Mounjaro side effects: label rates by dose
Mounjaro is tirzepatide, Eli Lilly's once-weekly injection approved by the FDA for type 2 diabetes, not for weight loss. That distinction matters for every number below: the rates in this guide come from Mounjaro's own diabetes trials, not from Zepbound, the brand name for tirzepatide's separate weight-loss indication, tested at the same doses in a different trial population. The figures come from the FDA prescribing information for Mounjaro, version 40 on DailyMed, dated September 2, 2026.
The most common side effects are gastrointestinal: nausea, diarrhea, vomiting, constipation, and abdominal pain, and most climb as the dose rises, though constipation and abdominal pain plateau or dip after the 5 mg dose. Mounjaro also has a boxed warning for thyroid C-cell tumors, the FDA's most prominent warning category. Because Mounjaro's trial population is routinely treated for diabetes with insulin or a sulfonylurea, the label tracks a hypoglycemia rate for those combinations that a weight-loss trial population does not generate in the same way.
This guide covers the label's dose-by-dose rates, the hypoglycemia numbers for insulin and sulfonylurea combination therapy, how long symptoms typically last, the serious warnings worth recognizing, what the label does and does not say about effects beyond the trial window, side effects specific to women, how Mounjaro compares with Ozempic in a head-to-head trial, and why the dose climbs as slowly as it does. The label's own pooled table below gives the exact figures.
Quick reference: Mounjaro side effects
- Nausea: 12% (5 mg), 15% (10 mg), 18% (15 mg), against 4% on placebo
- Hypoglycemia with a sulfonylurea: 13.8%, 9.9%, and 12.8% by dose. With basal insulin: 14% to 19% (16% at 5 mg, 19% at 10 mg, 14% at 15 mg), against 13% on placebo
- Most nausea, vomiting, and diarrhea happen during dose escalation and decrease over time. The label gives no median episode length in days
- Boxed warning: thyroid C-cell tumors in rats. Whether Mounjaro causes them in humans is unknown
- Hair loss: listed only under postmarketing experience for Mounjaro, with no clinical-trial rate
Educational information, not medical advice. Talk to your prescriber before changing how you take any medication.
Side effects of Mounjaro, by dose
Mounjaro is approved for type 2 diabetes. Zepbound, the brand name for tirzepatide's weight-loss indication, is tested at the same doses but in a different trial population, so its rates run higher and should not be blended with the ones below. The table pools two placebo-controlled trials in the FDA label.
| Side effect | Placebo | 5 mg | 10 mg | 15 mg |
|---|---|---|---|---|
| Nausea | 4% | 12% | 15% | 18% |
| Diarrhea | 9% | 12% | 13% | 17% |
| Vomiting | 2% | 5% | 5% | 9% |
| Constipation | 1% | 6% | 6% | 7% |
| Abdominal pain | 4% | 6% | 5% | 5% |
Mounjaro's 2.5 mg starting dose is a 4-week step before the first increase, and the label's pooled table above does not break it out on its own. Every rate in that table begins at the 5 mg dose and up. More people stopped Mounjaro for gastrointestinal reactions as the dose rose: 3.0 percent at 5 mg, 5.4 percent at 10 mg, and 6.6 percent at 15 mg, against 0.4 percent on placebo. Constipation and abdominal pain do not climb in a straight line with dose, but nausea, diarrhea, and vomiting do.
Hypoglycemia on Mounjaro with insulin or sulfonylureas
Mounjaro's label tracks a side effect that a weight-loss trial population does not generate the same way: low blood sugar when Mounjaro is combined with a sulfonylurea or with insulin. People with type 2 diabetes who take Mounjaro are often already on one of those drugs to manage blood sugar, so the label states plainly that "hypoglycemia was more frequent when MOUNJARO was used in combination with a sulfonylurea."
| Mounjaro dose | Any hypoglycemia | Severe hypoglycemia |
|---|---|---|
| 5 mg | 13.8% | 0.5% |
| 10 mg | 9.9% | 0% |
| 15 mg | 12.8% | 0.6% |
| Arm | Any hypoglycemia | Severe hypoglycemia |
|---|---|---|
| Placebo | 13% | 0% |
| 5 mg | 16% | 0% |
| 10 mg | 19% | 2% |
| 15 mg | 14% | 1% |
Neither table climbs in a straight line with dose, and the label offers no explanation for the pattern beyond the numbers themselves. Anyone on insulin or a sulfonylurea alongside Mounjaro has a reason to watch for the symptoms of low blood sugar that their prescriber already covers for those drugs on their own.
How long do Mounjaro side effects last
Mounjaro's label states, in these exact words, that "the majority of reports of nausea, vomiting, and/or diarrhea occurred during dose escalation and decreased over time." That is the label's only statement on timing. It names a pattern, not a count of days.
The clearest timing evidence the label gives is indirect: how many people stopped treatment, and when. Discontinuation for gastrointestinal reactions rose with dose, from 3.0 percent at 5 mg to 5.4 percent at 10 mg to 6.6 percent at 15 mg, against 0.4 percent on placebo. That pattern fits a side effect that is worst during the climb and eases at a steady maintenance dose, but it is not the same as a reported median length.
The label publishes no median length, in days, for one episode of Mounjaro nausea, vomiting, or diarrhea. The pooled analysis behind semaglutide's trials does report that figure for the other major GLP-1 molecule. See our pillar guide to how long do semaglutide side effects last for the week-by-week arc on that molecule. No equivalent has been published for tirzepatide, the molecule in Mounjaro.
Serious side effects of Mounjaro and warning signs
The serious side effects of Mounjaro are uncommon next to nausea or diarrhea, but the label asks prescribers and patients to recognize each one by its warning sign. These are the entries in the label's Warnings and Precautions and Adverse Reactions sections with a symptom a person can notice.
Pancreatitis. In the clinical trials, adjudicators confirmed 14 events of acute pancreatitis in 13 Mounjaro-treated adults, a rate of 0.23 per 100 patient-years, against 3 events in 3 comparator-treated patients, 0.11 per 100 patient-years. The label breaks none of this down by dose. The warning sign is persistent, severe abdominal pain, sometimes reaching the back, with or without nausea or vomiting. The label tells patients to discontinue Mounjaro promptly and contact their physician if pancreatitis is suspected.
Gallbladder disease. In placebo-controlled trials, acute gallbladder disease was reported by 0.6 percent of Mounjaro-treated patients and 0 percent of placebo-treated patients. The label tells patients they will be informed of the risk of acute gallbladder disease, which includes cholecystitis and gallstones.
Kidney injury from dehydration. No trial rate for this risk appears in the label. It reports postmarketing cases of acute kidney injury, some needing hemodialysis, and tells patients they will be informed of the potential risk of acute kidney injury due to dehydration, which is more likely after fluid loss from vomiting or diarrhea.
Allergic reactions. Hypersensitivity reactions of any kind were reported by 3.2 percent of Mounjaro-treated patients against 1.7 percent on placebo in the placebo-controlled pool. The label tells patients that serious hypersensitivity reactions have been reported with Mounjaro.
Injection site reactions. These were reported by 3.2 percent of Mounjaro-treated patients against 0.4 percent on placebo in the same pool.
Diabetic retinopathy. The label states that "temporary worsening of diabetic retinopathy has been reported with rapid improvement in glucose control," and tells prescribers to monitor patients with a history of diabetic retinopathy for progression.
No single discontinuation rate covering every adverse reaction appears in the label. Its only discontinuation figures by percentage are the gastrointestinal ones in the dose table above. The thyroid tumor warning, the label's most prominent, has its own section next.
Mounjaro and thyroid cancer risk
Mounjaro carries a boxed warning, the FDA's most prominent warning category, because "tirzepatide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors" in rats. A boxed warning rests on the strength of the evidence the agency requires prescribers to see first, and this one rests on animal data rather than confirmed human cases.
For people, the label's own words are direct: "it is unknown whether MOUNJARO causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans." The adverse reactions section of the label reports no thyroid cancer rate from the diabetes trials. Mounjaro "is contraindicated in patients with a personal or family history of MTC" and in anyone with Multiple Endocrine Neoplasia syndrome type 2, an inherited endocrine condition also known as MEN 2.
The label has been unable to answer the human question with trial data, since the longest SURPASS trial behind these rates ran up to 104 weeks, about two years, still short of the follow-up a slow-growing tumor needs to show up or rule out.
Mounjaro long term side effects
"Long term" is not a phrase the Mounjaro label defines with a number of years. Its adverse reaction tables come from the SURPASS placebo-controlled trials, which ran up to 40 weeks for most rates and up to 104 weeks for the sulfonylurea-combination hypoglycemia data, so every rate in this guide describes side effects over trial windows of two years or less, not true multi-year follow-up. What happens to a side effect rate at year three or year five on Mounjaro has not been reported in the label because the label's own trials did not run that long.
Two risks in this guide are explicitly framed around a longer horizon rather than a trial-length one. Diabetic retinopathy can temporarily worsen with rapid improvement in glucose control. The thyroid C-cell tumor question is the other: it is unresolved for humans precisely because tumors of that kind take years to develop, and no tirzepatide trial or postmarketing dataset has followed patients long enough to settle it. Beyond the rodent data already described, no long-term tirzepatide-specific cancer data exists.
Mounjaro side effects in women
Mounjaro's label has one instruction specific to women of reproductive age: oral contraceptives. The label states that "use of MOUNJARO may reduce the efficacy of oral hormonal contraceptives," and advises patients to "add a barrier method of contraception for 4 weeks after initiation and for 4 weeks after each dose escalation." That advice repeats at every step up the dose ladder, not only at the start.
On hair loss, Mounjaro's own label is narrower than its weight-loss counterpart. Alopecia appears in Mounjaro's label only under postmarketing experience, the section for reports gathered after approval rather than measured in a controlled trial, and the label gives no percentage for it. Zepbound's weight-loss trials do report a clinical-trial hair loss rate at the same doses; for that figure and the reasoning behind rapid weight loss and shedding, see our guide to zepbound side effects. The label gives no comparable number for Mounjaro, and none should be assumed.
Mounjaro vs Ozempic side effects in a head-to-head trial
Separate label tables cannot answer which drug causes more side effects, because each trial enrolled different people under different conditions.
For the full breakdown, see Mounjaro vs Ozempic.
Why the Mounjaro dose climbs slowly
The gastrointestinal side effects above are the reason Mounjaro's dose rises gradually instead of starting at the maintenance level. The label sets "the recommended starting dosage of MOUNJARO" at "2.5 mg injected subcutaneously once weekly," then has prescribers "increase the dosage in 2.5 mg increments after at least 4 weeks on the current dose." The maximum is 15 mg once weekly in adults and 10 mg once weekly in pediatric patients.
Each 4-week hold gives the digestive system time to adjust before the next step up, which is why discontinuation and side-effect rates in this guide are reported by maintenance dose rather than by week of treatment. For the full step-by-step chart, including when a prescriber might slow the climb further, see our guide to tirzepatide dosing guide. Changing a dosing schedule is a decision for your prescriber. Our Mounjaro medication page covers the drug itself, its approved use, and what it costs.
Frequently asked questions
What is the most common side effect of Mounjaro?
Nausea is the most common side effect of Mounjaro. In the FDA label's pooled placebo-controlled trials, nausea affected 12 percent of adults on the 5 mg dose, 15 percent on 10 mg, and 18 percent on 15 mg, against 4 percent on placebo. Diarrhea came close behind at 12 to 17 percent against 9 percent, and constipation and abdominal pain each ran in the single digits above their placebo rates. The label states that most reports of nausea, vomiting, and diarrhea occurred during dose escalation and decreased over time. These rates come from Mounjaro's own diabetes trials and should not be confused with Zepbound's higher weight-loss trial rates at the same doses.
How long do Mounjaro side effects last?
The label gives no median number of days for one episode of Mounjaro nausea, vomiting, or diarrhea. The FDA label states that most of these reports occurred during dose escalation and decreased over time, and discontinuation for gastrointestinal reactions rose with dose, from 3.0 percent at 5 mg to 6.6 percent at 15 mg, against 0.4 percent on placebo. That pattern points to symptoms easing once a person reaches a steady maintenance dose, but it is not the same as a reported duration. A pooled analysis exists for semaglutide's median episode length; no equivalent has been published for tirzepatide, the molecule in Mounjaro.
What are the long-term side effects of Mounjaro?
The Mounjaro label does not define long-term side effects with a number of years, because its own trials ran up to 104 weeks at most, about two years. Two risks are framed around a longer horizon within the label itself: diabetic retinopathy can worsen with rapid improvement in glucose control, a process that unfolds over months, and the thyroid C-cell tumor question remains unresolved for humans because tumors of that kind take years to develop and no trial or postmarketing dataset has followed patients that long. Beyond the rodent studies behind the boxed warning, no long-term tirzepatide-specific cancer data exists.
Does Mounjaro cause hypoglycemia with insulin or sulfonylureas?
Yes. The Mounjaro label states that hypoglycemia was more frequent when Mounjaro was combined with a sulfonylurea, where rates ran 13.8 percent at 5 mg, 9.9 percent at 10 mg, and 12.8 percent at 15 mg, with severe hypoglycemia up to 0.6 percent. Combined with basal insulin over 40 weeks, hypoglycemia ran 16 to 19 percent at the 5 mg and 10 mg doses and 14 percent at 15 mg, against 13 percent on placebo, with severe hypoglycemia up to 2 percent. Anyone taking Mounjaro alongside insulin or a sulfonylurea has reason to watch for the usual low-blood-sugar symptoms their prescriber already covers for those drugs.
Which is safer, Mounjaro or Ozempic?
Both drugs carry the identical boxed warning for thyroid C-cell tumors.