 2025. Of the 67,008 people who said they were taking one of these drugs, 43.5% mentioned at least one side effect. Here is what the tirzepatide group talked about most.
Sehgal NKR, Tronieri JS, Ungar L, Guntuku SC, "Self-Reported Side Effects of Semaglutide and Tirzepatide in Online Communities," University of Pennsylvania.
| Symptom | Share of tirzepatide users reporting side effects |
|---|---|
| Nausea | 28.6% |
| Fatigue | 14.7% |
| Constipation | 12.9% |
| Diarrhea | 12.5% |
| Vomiting | 11.1% |
| Injection site reactions, myalgia, insomnia, chills | 1% to 4% each |
People discussing semaglutide reported nausea at 39.4% and vomiting at 18.0%, noticeably higher than tirzepatide on both.
What is interesting is where the two agree and where they do not. Nausea and vomiting match almost exactly: 29% on the label against 28.6% in the posts, and 11% against 11.1%. Fatigue does not match at all. The label says 5% to 7%. People report it at 14.7%, making it the second most discussed symptom of the lot.
Some things people report are not on the label at all. Reproductive and menstrual symptoms appeared in 3.8% of reports, and temperature complaints, meaning chills and feeling cold, in 1% to 4%. The authors describe these as "unrecognized potential effects" that are "not well captured in current labeling or trials."
Across both drugs, 65.8% of users with side effects reported at least one gastrointestinal symptom, and psychiatric symptoms were noted by 12.9%: anxiety 4.2%, insomnia 3.1%, depression 2.8%.
That gap is the useful part. If you are exhausted and the label says 6%, it is easy to talk yourself out of mentioning it. A lot of other people are describing the same thing. It is not proof the drug caused it, but it is a good reason to bring it up rather than assume it is just you.
Mounjaro vs Zepbound: is there a difference in side effects?
Same drug, same doses, different numbers, and the reason is who was in each study.
Mounjaro is approved for glycemic control in type 2 diabetes and to reduce major adverse cardiovascular events. Zepbound is the weight-management product. Neither set of numbers is "the real" rate for tirzepatide. If you are taking it for weight management, the Zepbound column describes a population like yours.
Do these rates apply to compounded tirzepatide?
No, and this is worth knowing before you compare prices.
Compounded tirzepatide has no FDA-approved label, so none of the numbers on this page were measured on it. That does not automatically make it riskier. It means that if someone quotes you a nausea rate for a compounded version, they have borrowed a figure from a product that was studied, and applied it to one that was not.
See which providers supply compounded versus brand-name tirzepatide, and what each charges →
Frequently asked questions
How long do tirzepatide side effects last?
The FDA labels report how many people experienced each reaction, not how long it lasted. No duration figure appears on either label, so any specific timeline you read comes from somewhere else.
What is the most common side effect of tirzepatide?
Nausea, at 29% at 10 mg on the Zepbound label, against 8% on placebo.
Does tirzepatide stop birth control pills working?
The label tells people on oral contraceptives to switch to a non-oral method or add a barrier method for 4 weeks after starting, and for 4 weeks after each dose increase.
Can tirzepatide cause hair loss?
The Zepbound label reports hair loss in 4% to 5% of people across doses, against 1% on placebo.
Does tirzepatide cause fatigue?
The Zepbound label reports fatigue in 5% at 5 mg, 6% at 10 mg and 7% at 15 mg, against 3% on placebo. Self-reported data puts it far higher, at 14.7%.
Do I need to tell my surgeon I take tirzepatide?
Yes. Both labels warn about pulmonary aspiration during general anesthesia or deep sedation.
Who should not take tirzepatide?
The label contraindicates it for anyone with a personal or family history of medullary thyroid carcinoma, or with Multiple Endocrine Neoplasia syndrome type 2.
Why do Mounjaro and Zepbound report different side effect rates?
They were studied in different populations, type 2 diabetes versus weight management, and each label reports only its own trials.
