Mounjaro Side Effects

Common Mounjaro side effects include digestive distress, such as vomiting, diarrhea, constipation and nausea. More severe side effects of Mounjaro include acute organ failure, pancreatitis, diabetic retinopathy and gastroparesis. Animal studies show an increased risk of certain thyroid cancers.

Last Modified: May 21, 2024
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Latest Side Effects Information for Mounjaro

As of the latest update published on Dec. 31, 2023, some of the most common Mounjaro (tirzepatide) side effects reported to the FDA Adverse Events Reporting System (FAERS) were injection site pain, nausea, diarrhea and vomiting.

The top reasons for reporting adverse events were because users accidentally took the wrong dose, took an extra dose or due to off-label use.

FDA Adverse Events Reporting System (FAERS) Data for Mounjaro Side Effects
Total cases reported25,126
Serious cases (including deaths)2,000
Source: FAERS Database
Disclaimer: Reports sent to the FDA don't necessarily mean the drug caused an adverse event. Consult a health care professional before stopping or changing medication.

Possible Mounjaro Side Effects

The most common Mounjaro side effects include nausea, diarrhea, vomiting, constipation, decreased appetite, indigestion and abdominal pain. Less than 5% of patients report experiencing these side effects according to manufacturer Eli Lilly.

“Side effects are pretty similar between different GLP-1s,” Dr. Eldad Einav, cardiologist and obesity specialist at myW8 in Beverly Hills, told Drugwatch. The GLP-1 agonist class includes semaglutide drugs like Ozempic and Wegovy and tirzepatide drugs like Mounjaro and Zepbound.

“[The side effects] are considered a class effect, similar for all this class of medications,” Einav said.

Einav cited the SURPASS-2 trial, which compared tirzepatide and semaglutide head-to-head. It found that Mounjaro showed a slightly higher rate of serious side effects compared to Ozempic.

Possible Mounjaro (tirzepatide) side effects include:
  • Abdominal pain
  • Acute kidney injury
  • Bloating
  • Constipation
  • Decreased appetite
  • Diabetic retinopathy
  • Diarrhea
  • Fast heartbeat
  • Fatigue
  • Flatulence
  • Gallbladder problems
  • Gastroparesis (stomach paralysis)
  • Heartburn
  • Hives
  • Hunger
  • Hypoglycemia
  • Indigestion
  • Injection site reactions
  • Kidney problems
  • Nausea
  • Pancreatitis
  • Risk of thyroid cancer
  • Sweating
  • Thyroid tumors
  • Vision changes

“Switching to a different medication within the same class can sometimes improve tolerability for patients who experience side effects, due to variations in how individuals respond to specific drugs,” Einav said.

If you experience any side effect that persists or bothers you, speak to your health care provider.

Severe Mounjaro Side Effects

In rare cases, Mounjaro may cause severe side effects such as organ failure, low blood sugar, inflammation of the pancreas, diabetic retinopathy and gastroparesis. These conditions can be life-threatening.

Mounjaro Warnings for Severe Side Effects
Acute Gallbladder Disease
A small percentage (0.6%) of individuals taking Mounjaro in clinical trials developed symptoms of acute gallbladder disease.
Acute Kidney Injury
Severe gastrointestinal symptoms associated with Mounjaro use may contribute to dehydration. If it persists, it may cause acute kidney injury.
Diabetic Retinopathy
Mounjaro may contribute to worsening symptoms in some patients with a history of diabetic retinopathy.
Mounjaro contributes to delayed gastric emptying. This may become severe and result in a paralysis of the stomach, which stops emptying altogether.
Hypersensitivity Reactions
Some patients may experience an allergic reaction to tirzepatide. Anaphylaxis is a possible outcome for those with a hypersensitivity to the drug.
Mounjaro may contribute to hypoglycemia when used with insulin or an insulin secretagogue.
Some patients treated with GLP-1 receptor agonists have displayed symptoms of acute pancreatitis.

Patients who experienced severe side effects after taking Mounjaro have filed lawsuits against Eli Lilly. Mounjaro lawsuits claim the drug caused gastroparesis and severe vomiting lasting for weeks despite treatment. They also claim that Eli Lilly failed to adequately warn about these and other possible adverse reactions.

Lawsuit Information
Lawsuits are being filed by people who developed severe gastroparesis after using Mounjaro.
View Lawsuits

Mounjaro Boxed Warning

Since its approval in 2022, the FDA has required Mounjaro’s label to include a boxed warning about the risk of thyroid tumors. Box warnings are the highest warning level the FDA can assign to a drug.

Clinical studies showed an increased risk of thyroid tumors in rats taking tirzepatide, the active ingredient in Mounjaro and its weight-loss sister drug, Zepbound.

“In both sexes of rats, tirzepatide caused a dose-dependent and treatment-duration-dependent increase in the incidence of thyroid C-cell tumors (adenomas and carcinomas) in a 2-year study at clinically relevant plasma exposures. It is unknown whether Mounjaro causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans…”

If you take Mounjaro and experience signs of thyroid tumors — including hoarseness, lumps in the neck and difficulty swallowing — you should immediately report the symptoms to your doctor.

How Long Do Mounjaro Side Effects Last?

Most side effects of taking Mounjaro resolve within several days. Patients are most likely to experience side effects when first starting Mounjaro and after dosage increases. Some side effects may disappear during treatment as your body adjusts to the medicine.

Higher doses contribute to greater chances of side effects and more severe symptoms. Patients have reported long-term side effects from Mounjaro, including vomiting that lasts for weeks. More serious side effects, such as severe digestive issues or pancreatitis, can last long term.

Anyone experiencing such side effects should speak to their doctor immediately.

Is Mounjaro Safe To Take?

Mounjaro is considered safe for most patients who use it to treat Type 2 diabetes. Its FDA approval for this purpose indicates that its benefits outweigh the potential risks.

Even though Mounjaro may be generally safe for weight loss in overweight or obese individuals, it may cause malnutrition or muscle loss in average-weight or underweight individuals. Off-label use may increase risks. Eli Lilly and the experts Drugwatch talked to recommend avoiding Mounjaro for off-label use. Zepbound (tirzepatide), another Eli Lilly product, is FDA-approved for weight loss.

Discuss side effects with a doctor before taking Mounjaro and notify them if you experience any after starting tirzepatide treatment.

Whether prescribed for treating Type 2 diabetes or for weight loss, tirzepatide’s side effects are the same.

How To Manage Mounjaro Side Effects

Your health care provider can advise you on reducing your specific Mounjaro’s side effects. To alleviate gastrointestinal discomfort, limit fatty or spicy foods, eat slowly and stop when full.

5 Tips for Managing Mounjaro Side Effects
  1. Get fresh air regularly.
  2. Eat small meals frequently.
  3. Drink water, herbal teas or other clear liquids to stay hydrated.
  4. Cut down on sugar and high-fat foods.
  5. Avoid strong-smelling meals.

Drinking chamomile tea or ginger ale and taking over-the-counter meds can help to ease nausea. For constipation, eat high-fiber foods and drink lots of fluids.

When To Talk to Your Doctor About Mounjaro Side Effects

If you’re experiencing Mounjaro side effects that last for more than a few days or interfere with your daily activities, it’s essential to talk to your doctor.

Talk to your doctor if you experience any of these severe side effects while taking Mounjaro:
  • Eye-related complications or changes in vision, such as blurred vision.
  • Gallbladder complications, characterized by pale-colored stools, stomach discomfort after eating, nausea, heartburn, bloating and intense upper abdominal pain radiating to the back.
  • Low blood sugar signs, including headaches, hunger pangs, weakness, perspiration, confusion, irritability, dizziness, rapid heartbeat or jitteriness.
  • Renal problems, manifesting as decreased or absent urination, ankle or foot swelling, and feelings of exhaustion or breathlessness.
  • Severe gastrointestinal issues.
  • Symptoms suggestive of a thyroid tumor, such as neck swelling or a lump, difficulty swallowing, hoarseness or breathlessness.

Serious symptoms like difficulty breathing, severe abdominal pain, skin rash and vomiting require immediate medical attention. Even milder symptoms like vomiting and diarrhea can lead to dehydration. Consult your doctor if symptoms last for over a week.

Please seek the advice of a medical professional before making health care decisions.