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Mounjaro side effects and how to avoid them

Mounjaro side effects include GI side effects, rapid heart rate, injection site reactions, and increased pancreatic enzymes
Keith Gardner, RPh, medical writer and reviewer for SingleCare
By | Updated on Nov. 12, 2024
Rx injection pen: Mounjaro side effects and how to avoid them

Key takeaways

  • Mounjaro (tirzepatide) is FDA-approved to treat Type 2 diabetes in adults over 18. The injectable medication improves blood sugar levels by affecting glucose absorption, digestion speed, and insulin release.

  • Common side effects of Mounjaro include gastrointestinal issues, increased heart rate, injection site reactions, and elevated pancreatic enzymes. GI side effects are the most prevalent during dose adjustments.

  • Serious side effects may occur, such as severe stomach problems, risk of thyroid cancer, pancreatitis, hypoglycemia, serious allergic reactions, acute kidney injury, and changes in vision. In severe cases, discontinuation may be necessary.

  • Discuss your health history with a healthcare provider, use Mounjaro as directed at the same time each week, and manage side effects like nausea and hypoglycemia following specific recommendations.

In this article:

Mounjaro (tirzepatide) is approved by the U.S. Food and Drug Administration (FDA) for adults 18 years and older to treat Type 2 diabetes mellitus as an adjunct to diet and exercise. Mounjaro is a prescription-only injectable drug in a class of medicines known as glucagon-like peptide-1 (GLP-1) receptor agonists. The following information highlights potential Mounjaro side effects and how to avoid them.

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Common side effects of Mounjaro

The most common side effects of Mounjaro are gastrointestinal (GI) related and include:

  • Nausea
  • Diarrhea
  • Decreased appetite
  • Vomiting
  • Constipation
  • Indigestion
  • Stomach pain
  • Burping
  • Gastroesophageal reflux disease (GERD)

In clinical trials, most nausea, vomiting, and diarrhea events occurred while the dose of Mounjaro was being increased. These events decreased over time.

Additional common side effects may include:

  • Heart rate increase (tachycardia)
  • Injection site reactions
  • Increased blood levels of pancreatic enzymes amylase and lipase

Serious side effects of Mounjaro

Although not common, Mounjaro may cause serious side effects, including:

  • Severe stomach problems 
  • Risk of thyroid cancer 
  • Pancreatitis (inflamed pancreas)
  • Hypoglycemia (low blood sugar) 
  • Serious allergic reactions 
  • Acute kidney injury 
  • Changes in vision
  • Acute gallbladder problems

Severe stomach problems

GI side effects are the most common adverse events associated with the use of Mounjaro. Most GI side effects occur when therapy begins, are mild or moderate in severity, and decrease with continued treatment. GI side effects tend to be dose-dependent, i.e., the higher the strength of the starting dose, the greater the incidence of GI side effects. 

Risk of thyroid cancer

In animal studies, GLP-1 receptor agonists, such as Mounjaro, led to the formation of thyroid tumors in mice and rats. This finding led to all GLP-1 receptor agonists having a mandated “boxed warning,” also called a black box warning, from the FDA. Mounjaro is contraindicated in patients with a personal or family history of medullary thyroid carcinoma (MTC) or in patients with multiple endocrine neoplasia syndrome type 2 (MEN 2). 

Inflammation of the pancreas (pancreatitis)

Acute pancreatitis has been reported in patients treated with GLP-1 receptor agonists, including Mounjaro. The signs and symptoms of pancreatitis include severe pain in the stomach or abdomen (with or without vomiting), and should they occur, Mounjaro should be discontinued, and the healthcare professional should be contacted.

Weight loss

In clinical studies, Mounjaro patients had significant weight loss. At the highest dose of the medication, Mounjaro reduced body weight by an average of 28 pounds. This secondary effect is important for those with Type 2 diabetes, whose excess weight often contributes to worse health outcomes. 

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Low blood sugar (hypoglycemia)

The risk of getting hypoglycemia (low blood sugar levels) may be higher if Mounjaro is combined with another diabetic medicine that may also cause low blood sugar, such as a sulfonylurea or insulin. Signs and symptoms of low blood sugar may include dizziness or light-headedness, sweating, confusion or drowsiness, headache, blurred vision, slurred speech, shakiness, fast heartbeat, anxiety, irritability or mood changes, hunger, weakness, and feeling jittery.

Serious allergic reactions

There have been reports of serious hypersensitivity reactions, including anaphylactic reactions, in people using GLP-1 receptor antagonists, including Mounjaro. Symptoms of a serious allergic reaction include swelling of the face, lips, tongue, or throat, problems breathing or swallowing, severe rash or itching, fainting or feeling dizzy, and rapid heartbeat. Should any of these symptoms occur while taking Mounjaro, a healthcare professional should be notified immediately.

Acute kidney injury

In those people who have existing kidney problems, Moujanro’s possible side effects of diarrhea, nausea, and vomiting may cause a loss of fluids (dehydration), which may cause kidney problems to worsen. Healthcare professionals may need to closely monitor kidney function when patients use Mounjaro if they experience severe GI side effects leading to dehydration.

Changes in vision

People with diabetes may develop an eye condition called diabetic retinopathy. Those treated with GLP-1 agonists, including Mounjaro, with a history of diabetic retinopathy reported increased symptoms including: spots in vision, a dark area in central vision, trouble seeing at night, colors looking faded or washed out, and vision changes from blurry to clear. Should any of these symptoms occur a healthcare professional should be contacted.

How soon do Mounjaro side effects start?

Many of the most commonly experienced GI side effects of Mounjaro occur when initiating treatment: nausea, diarrhea, decreased appetite, vomiting, constipation, dyspepsia, and abdominal pain. These symptoms may worsen during the first few weeks or months, as the dose is increased, but should begin to lessen once the optimal dose is established. Less common, but more serious side effects, such as severe stomach problems, development of thyroid tumors, or pancreatitis, are typically delayed and may take months or years of drug use to occur.

How long do Mounjaro side effects last?

Common side effects typically go away within a few days or weeks after initiating therapy, or following dose adjustments, or once the body has adjusted to the medicine. Injection site reactions can be minimized by routinely changing the location of the injections. More serious side effects, such as kidney problems, thyroid tumors, or pancreatitis, will likely require the discontinuation of Mounjaro.   

Mounjaro contraindications and warnings

Restrictions

Mounjaro should not be used with any of the following conditions:

  • Type 1 diabetes
  • Younger than 18 years of age
  • Personal or family history of medullary thyroid carcinoma (MTC)
  • History of multiple endocrine neoplasia syndrome type 2 (MEN 2)
  • Allergic to any ingredients in Mounjaro

Overdose

In the event of an overdose, notify the healthcare professional or Poison Control Center. A few days of observation and treatment for symptoms such as nausea and vomiting or mild hypoglycemia may be necessary due to the half-life of Mounjaro of approximately 5 days.

Pregnancy and breastfeeding

There is limited data regarding the use of Mounjaro in pregnant or breastfeeding women. Mounjaro should only be used if the potential benefit justifies the potential risk. A woman’s healthcare provider is the best source of medical advice when managing Mounjaro and other diabetes treatments while pregnant or breastfeeding.

Abuse and dependence

Mounjaro is not habit-forming or addictive. However abrupt discontinuation may result in high blood sugar levels. Always consult with a healthcare professional before discontinuing Mounjaro or switching to another diabetes medicine.

Mounjaro drug interactions

Mounjaro may affect the rate of absorption of other oral medications. This may be important for those drugs where small differences in absorption and blood levels can have an impact on their effectiveness. When taking other medicines to treat diabetes, there is an increased risk of hypoglycemia. Birth control pills taken by mouth may not work as well while using Mounjaro.  It is important to discuss other prescription medicines or over-the-counter drugs, vitamins, or herbal supplements a person takes with a healthcare professional.

How to avoid Mounjaro side effects

Talk to a doctor about your health history

Discuss the following with your healthcare provider before beginning Mounjaro therapy:

  • Do you have any other medical conditions, such as problems with your pancreas, kidneys, liver, or stomach, or have a history of diabetic retinopathy (vision problems related to diabetes)?
  • Do you have GI problems, such as slowed gastric emptying or problems with digesting food?
  • Do you take any other diabetes medications, e.g., insulin or sulfonylureas?
  •  Do you take any other prescription drugs or over-the-counter drugs, vitamins, or herbs?
  • Are you pregnant or plan to become pregnant?
  • Are you breastfeeding or planning to breastfeed?

How to treat side effects of Mounjaro

GI side effects are the most common side effects of Mounjaro, particularly when initiating therapy or adjusting the dose. If you experience nausea:

  • Eat four or more smaller meals instead of three meals a day
  • Stop eating when you feel full
  • Eat bland foods and avoid fried or fatty foods

If you experience hypoglycemia (low blood sugar), eat or drink something with a high sugar content, such as a non-diet soda, fruit juice, or hard candy. Your healthcare provider may prescribe a glucagon injection kit that may be used for severe hypoglycemia.

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