What Is Mounjaro Used For? What You Need to Know

Mounjaro is a new type of diabetes drug that is also being used for medical weight loss. Learn how it works and its side effects.

Woman injecting herself a new diabetes drug called mounjaro
Sarah Bullard, MS, RD, LD
— Signos
Dietitian and Nutrition Writer
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Updated by

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Science-based and reviewed

May 17, 2024
October 29, 2023
— Updated:
October 30, 2023

Table of Contents

Mounjaro is a brand-name subcutaneous injectable prescription medication used to improve blood sugar levels in adults with type 2 diabetes mellitus alongside diet and exercise.1,2 

It has been more effective than other injectable diabetes medications. Similar medications include Byetta (exenatide), Ozempic (semaglutide) and Trulicity (dulaglutide).2

Consult your healthcare provider about using any diabetes medication. 

In the last 15 years, various injectable medications have been recommended early in diabetes treatment due to their ability to improve fasting and overall blood sugar levels, lower body weight, and have positive heart disease outcomes.2  

In this article, you’ll learn how individuals use Mounjaro, how it aids in weight loss and blood sugar control for people with type 2 diabetes, and its side effects. 

What is Mounjaro?

Mounjaro combines two injectable medications: a glucose-dependent insulinotropic polypeptide (GIP RAs) and a glucagon-like peptide-1 receptor agonist (GLP-1 RAs) made by Eli Lilly and Company.1,2 

Mounjaro is a once-weekly injection. Mounjaro is not insulin. The generic name is tirzepatide. The two medications in Mounjaro work better together than GLP-1 RAs alone. 

Mounjaro comes in a prefilled injection pen. You inject under your skin with or without food. Rotate injection locations to help prevent injection site irritation. You can inject Mounjaro in your stomach, thighs, or the back of your upper arms.1

The clinical trials on Mounjaro exhibit a powerful blood sugar lowering and weight loss ability with side effects similar to existing GLP-1 RAs on the market.2

Mounjaro has undergone phase 1 and 2 clinical trials and is currently in over nine phase 3 clinical trials.2

Phase 1 trials are done for new medications and involve a smaller group of people (20-100). They are done to find the highest safe dose of a new medication without severe side effects. 

Phase 2 clinical trials determine the effectiveness of a new medication on a disease or condition (like type 2 diabetes) and include 100 to 300 participants. 

Finally, phase 3 trials are conducted at multiple places with several hundred to thousand patients. Phase 3 can last for several years.3 Two phase 3 trials results were released on July 27, 2023.4


What is Mounjaro Used For?


Mounjaro has only been approved by the U.S. Food and Drug Administration (FDA) to help people with type 2 diabetes improve their blood sugar control since May 2022.5 It has not been approved for weight loss at this time. 

Mounjaro (15 mg dose) lowered hemoglobin A1c (HbA1c) by 2.4% compared to a placebo group after 26 weeks in a phase 2 clinical trial including 318 adults with type 2 diabetes. 

HbA1c is the average blood sugar level for the past three months, helping patients and healthcare providers understand the effectiveness of diet, lifestyle, and medications. This level of HbA1c reduction is profound. 

Monitoring the foods you eat and the amount of carbohydrates, reducing added sugar, and pairing fiber, protein, and fat with carbohydrate sources helps maintain healthy blood sugar levels. Tracking blood glucose levels can help you better understand how your body responds to various foods. 

Mounjaro also helped 318 patients with type 2 diabetes achieve superior weight loss in 26 weeks (− 11.3 kg or 25 pounds with a 15 mg dose). This equates to a 21% average weight loss from the start of the trial. 

Obesity is strongly associated with insulin resistance, a precursor in the development of type 2 diabetes. Weight loss helps individuals achieve good blood sugar control.2 

Mounjaro should not be used in patients with type 1 diabetes or people with current or past pancreatitis. It is considered safe and effective for people 18 and older.1,2

How does Mounjaro Work?

Mounjaro works in several ways. After eating foods with carbohydrates, the body responds by releasing insulin from the pancreas. Two main hormones cause the body to release insulin:

  1. Glucagon-like peptide (GLP-1)
  2. Glucose-dependent insulinotropic polypeptide (GIP)

GLP-1 causes insulin to be made and secreted from the pancreas. It also reduces appetite, gastric motility, and stomach emptying. 

GIP also causes insulin to be made and secreted from the pancreas. It can help break down fat storage to be used as energy. 

These are all beneficial things for proper digestion and healthy blood sugar levels

These two hormones, GLP-1 and GIP, do not work properly in patients with type 2 diabetes. This has led to the creation of medications that try to restore the balance of these hormones. 

Mounjaro combines GLP-1 and GIP receptor agonists for a double effect. These receptor agonists contain a chemical that binds and activates receptors on body cells to restore their original function as best as possible. 

The intent is to enhance insulin secretion to return blood sugar levels to a healthy range, lower how much sugar is made in the liver, slow digestion and the rate at which the stomach empties, helping you stay full longer.2

Mounjaro for Weight Loss

As mentioned before, Mounjaro is not approved by the FDA for weight loss treatment alone.5 

Significant weight loss is noted in the clinical trials focusing on people with type 2 diabetes. As hormone levels are restored closer to normal levels in individuals without diabetes, weight loss is a natural side effect. 

Individuals are also advised to eat a balanced diet and increase physical activity, which helps with weight loss.1,2 

Other GLP-RAs, like Wegovy (semuglutide), are approved to aid in weight loss for individuals with a body mass index (BMI) over 30 or those with a BMI of 27 and weight-related medical conditions.6 

The manufacturer of Mounjaro is seeking FDA approval for the medication to be covered for weight management.7 

Of note, almost 5% of the United States adult population has undiagnosed type 2 diabetes.8 Each year, 1.4 million Americans are diagnosed with diabetes.9 

You should seek out medical advice from a health care practitioner if you are concerned you may have type 2 diabetes.

Common warning signs and symptoms of type 2 diabetes include:10

  • Frequent urination
  • Excessive thirst
  • Excessive hunger, even while eating or shortly after eating
  • Extreme fatigue
  • Blurry vision
  • Slow-healing cuts and bruises
  • Tingling, pain, or numbness in hands or feet

What Are the Side Effects of Mounjaro?


While Mounjarp has beneficial effects, all medications can have undesirable side effects. The Mounjaro prescribing information details all side effects (mild and serious) along with contraindications for use.11 

Common Side Effects

The following were the most commonly reported side effects from individuals taking Mounjaro: 

  • Nausea
  • Diarrhea
  • Decreased appetite
  • Vomiting
  • Constipation
  • Heartburn
  • Abdominal pain

Between 5 and 18% of people reported some of these side effects at the 5 mg, 10 mg, and 15 mg doses of Mounjaro. Side effects were more common in the higher dose (15 mg). 

Most gastrointestinal (GI) side effects were reported during dose increases and decreased over time. This is similar to most injectable diabetes medications.

Other Side Effects

Other side effects were reported in less than 5% of the patients. These include:

  • Burping
  • Gas
  • Gastroesophageal reflux disease (GERD)
  • Abdominal distention
  • Mild injection site irritation
  • Mild allergic reactions

Serious Side Effects

Mounjaro has a warning on the manufacturer's website and prescribing information stating severe side effects.1,11 

Serious side effects are not common but should be reviewed with your healthcare provider and your medical history before taking any medication. You should also speak with your doctor is you are pregnant or breastfeeding before taking this medication.
Additionally, birth control pills by mouth may not work as well when taking Mounjaro.

Serious side effects (adverse reactions) include: 

  • Risk of thyroid cancer (C-cell tumors) 
  • If a family history of medullary thyroid carcinoma (MTC) or multiple neoplasia syndrome type 2 (MEN 2) is noted, Mounjora should not be used.
  • Hypoglycemia (low blood sugar levels with insulin, metformin, or sulfonylurea)
  • Acute gallbladder disease (swelling of the gallbladder)
  • Pancreatic hormone increase (amylase and lipase)
  • Acute pancreatitis (swelling of the pancreas)
  • Diabetic retinopathy complications (damage to the blood vessels of the eyes).
  • Kidney problems, such as acute kidney injury or failure
  • Heart rate increase of at least 15 beats per minute
  • Severe allergic reactions
  • Severe gastrointestinal disease

Due to Mounjaro replacing and restoring GLP-1 and GIP hormone levels, when discontinuing or stopping, the beneficial effects stop as well. 

GLP-1 and GIP reduce appetite and hunger, helping you stay full longer and lose weight. These two hormones also lower blood sugar levels.  Long-term or life-long use of Mounjaro is recommended to maintain the effects. 

Weight loss does help your body manage blood sugar levels better, but it does not cure type 2 diabetes. Your hormone levels will likely still be ineffective on their own without the injectable medications.1,2

Learn More About How To Improve Blood Sugar Levels with Signos

Learn more about the importance of managing blood sugar levels on Signos’ blog. Health experts write articles about nutrition and healthy lifestyles

A continuous glucose monitor (CGM) can help you know how your body responds to different foods, beverages, and physical activity. Medications can have undesirable side effects and may affect how you digest food and manage weight after stopping them. 

A Signos’ CGM can help you improve your health without taking medications or help enhance your results when taking diabetes medications. Take a quick quiz to determine if Signos fits your needs.

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Topics discussed in this article:


  1. Mounjaro. (n.d.). Welcome to Mounjaro. https://www.mounjaro.com/
  2. Min, T., & Bain, S. C. (2021). The Role of Tirzepatide, Dual GIP and GLP-1 Receptor Agonist, in the Management of Type 2 Diabetes: The SURPASS Clinical Trials. Diabetes therapy: research, treatment and education of diabetes and related disorders, 12(1), 143–157. https://doi.org/10.1007/s13300-020-00981-0
  3. University of Cincinnati College of Medicine (n.d.). Clinical trials phases defined. https://med.uc.edu/depart/psychiatry/research/clinical-research/crm/trial-phases-1-2-3-defined
  4. Lily Investors. (2023, July 27). Tirzepatide demonstrated significant and superior weight loss compared to placebo in two pivotal studies. https://investor.lilly.com/news-releases/news-release-details/tirzepatide-demonstrated-significant-and-superior-weight-loss
  5. US Food and Drug Administration. (2022, May 13). FDA approves novel, duel-targeted treatment for type 2 diabetes. https://www.fda.gov/news-events/press-announcements/fda-approves-novel-dual-targeted-treatment-type-2-diabetes
  6. Wegovy. (n.d.). Lose weight and keep it off. This is Wegovy. https://www.wegovy.com/
  7. Berthold, J. (2023, September 11). Are the newest weight loss drugs too good to be true? University of California San Fransisco. https://www.ucsf.edu/news/2023/09/426081/are-newest-weight-loss-drugs-too-good-be-true
  8. Centers for Disease Control and Prevention. (2022, September 30). Prevalence of both diagnosed and undiagnosed diabetes. https://www.cdc.gov/diabetes/data/statistics-report/diagnosed-undiagnosed-diabetes.html
  9. American Diabetes Association. (n.d.). Statistics about diabetes. https://diabetes.org/about-diabetes/statistics/about-diabetes
  10. American Diabetes Association. (n.d.). Understanding type 2 diabetes. https://diabetes.org/about-diabetes/type-2
  11. Eli Lilly and Company. (n.d.). Mounjaro-tirzepatitde injection, solution. https://uspl.lilly.com/mounjaro/mounjaro.html#pi

About the author

Sarah Bullard is a registered dietitian and nutrition writer with a master’s degree in nutrition. She has a background in research and clinical nutrition, personalized nutrition counseling, and nutrition education.

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