Mounjaro Side Effects: what the label lists, by dose, and when to get help

Key takeaways

• Nausea is the most common Mounjaro side effect: 12% to 18% depending on dose vs 4% on placebo in adults with type 2 diabetes.^[1]
• Digestive side effects mostly happened during dose increases and decreased over time; 3.0% to 6.6% stopped because of them vs 0.4% on placebo.^[1]
• Low blood sugar was rare with Mounjaro alone but occurred in 14% to 19% when added to basal insulin (13% on placebo).^[1]
• Mounjaro may make birth-control pills less effective; the label advises a non-oral or backup method for 4 weeks after starting and after each dose increase.^[1]
• Serious risks include pancreatitis, kidney injury from dehydration, gallbladder disease and allergic reactions; there is a boxed warning about thyroid tumors in rats.^[1]

In short: The most common side effects of Mounjaro (tirzepatide) are nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion and stomach pain. In the label’s placebo-controlled trials in adults with type 2 diabetes, nausea affected 12% to 18% depending on the dose (vs 4% on placebo), mostly while the dose was being increased, and digestive side effects decreased over time. Serious risks include pancreatitis, low blood sugar with insulin or sulfonylureas, kidney injury from dehydration and severe allergic reactions, and Mounjaro has a boxed warning about thyroid C-cell tumors seen in rats (label checked on 2026-10-06).

This page explains what the official Mounjaro prescribing information and Medication Guide say about side effects: how often each happened at each dose, what changes in children 10 and older, how low blood sugar risk depends on other diabetes medicines, the birth-control caution, and which symptoms need urgent care. It is general information, not medical advice. Talk with your prescriber before changing or stopping any medicine.

Where these numbers come from

Mounjaro is FDA approved to improve blood sugar in adults and children 10 and older with type 2 diabetes, and to reduce the risk of heart attack, stroke and cardiovascular death in adults with type 2 diabetes at high cardiovascular risk. It is not approved for weight management; the same medicine, tirzepatide, is sold for weight as Zepbound. The main side-effect table on the Mounjaro label pools two placebo-controlled trials (SURPASS-1, Mounjaro alone, and SURPASS-5, added to basal insulin) with 718 adults on Mounjaro for an average of about 37 weeks. A larger pool of seven trials with 5,119 adults showed similar types and rates. The Zepbound label, from trials in people with obesity, reports higher rates of some digestive effects; see Zepbound side effects.

The most common side effects, by dose

• 5 mg
• 10 mg
• 15 mg
• Placebo

Nausea12%15%18%4%

Diarrhea12%13%17%9%

Decreased appetite5%10%11%1%

Vomiting5%5%9%2%

Constipation6%6%7%1%

Indigestion (dyspepsia)8%8%5%3%

Abdominal pain6%5%5%4%

Most common Mounjaro side effects by dose vs placebo (adults with type 2 diabetes)

Item	5 mg	10 mg	15 mg	Placebo
Nausea	12%	15%	18%	4%
Diarrhea	12%	13%	17%	9%
Decreased appetite	5%	10%	11%	1%
Vomiting	5%	5%	9%	2%
Constipation	6%	6%	7%	1%
Indigestion (dyspepsia)	8%	8%	5%	3%
Abdominal pain	6%	5%	5%	4%

SURPASS-1 and SURPASS-5 pooled: 237 on 5 mg, 240 on 10 mg, 241 on 15 mg, 235 on placebo.

Source: Mounjaro prescribing information, Table 1 (checked on October 6, 2026)

Digestive side effects overall occurred in 37.1%, 39.6% and 43.6% of people on 5, 10 and 15 mg vs 20.4% on placebo. Smaller digestive effects reported more often than with placebo were burping (2.5% to 3.3% vs 0.4%), gas (1.3% to 2.9% vs 0%), acid reflux (1.7% to 2.5% vs 0.4%) and bloating (0.4% to 2.9% vs 0.4%). In the heart-outcomes trial, where 6,647 adults with heart disease took Mounjaro, side effects were similar except that decreased appetite (17%), constipation (13%), vomiting (12%), stomach pain (10%), fatigue (10%) and dysesthesia (0.7%) were reported more often than in the pooled trials.

When they tend to happen

The label says most reports of nausea, vomiting and diarrhea occurred during dose escalation and decreased over time. Mounjaro starts at a low dose and, if more blood-sugar control is needed, is increased in steps of at least 4 weeks; the label says following this schedule reduces the risk of digestive side effects. Stopping because of digestive side effects rose with dose: 3.0%, 5.4% and 6.6% vs 0.4% on placebo. Your prescriber sets the pace and decides what to do if side effects are bothersome.

The Medication Guide says diarrhea, nausea and vomiting can cause dehydration, which may lead to kidney problems, and that drinking fluids helps reduce that chance; tell your provider right away about symptoms that do not go away. For food approaches people discuss with their care team, see our GLP-1 diet page.

Low blood sugar (hypoglycemia)

Used alone, Mounjaro did not cause readings below 54 mg/dL in the 40-week trial (0% at every dose vs 1% on placebo), and no severe episodes occurred. Added to basal insulin, readings below 54 mg/dL occurred in 16%, 19% and 14% of people on 5, 10 and 15 mg vs 13% on placebo, with severe episodes in 2% (10 mg) and 1% (15 mg). With a sulfonylurea, in a trial of up to 104 weeks, low blood sugar occurred in 13.8%, 9.9% and 12.8%, and severe episodes in 0.5%, 0% and 0.6%.

• 5 mg
• 10 mg
• 15 mg
• Placebo

Mounjaro alone (40 weeks)0%0%0%1%

Added to basal insulin (40 weeks)16%19%14%13%

Low blood sugar (below 54 mg/dL) with Mounjaro, by other treatment

Item	5 mg	10 mg	15 mg	Placebo
Mounjaro alone (40 weeks)	0%	0%	0%	1%
Added to basal insulin (40 weeks)	16%	19%	14%	13%

About 115-121 adults per group. With a sulfonylurea (separate trial, up to 104 weeks): 13.8%, 9.9% and 12.8%, no placebo group.

Source: Mounjaro prescribing information, Table 2 (checked on October 6, 2026)

Signs of low blood sugar listed in the Medication Guide include dizziness or light-headedness, sweating, confusion or drowsiness, headache, blurred vision, slurred speech, shakiness, a fast heartbeat, anxiety, irritability or mood changes, hunger, weakness and feeling jittery. The label says prescribers may consider lowering the dose of insulin or a sulfonylurea when starting Mounjaro.

Children 10 and older

In SURPASS-PEDS, 99 children and teens 10 and older with type 2 diabetes were randomized (97 received Mounjaro at some point). Side effects were similar to adults except for more vomiting, stomach pain and low blood sugar. During the 30-week placebo-controlled period, vomiting occurred in 16% (5 mg) and 12% (10 mg) vs 3% on placebo, and stomach pain in 22% and 15% vs 9%. Readings below 54 mg/dL occurred in 30% and 27% of those also on basal insulin (vs 10%) and 9% of those on metformin alone (vs 4%); no severe episodes were reported.

Serious side effects and warnings

Boxed warning: thyroid C-cell tumors. In a 2-year study in rats of both sexes, tirzepatide caused thyroid C-cell tumors that increased with dose and duration. It is unknown whether Mounjaro causes these tumors, including medullary thyroid carcinoma (MTC), in people. Mounjaro must not be used by anyone with a personal or family history of MTC or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2). Tell your provider about a neck lump, hoarseness, trouble swallowing or shortness of breath.

• Pancreatitis. 14 confirmed events in 13 people on Mounjaro (0.23 per 100 years of exposure) vs 3 on comparators (0.11). Fatal cases have been reported after approval with this class.
• Kidney injury from dehydration, sometimes needing dialysis, reported after approval.
• Severe digestive reactions in 1.3%, 0.4% and 1.2% vs 0.9%; not recommended in severe gastroparesis. Ileus, bowel obstruction and fecal impaction have been reported after approval.
• Gallbladder disease (gallstones, biliary colic, gallbladder removal) in 0.6% vs 0%.
• Allergic reactions in 3.2% vs 1.7%, sometimes severe (for example hives and eczema); anaphylaxis and angioedema have been reported after approval.
• Diabetic eye complications can temporarily worsen with rapid improvement in blood sugar in people with a history of retinopathy.
• Aspiration during anesthesia or deep sedation: tell procedure teams you take Mounjaro.
• Never share a KwikPen, even with a new needle.

Placebo4.3%

Mounjaro 5 mg4.6%

Mounjaro 10 mg5.9%

Mounjaro 15 mg10%

Heart rate: episodes of fast heartbeat (sinus tachycardia with a rise of 15 bpm or more)

Item	Value
Placebo	4.3%
Mounjaro 5 mg	4.6%
Mounjaro 10 mg	5.9%
Mounjaro 15 mg	10%

Placebo-controlled trials in adults. Average resting heart rate rose 2 to 4 beats per minute (1 on placebo). The label says the clinical relevance is uncertain.

Source: Mounjaro prescribing information, section 6.1 (checked on October 6, 2026)

Other effects people ask about

Injection-site reactions were reported in 3.2% vs 0.4%, more often in people who developed antibodies to tirzepatide. Hair loss (alopecia) is listed among reports received after approval, where frequency cannot be reliably estimated. Dysesthesia (unusual skin sensations) occurred in 0.4% at each dose in the pooled trials and 0.7% in the heart-outcomes trial; taste changes in 0.1%. Pancreatic enzymes rose on average (amylase 33% to 38%, lipase 31% to 42%); the label says the meaning is unknown without other signs of pancreatitis. Weight loss on Mounjaro can include some lean mass; see muscle loss on GLP-1s and the Ozempic face guide for changes in appearance after weight loss.

Mood. The FDA reported on January 13, 2026 that its review of 91 trials with 107,910 participants found no increased risk of suicidal thoughts or behavior with GLP-1 medicines; labels of GLP-1 medicines approved for type 2 diabetes did not include that warning. Talk to your clinician about any new or worsening depression; in a crisis, call or text 988.

Birth control, pregnancy and breastfeeding

The label says data in pregnancy are insufficient, that animal studies suggest possible risk to the fetus, and that Mounjaro should be used in pregnancy only if the potential benefit justifies the potential risk; poorly controlled diabetes in pregnancy also carries risks, so planning with your diabetes and obstetric clinicians matters. In a small single-dose study, tirzepatide was undetectable or very low in breast milk; effects on a breastfed infant are unknown.

Who may be at higher risk

• People on insulin or a sulfonylurea (low blood sugar), and children on basal insulin.
• People using birth-control pills.
• People with a history of diabetic retinopathy or pancreatitis.
• Anyone who becomes dehydrated, especially with kidney disease.
• People taking medicines that need precise blood levels, such as warfarin (closer monitoring).
• Anyone with severe gastroparesis or a personal or family history of MTC or MEN 2.

Compounded products, reporting and cost

Compounded tirzepatide is not FDA approved; the FDA has reported fraudulent compounded tirzepatide and adverse events with doses beyond the approved label (see compounded GLP-1s). Report suspected side effects to Eli Lilly at 1-800-545-5979 or to the FDA at 1-800-FDA-1088. On 2026-10-06, Lilly’s savings card offered Mounjaro for as little as $25 for up to a 3-month prescription with commercial coverage, or as low as $499 a month with commercial insurance that does not cover it (government beneficiaries excluded from the $25 offer; card expires December 31, 2026). See the cost hub and the GLP-1 cost comparison tool. For the whole class, see our GLP-1 side effects guide, Ozempic side effects and semaglutide vs tirzepatide.

Questions to ask your doctor or pharmacist

• Which side effects should I expect at my dose, and when should I call you?
• Should my insulin or sulfonylurea dose be lowered when I start Mounjaro?
• What birth-control method should I use at the start and after each increase?
• Do I need eye checks because of diabetic retinopathy?
• How should I prepare for surgery or a procedure with sedation?

Frequently asked questions

What are the most common side effects of Mounjaro?

Nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion and stomach pain. Nausea affected 12% to 18% depending on dose vs 4% on placebo in the label's adult trials.

Do Mounjaro side effects go away?

The label says most nausea, vomiting and diarrhea occurred during dose escalation and decreased over time. Tell your prescriber about symptoms that persist or are severe.

Does Mounjaro cause low blood sugar?

Rarely on its own. With basal insulin, readings below 54 mg/dL occurred in 14% to 19% vs 13% on placebo, and with a sulfonylurea in about 10% to 14%. Your prescriber may lower those medicines.

Is Mounjaro the same as Zepbound?

Both contain tirzepatide. Mounjaro is approved for type 2 diabetes; Zepbound is approved for weight management and sleep apnea with obesity. The side-effect rates on each label come from different trials.

Does Mounjaro affect birth control pills?

It may make them less effective. The label advises switching to a non-oral method or adding a barrier method for 4 weeks after starting and after each dose increase.

Can Mounjaro cause pancreatitis?

Yes, it has occurred: 0.23 patients per 100 years of exposure on Mounjaro vs 0.11 on comparators in trials. Stop and call your provider for severe stomach pain that will not go away.

Does Mounjaro cause hair loss?

Hair loss (alopecia) is listed among reports received after approval, where frequency cannot be reliably estimated.

Are side effects different in children?

In children 10 and older with type 2 diabetes, side effects were similar to adults except for more vomiting, stomach pain and low blood sugar.

Does Mounjaro raise heart rate?

Average resting heart rate rose 2 to 4 beats per minute. Episodes of fast heartbeat with a rise of 15 or more occurred in 10% on 15 mg vs 4.3% on placebo; the label says the clinical relevance is uncertain.

Official sources

• Prescribing information (FDA label)
• FDA approval letter or page
• Manufacturer information

References

1. MOUNJARO (tirzepatide) injection: prescribing information. Eli Lilly and Company, via DailyMed, 2026. (accessed October 7, 2026) Drug label
2. FDA requests removal of suicidal behavior and ideation warning from GLP-1 receptor agonist medications. U.S. Food and Drug Administration, 2026. (accessed October 6, 2026) Government page
3. FDA’s concerns with unapproved GLP-1 drugs used for weight loss. U.S. Food and Drug Administration, 2026. (accessed October 7, 2026) Government page
4. Mounjaro savings and resources. Eli Lilly and Company. (accessed October 7, 2026) Other
5. Drugs@FDA: Mounjaro, NDA 215866, approval history. U.S. Food and Drug Administration. (accessed October 6, 2026) Government page
6. Frias JP, Davies MJ, Rosenstock J, et al.. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes (SURPASS-2). New England Journal of Medicine, 2021. doi:10.1056/NEJMoa2107519 · PMID 34170647 · NCT03987919 (accessed October 7, 2026) Randomized trial
7. Nicholls SJ, Pavo I, Bhatt DL, et al.. Cardiovascular Outcomes with Tirzepatide versus Dulaglutide in Type 2 Diabetes (SURPASS-CVOT). New England Journal of Medicine, 2025. doi:10.1056/NEJMoa2505928 · PMID 41406444 · NCT04255433 (accessed October 6, 2026) Randomized trial
8. Medicare GLP-1 Bridge: information for providers. Centers for Medicare and Medicaid Services. (accessed October 7, 2026) Government page

Facts checked on October 6, 2026

Educational information, not medical advice. Talk with a qualified healthcare professional about your own situation. In an emergency call 911.