Mounjaro and Zepbound (Tirzepatide) Side Effects by Dose

The most common side effects of tirzepatide, sold as Mounjaro and Zepbound, are digestive: nausea, diarrhea, vomiting and constipation^[1,2]. In the Zepbound weight-management trials, some digestive side effect affected 56% of people on each dose (5, 10 and 15 mg), versus 30% on placebo^[1]. Most were mild or moderate^[3], and the labels say most nausea, vomiting and diarrhea happened while the dose was being stepped up and decreased over time^[1,2]. Pancreatitis and gallbladder problems are less common but serious, and a few signs mean calling your doctor right away.Dotted underline: a drug-label fact; hover over it to see the date it was checked.

I built this page from the current US prescribing information for Zepbound (weight management and obstructive sleep apnea) and Mounjaro (type 2 diabetes), plus the EU Mounjaro label where it adds per-dose detail. Both brands are the same medicine, tirzepatide^[1,2]. Figures with a dotted underline are label facts, checked on October 5, 2026. My tirzepatide guide covers the medicine as a whole.

Zepbound side effects by dose: the weight-management trials

The most detailed table by dose is in the Zepbound label. It pools two 72-week placebo-controlled trials: SURMOUNT-1, in 2,539 adults with obesity or overweight and without type 2 diabetes, and SURMOUNT-2, in 938 adults with type 2 diabetes^[1,7,8]. Each person was assigned to one fixed dose, reached through an escalation period of up to 20 weeks^[1]. SURMOUNT-2 tested only 10 and 15 mg, so the 5 mg column comes from SURMOUNT-1 alone^[1].

Table 1. Zepbound, SURMOUNT-1 and -2 pooled (% of people with at least one episode)

Source: Zepbound label, Table 1, and the text of sections 5.2 and 6.1^[1]. The table lists side effects reported in at least 2% of people on tirzepatide and more often than on placebo.

There’s no 2.5 mg column because, in the label’s words, the 2.5 mg dosage is for treatment initiation and is not approved as a maintenance dosage^[1]. Everyone in the trials passed through it on the way to their assigned dose, so its side effects are folded into the other columns.

The EU label gives SURMOUNT-1 on its own, with one decimal: nausea in 24.6%, 33.3% and 31.0% on 5, 10 and 15 mg, versus 9.5% on placebo, and diarrhea in 18.7%, 21.2% and 23.0%, versus 7.3%^[3]. In that trial, digestive side effects as a whole affected 55.6%, 60.8% and 59.2%, versus 30.3%, and 1.9%, 4.4% and 4.1% stopped treatment because of them, versus 0.5%^[3].

Two later trials add a different angle. In SURMOUNT-3, where people first lost weight with an intensive lifestyle program, 10% on Zepbound and 2% on placebo stopped because of side effects^[1]. In SURMOUNT-4, 7% stopped Zepbound because of side effects during the 36-week open-label lead-in^[1]. In the sleep apnea trials, at 10 or 15 mg, side effects were similar to those in SURMOUNT-1 and -2^[1]. What those trials showed on sleep apnea is in Zepbound for sleep apnea.

These figures can’t be compared with Wegovy’s: the Zepbound label warns that rates from one drug’s trials cannot be directly compared to rates in another drug’s trials^[1].

Mounjaro side effects by dose: type 2 diabetes

The Mounjaro label pools two placebo-controlled trials in adults with type 2 diabetes: SURPASS-1 (tirzepatide alone) and SURPASS-5 (added to basal insulin, with or without metformin). 718 adults took tirzepatide, for an average of 36.6 weeks^[2].

Table 2. Mounjaro, SURPASS-1 and -5 pooled (% of people with at least one episode)

Source: Mounjaro label, Table 1 (side effects in at least 5% of people on tirzepatide), and the text of sections 5.6 and 6.1 (burping to bloating, and the bold rows)^[2].

The EU label gives the same pool with one decimal, nausea in 12.2%, 15.4% and 18.3%, versus 4.3%, and diarrhea in 11.8%, 13.3% and 16.2%, versus 8.9%, and rates them mostly mild (74%) or moderate (23.3%)^[3]. Other figures from the same US pool: allergic reactions in 3.2% versus 1.7%, and injection site reactions in 3.2% versus 0.4%^[2].

Low blood sugar, by dose

The risk specific to diabetes is low blood sugar (hypoglycemia), mainly when tirzepatide is combined with insulin or a sulfonylurea^[2]. The Mounjaro label reports blood sugar below 54 mg/dL by dose:

• Tirzepatide alone (SURPASS-1, 40 weeks): 0% on each dose, versus 1% on placebo, with no severe episodes^[2].
• Added to basal insulin (SURPASS-5, 40 weeks): 16%, 19% and 14% on 5, 10 and 15 mg, versus 13% on placebo; severe episodes in 0%, 2% and 1%, versus 0%^[2]. Severe means needing another person’s help to treat it^[2].
• With a sulfonylurea (a trial of up to 104 weeks): 13.8%, 9.9% and 12.8%; severe in 0.5%, 0% and 0.6%^[2].

The Zepbound label reports it for people with type 2 diabetes in SURMOUNT-2: 4.2% versus 1.3% on placebo, and 10.3% among those also taking a sulfonylurea versus 2.1% among those who weren’t^[1]. In SURMOUNT-1, without diabetes, blood sugar below 54 mg/dL was reported in 0.3% versus none on placebo, though it wasn’t systematically tracked^[1]. The labels say the risk may be lowered by reducing the dose of insulin or the sulfonylurea^[1,2]; that adjustment is your prescriber’s call.

Do higher doses mean more side effects?

It depends on the population and the symptom:

• Weight management (Zepbound): any digestive side effect stayed at 56%, but vomiting and diarrhea rose with the dose while constipation fell, and severe digestive side effects and discontinuations climbed (Table 1)^[1].
• Type 2 diabetes (Mounjaro): digestive side effects, and discontinuations because of them, rose with the dose (Table 2)^[2].
• Heart rate: in type 2 diabetes, episodes of fast heart rate (sinus tachycardia) were reported in 4.6%, 5.9% and 10% on 5, 10 and 15 mg, versus 4.3% on placebo^[2]. In its weight-management trial in people without diabetes (SURMOUNT-1), the EU label reports a heart rate more than 20 beats per minute above baseline at 2 or more visits in a row in 2.4%, 4.9% and 6.3%, versus 1.2%^[3].

What these figures don’t show is which dose suits a given person: in the trials the dose was assigned at random, not adjusted. Your dose and any change to it are decisions for your prescriber.

Side effects in children (Mounjaro)

Mounjaro is approved for type 2 diabetes from age 10; Zepbound’s safety and effectiveness have not been established in children^[1,2]. In the pediatric trial, SURPASS-PEDS, 97 young people aged 10 and older took tirzepatide for an average of 39.9 weeks^[2]. Side effects were like those in adults, except for more vomiting, abdominal pain and low blood sugar^[2].

Source: Mounjaro label, section 6.1^[2]. Blood sugar below 54 mg/dL (Table 3) was reported in 9% on each dose versus 4% on placebo when added to metformin alone, with about 22 to 24 children per group^[2]. Added to basal insulin, the figures were 30% and 27% versus 10%, but those groups had only 10 or 11 children each, so they rest on a handful of cases^[2]. No severe low blood sugar episodes were reported^[2].

Less common but serious side effects

These come from sections 5 and 6 of the US labels. Zepbound figures are from SURMOUNT-1 and -2; Mounjaro figures from its placebo-controlled diabetes trials^[1,2].

• Acute pancreatitis. Confirmed in 0.2% on Zepbound and 0.2% on placebo in the weight trials^[1]. Across the diabetes trials, 0.23 patients per 100 years of exposure on tirzepatide versus 0.11 on comparators^[2]. In the sleep apnea trials, 0.84 per 100 years on Zepbound versus 0 on placebo^[1]. If pancreatitis is suspected, the labels tell prescribers to stop the medicine and start appropriate management^[1,2].
• Gallbladder. On Zepbound, gallstones in 1.1% versus 1%, gallbladder inflammation (cholecystitis) in 0.7% versus 0.2%, and gallbladder removal in 0.2% versus none; these events were associated with weight reduction^[1]. On Mounjaro, acute gallbladder disease in 0.6% versus 0%^[2].
• Dehydration and kidneys. On Zepbound, acute kidney injury in 0.5% versus 0.2%^[1]. After approval there have been reports of acute kidney injury, sometimes requiring dialysis, mostly in people whose nausea, vomiting or diarrhea led to dehydration^[1,2].
• Low blood pressure. On Zepbound, 1.6% versus 0.1%; 2.2% in people also taking blood pressure medicine versus 1.2% in those who weren’t^[1]. The label adds that it also occurred along with digestive side effects and dehydration^[1].
• Heart rate. Mean increases of 1 to 3 beats per minute on Zepbound, versus no increase on placebo^[1], and 2 to 4 on Mounjaro, versus 1^[2]. The Mounjaro label calls the clinical relevance of heart rate increases uncertain^[2].
• Allergic reactions. On Zepbound, severe allergic reactions in 0.1% versus none; immediate reactions (within a day of the injection) in 2.1% versus 0.4%; most were skin reactions such as rash or itching^[1].
• Injection site reactions. On Zepbound they were more frequent in people who developed antibodies to tirzepatide (11.3%) than in those who didn’t (1%)^[1].
• Dysesthesia (altered skin sensation, such as tingling or burning). On Zepbound, 0.2%, 0.2% and 0.4% on 5, 10 and 15 mg, versus 0.1%^[1]; on Mounjaro, 0.4% on each dose, versus none^[2].
• Taste and mouth. On Zepbound, altered taste (dysgeusia) in 0.4% versus none, and dry mouth or throat in 1% versus 0.1%^[1].
• Pancreatic enzymes. Zepbound raised amylase by 20% to 25% and lipase by 28% to 35% on average; the label says their clinical significance is unknown without other signs of pancreatitis^[1].
• Anesthesia and sedation. The labels report rare cases of pulmonary aspiration (stomach contents getting into the lungs) in people on GLP-1 medicines having general anesthesia or deep sedation, despite fasting as instructed^[1,2].
• Thyroid and eyes. Both US labels carry a boxed warning about thyroid C-cell tumors in rats, and a warning on diabetic retinopathy in type 2 diabetes^[1,2]; both are covered in the FAQ below.

What has been reported since approval

Section 6.2 of both US labels lists reports received after the medicine went on the market: acute pancreatitis, including hemorrhagic and necrotizing pancreatitis sometimes resulting in death; ileus and intestinal obstruction; severe constipation, including fecal impaction; anaphylaxis and angioedema; and acute kidney failure or worsening of chronic kidney failure, sometimes requiring dialysis^[1,2]. The Mounjaro label adds hair loss (alopecia)^[2]. Because these reports are voluntary, it’s not always possible to estimate their frequency or establish that the drug caused them^[1,2].

If constipation comes with pain, a swollen belly or vomiting, don’t wait it out: call your doctor.

What regulators have reviewed

• EMA, December 2024. After a periodic safety review, the EMA’s safety committee (PRAC) judged a causal link between tirzepatide and dysesthesia, and delayed gastric emptying, at least a reasonable possibility. The committee for human medicines (CHMP) agreed: both were added to the EU label, and the benefit-risk balance was unchanged^[10].
• EMA, April 2024. The PRAC concluded that the evidence doesn’t support a causal link between GLP-1 receptor agonists and suicidal thoughts or actions. Tirzepatide wasn’t part of that review^[11].
• FDA, January 13, 2026. The FDA asked for the suicidal behavior and ideation warning to be removed from the labels of Zepbound, Wegovy and Saxenda. After analyzing 91 trials with 107,910 people and data from more than 2 million patients, it found no increased risk^[12]. The current Zepbound label lists that warning as removed in February 2026^[1].

Do Mounjaro and Zepbound side effects go away?

For most people, the digestive ones ease. Both US labels say the majority of nausea, vomiting and diarrhea occurred during dose escalation and decreased over time^[1,2], and the EU label says the same^[3]. The Zepbound label adds that most people who stopped because of side effects did so during the first few months, because of digestive side effects^[1]. One reason the start is harder: tirzepatide delays gastric emptying, and the delay is largest after the first dose and diminishes over time^[1].

The pooled analysis of SURMOUNT-1 to -4 adds how often people needed help^[4]:

• In SURMOUNT-1 to -3, 13.8% to 27.5% on tirzepatide used an anti-nausea medicine, versus 5.8% to 6.7% on placebo^[4].
• Across the four trials, 1.0% to 10.5% stopped tirzepatide because of digestive side effects, depending on the trial and dose^[4].

It’s a post hoc analysis, funded by Lilly, and it doesn’t report how long each episode lasted^[4]. No US label does either. How symptoms evolve week by week, and how tirzepatide compares with semaglutide on timing, is in my side effects week-by-week guide.

What tends to help

In the SURMOUNT trials, people with digestive symptoms they couldn’t tolerate were first advised to eat smaller meals, split three daily meals into four or more, and stop eating when they felt full^[4]. The 2025 joint advisory from four US medical and nutrition societies suggests a small breakfast and then small meals every 3 to 4 hours, avoiding fatty or high-fiber foods in the first few days, and adding fiber gradually^[5]. It notes that alcohol can worsen nausea and reflux, and that anti-nausea medicines can help during dose increases, though some can worsen constipation^[5]. Ask your prescriber or pharmacist before taking any.

By symptom, I go into detail in:

• Nausea on GLP-1 medications: what to eat
• Diarrhea on GLP-1 medications
• Constipation on GLP-1 medications
• Acid reflux on GLP-1 medications
• Hydration on GLP-1 medications: the Medication Guides say it is important to drink fluids to help reduce your chance of dehydration^[1,2]
• Injection site reactions: the labels ask you to rotate the injection site with each weekly injection^[1,2]

To bring real data to your appointment, my printable symptom diary logs symptoms day by day for 4 weeks, and the doctor-visit checklist has side-effect questions ready to print.

What’s known about long-term side effects

Two sources go beyond three years:

• SURMOUNT-1 at 3 years. 1,032 people with obesity and prediabetes stayed on their dose for 176 weeks, then were followed for 17 weeks off treatment. The most common side effects were digestive, mostly mild to moderate and concentrated in the first 20 weeks, and the authors found no new safety signals. Lilly funded the trial^[6].
• SURPASS-CVOT. This trial compared tirzepatide with dulaglutide in 13,299 adults with type 2 diabetes and established cardiovascular disease, with a median follow-up of 210.1 weeks, about 4 years^[2,9]. In the 6,647 adults on tirzepatide, side effects were similar except for dysesthesia (0.7%), decreased appetite (17%), constipation (13%), vomiting (12%), abdominal pain (10%) and fatigue (10%)^[2]. The EU label reports a maximum mean heart rate increase of 6 beats per minute in that trial^[3].

What isn’t known: effects beyond about 4 years, since no label has longer controlled data than SURPASS-CVOT^[2,3], and how far trial rates carry over to everyday use. In both labels’ words, they may not reflect the rates observed in practice^[1,2].

When to call your doctor

You can report any side effect to the FDA’s MedWatch program at 1-800-FDA-1088, as the labels note^[1,2].

Frequently asked questions

Does Mounjaro or Zepbound cause hair loss?

It’s a common side effect in the Zepbound label: 5%, 4% and 5% on 5, 10 and 15 mg, versus 1% on placebo^[1]. The label links it to weight reduction and reports it more often in women (7.1%) than in men (0.5%); on placebo, 1.3% of women and no men^[1]. No one on Zepbound stopped treatment because of it^[1]. The Mounjaro label lists hair loss only among reports after approval^[2]. More in hair loss on GLP-1 medications.

Does Mounjaro have sexual side effects?

Neither US label lists sexual side effects^[1,2]. On birth control, the US labels say tirzepatide may make birth control pills by mouth less effective, and advise switching to a non-oral method or adding a barrier method for 4 weeks after starting and for 4 weeks after each dose increase^[1,2]. The EU label, by contrast, doesn’t consider the drop in pill levels after a single dose of tirzepatide clinically relevant^[3]. Talk it through with your prescriber; I cover cycle changes in period changes on Ozempic or Mounjaro.

Does having nausea mean it’s working better?

No. In the pooled SURMOUNT analysis, weight loss was similar in people with and without nausea, and nausea, vomiting, diarrhea and indigestion together were associated with at most 3.1% of the total weight lost^[4]. What to expect on average is in how much weight you can lose on GLP-1 medications.

Are Mounjaro and Zepbound side effects the same?

It’s the same medicine with the same warnings, but each label has its own trials: Mounjaro’s in type 2 diabetes, Zepbound’s in weight management, and the rates differ for that reason^[1,2]. I set them side by side in Mounjaro vs. Zepbound.

Can Mounjaro cause suicidal thoughts?

In January 2026, the FDA concluded that the data don’t show an increased risk, and the warning is no longer in the Zepbound label^[1,12]. The 2024 EU review didn’t include tirzepatide^[11]. If you’re thinking of harming yourself, get help now: in the US, call or text 988, the Suicide & Crisis Lifeline.

Does Mounjaro affect your eyes?

Neither the US labels nor the EU label list optic nerve damage (NAION) for tirzepatide^[1,2,3]. In type 2 diabetes, temporary worsening of diabetic retinopathy has been reported with rapid improvement in glucose control, so the labels ask for monitoring in people who already have retinopathy^[1,2].

Does tirzepatide cause thyroid cancer?

It isn’t known. Both US labels carry a boxed warning because tirzepatide caused thyroid C-cell tumors in rats, and it’s unknown whether it causes them, including medullary thyroid carcinoma (MTC), in humans^[1,2]. In the US, it’s contraindicated in people with a personal or family history of MTC or with MEN 2, an inherited syndrome^[1,2]. The EU label describes the same rat tumors, of unknown relevance to humans, but its only contraindication is hypersensitivity^[3]; my tirzepatide guide has the details.