Mounjaro Side Effects: What the FDA Label Actually Reports

Before the side effects, one piece of housekeeping that trips up a lot of searches.

In the United States, Mounjaro is the type 2 diabetes drug. It contains tirzepatide, and as of August 2026 it is approved to improve blood sugar control in adults and children aged 10 and older with type 2 diabetes, and to reduce the risk of major cardiovascular events in adults with type 2 diabetes who are at high risk for them [1][3].

The same molecule, sold as Zepbound, is the US weight-management and sleep apnea product [2].

In the United Kingdom, Mounjaro is also the weight-loss brand. That is why a lot of “Mounjaro for weight loss” coverage online does not match the US label, and why UK adverse-reaction statistics for Mounjaro cover a completely different population of users [9]. If you are in the US and taking tirzepatide for weight, you are almost certainly on Zepbound.

This page covers the US Mounjaro label. Nothing here is medical advice.

What are the most common Mounjaro side effects?

The Highlights section names seven reactions reported in at least 5% of patients: nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia and abdominal pain [1].

Here are the figures from the pooled placebo-controlled type 2 diabetes trials, covering 718 adults who received tirzepatide [1]:

Side effect	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 (indigestion)	3%	8%	8%	5%
Abdominal pain	4%	6%	5%	5%

Two observations.

Decreased appetite is listed as a side effect here but not on Zepbound. That is not because the drug behaves differently. It is because in a diabetes trial, appetite loss is an unwanted effect to be recorded, while in a weight-loss trial it is the mechanism working. The same molecule, two framings.

The placebo column matters. Diarrhea was reported by 9% of people on placebo in these diabetes trials. A lot of what gets attributed to a drug happens anyway in a population with type 2 diabetes, many of whom are also on metformin.

Combining all gut reactions, 37.1%, 39.6% and 43.6% of people at 5, 10 and 15 mg had at least one, versus 20.4% on placebo [1].

Less common but separately quantified on the label: burping in about 2.5% to 3.3%, gas in 1.3% to 2.9%, bloating in 0.4% to 2.9%, reflux in 1.7% to 2.5%, injection site reactions in 3.2% overall, hypersensitivity reactions in 3.2%, dysesthesia (an odd or unpleasant skin sensation) in 0.4%, and altered taste in 0.1% [1].

How long do Mounjaro side effects last, and how many people quit?

The label says the majority of nausea, vomiting and diarrhea happened during dose escalation and decreased over time [1]. That is the single most useful sentence in the whole Adverse Reactions section, because it tells you the shape of the problem: front-loaded, tied to dose increases, and usually improving.

Discontinuation for gut side effects ran at 3.0%, 5.4% and 6.6% at 5, 10 and 15 mg, against 0.4% on placebo [1].

Over a much longer horizon, the four-year SURPASS-CVOT trial reported 13.3% of people stopping tirzepatide for adverse events versus 10.2% on dulaglutide, with the difference driven largely by gut events [5].

What warnings are on the Mounjaro label?

Ten, including the boxed warning. The numbering differs from Zepbound’s, but the content is the same set of items [1][2].

Boxed warning: risk of thyroid C-cell tumors (5.1)

Tirzepatide caused dose-dependent thyroid C-cell tumors in a two-year rat study. The label states it is unknown whether Mounjaro causes these tumors, including medullary thyroid carcinoma, in humans, because the human relevance has not been determined [1].

Routine calcitonin testing or thyroid ultrasound is described as being of uncertain value. The instruction is to report a neck lump, hoarseness, trouble swallowing or shortness of breath [1].

Acute pancreatitis (5.2)

Across the Mounjaro clinical program, 14 adjudicated pancreatitis events occurred in 13 tirzepatide-treated adults, a rate of 0.23 per 100 years of exposure, versus 3 events in 3 comparator-treated patients (0.11 per 100 years) [1]. In SURPASS-CVOT, adjudicated pancreatitis was 0.6% in both the tirzepatide and dulaglutide arms [5].

The postmarketing section separately lists hemorrhagic and necrotizing pancreatitis, sometimes fatal [1]. In January 2026 the UK regulator strengthened product information across the whole GLP-1 and dual GLP-1/GIP class, tirzepatide included, to highlight those rare presentations [7].

Hypoglycemia with concomitant insulin or a secretagogue (5.3)

This is the practical one for anyone on more than one diabetes drug.

• Monotherapy, 40 weeks: blood glucose under 54 mg/dL in 0% at every Mounjaro dose, versus 1% on placebo. No severe hypoglycemia in any arm [1].
• Added to basal insulin: under 54 mg/dL in 16%, 19% and 14% at 5, 10 and 15 mg, versus 13% on placebo. Severe hypoglycemia in 0%, 2% and 1% versus 0% [1].
• With a sulfonylurea, up to 104 weeks: under 54 mg/dL in 13.8%, 9.9% and 12.8%; severe in 0.5%, 0% and 0.6% [1].

The label says the risk may be lowered by reducing the dose of the insulin or the secretagogue. That is a prescriber decision, not something to do on your own.

Hypersensitivity reactions (5.4)

Reported in 3.2% versus 1.7% on placebo. Anaphylaxis and angioedema appear in the postmarketing section. Reactions were more frequent in people who developed anti-tirzepatide antibodies: 4.1% versus 3.0% [1].

About half of adults in the Mounjaro trials developed antibodies to tirzepatide (2,570 of 5,025). The label says these had no identified effect on how well the drug worked [1].

Acute kidney injury due to volume depletion (5.5)

A dehydration warning. The postmarketing section lists acute renal failure or worsening of chronic renal failure, sometimes requiring hemodialysis, and the label says most reported events occurred in people with nausea, vomiting or diarrhea severe enough to deplete fluid. In SURPASS-CVOT, investigator-reported acute kidney injury was 3.4% on tirzepatide versus 2.7% on dulaglutide [1][5].

No dose adjustment is recommended for kidney impairment, including end-stage kidney disease, but the label says to monitor kidney function in anyone reporting severe gut reactions [1].

Severe gastrointestinal adverse reactions (5.6)

Added in December 2025. Severe gut reactions occurred in 1.3%, 0.4% and 1.2% at 5, 10 and 15 mg versus 0.9% on placebo. The section states Mounjaro is not recommended in people with severe gastroparesis [1].

Diabetic retinopathy complications (5.7)

Updated in August 2026 on the basis of SURPASS-CVOT [1][4]. Rapid improvement in blood sugar control has been associated with temporary worsening of diabetic retinopathy. At baseline in the adult trials, 13% to 15% of participants had retinopathy on eye examination [1].

This is a different question from NAION, the sudden optic nerve injury that gets discussed in GLP-1 coverage. NAION does not appear on the Mounjaro label at all.

Acute gallbladder disease (5.8)

Reported in 0.6% versus 0% on placebo, combining gallstones, biliary colic and gallbladder removal [1]. Meta-analyses of tirzepatide trials have found a consistent increase in gallbladder and biliary disease, with one 2024 analysis of 12 trials reporting a relative risk of 1.52 for gallbladder or biliary disease overall.

Pulmonary aspiration during anesthesia or deep sedation (5.9)

Postmarketing reports describe people on GLP-1 drugs who had food left in the stomach at the time of a procedure despite fasting. The instruction is to tell healthcare providers about the drug before any planned surgery or procedure. The label says the data are insufficient to determine whether holding the drug would reduce risk [1].

Never share a MOUNJARO KwikPen between patients (5.10)

Added in January 2026. A KwikPen must never be shared even if the needle is changed, because of bloodborne pathogen risk [1].

What did the four-year SURPASS-CVOT trial find?

This is the best long-term safety dataset that exists for tirzepatide, and it is worth knowing what it does and does not tell you.

SURPASS-CVOT enrolled 13,299 adults with type 2 diabetes and established atherosclerotic cardiovascular disease, and followed them a median of four years against dulaglutide 1.5 mg. It was a noninferiority trial with an active comparator, so there was no placebo group [5].

Safety findings [5]:

Outcome	Tirzepatide	Dulaglutide
Any gastrointestinal adverse event	42.5%	35.9%
Nausea	25.1%	22.4%
Diarrhea	24.8%	19.1%
Constipation	13%	—
Severe hypoglycemia	0.7%	0.7%
Adjudicated acute pancreatitis	0.6%	0.6%
Investigator-reported acute kidney injury	3.4%	2.7%
Discontinued for adverse events	13.3%	10.2%
Serious adverse events	~32%	~32%

Two medullary thyroid cancers were reported in the tirzepatide group over four years, one of them positive for a RET mutation, the inherited cause of that cancer. None were reported on dulaglutide [5].

All-cause mortality was lower on tirzepatide (hazard ratio 0.84), which the trial authors describe as an exploratory secondary finding rather than a result to bank on [5].

The important caveat: this compares tirzepatide to an older GLP-1 drug, not to nothing. More than 80% of participants were White. Four years is long by trial standards but short compared with how long people expect to take these drugs.

What does the Mounjaro label say about children?

In December 2025 the indication was extended to children aged 10 and older with type 2 diabetes, with a maximum dose of 10 mg once weekly rather than the adult 15 mg [1].

The approval rested on a single 30-week placebo-controlled trial in 99 patients aged 10 to under 18, with a 22-week open-label extension. Side effects during the double-blind period, at placebo / 5 mg / 10 mg [1][6]:

• Vomiting: 3% / 16% / 12%
• Abdominal pain: 9% / 22% / 15%
• Blood glucose under 54 mg/dL when added to basal insulin: 10% / 30% / 27% (on very small numbers, 10 to 11 patients per group)

No severe hypoglycemia was reported. Just under half the children developed antibodies to tirzepatide [1].

Ninety-nine participants is a small safety database, and it is right to read those percentages as coming from a handful of events.

Zepbound has no pediatric indication; its label states that safety and effectiveness in children have not been established [2].

How does the Mounjaro label differ from the Zepbound label?

They are the same molecule, but the two documents are not identical [1][2]:

• Zepbound lists, Mounjaro does not: hair loss, fatigue, dizziness and hypotension as adverse reactions with percentages. Burping, reflux, injection site reactions and hypersensitivity reactions appear on both labels with percentages; on Zepbound they sit in the adverse reaction table, on Mounjaro in the narrative text that follows it.
• Mounjaro lists, Zepbound does not: decreased appetite.
• Mounjaro carries alopecia only in the postmarketing section, meaning spontaneous reports with no reliable frequency.
• Zepbound had a suicidal behavior and ideation warning that its revision history records as removed in February 2026. Mounjaro never carried one.
• Mounjaro carries the cardiovascular risk-reduction indication and a pediatric indication. Zepbound carries the obstructive sleep apnea indication.

None of that means one version of the drug is safer. It means two trial programs in two different populations recorded and reported things differently, and the FDA approved each label against its own data.

What is on European labeling that is not on the US one?

One genuine divergence worth knowing. In December 2024, following a periodic safety review, European regulators concluded that a causal relationship between tirzepatide and both dysesthesia and delayed gastric emptying was at least a reasonable possibility, and required EU product information to be updated [8].

The US label lists dysesthesia as an adverse reaction with percentages, but it does not list delayed gastric emptying as an adverse reaction at all — it appears only in the pharmacology section as part of how the drug works [1].

The short version

Mounjaro’s common side effects are digestive, dose-related and heavily concentrated in the escalation weeks. The percentages on the Mounjaro label are lower than Zepbound’s, but the label itself warns that rates from different trials cannot be compared directly, and the two programs enrolled very different people.

The serious warnings are a boxed thyroid warning resting on rat data of unknown human relevance, a pancreatitis warning that trials have not confirmed as a numerical signal, a gallbladder signal that meta-analyses do support, a kidney warning that is really about dehydration, and a hypoglycemia warning that only really bites when Mounjaro is combined with insulin or a sulfonylurea.

Anything you are experiencing that is not in these tables is worth raising with a healthcare provider rather than researching further.

Sources

1. MOUNJARO (tirzepatide) prescribing information, revised 8/2026 — DailyMed
2. ZEPBOUND (tirzepatide) prescribing information, revised 8/2026 — DailyMed
3. FDA approved Mounjaro label, supplements s044 and s045 (2026)
4. FDA approval letter, Mounjaro supplements s044 and s045
5. SURPASS-CVOT, New England Journal of Medicine
6. SURPASS-PEDS (NCT05260021), ClinicalTrials.gov
7. MHRA Drug Safety Update: strengthened warnings on acute pancreatitis, January 2026
8. CHMP scientific conclusions, tirzepatide periodic safety update, December 2024
9. MHRA updates guidance for GLP-1 prescribers and patients