Mounjaro (Injection): Uses, Side Effects, Dosage, and How It Works 

Introduction

Type 2 diabetes mellitus (T2DM) is a chronic condition that can progressively worsen without effective management¹. 

Mounjaro is a recent and advanced management option available for adults with T2DM. It is officially approved as an adjunct to diet and exercise to improve blood sugar control in adults with T2DM^1,2. Besides this, it has also attracted attention due to its effect on weight management in obese individuals³.  

In this article, we will provide a clear and balanced overview of Mounjaro and its role in the evolving landscape of diabetes care. 

What is Mounjaro?

Many people ask, “Is Mounjaro a semaglutide?”  

Well, the answer is “No”. Although Mounjaro is used for a similar purpose, it is not a semaglutide. Mounjaro is actually the brand name for tirzepatide (generic name), which is a drug approved by the U.S. Food and Drug Administration (FDA) in 2022 for managing type 2 diabetes mellitus (T2DM). While both help in lowering blood sugar levels, semaglutide works by activating the glucagon-like peptide-1 (GLP-1) receptor, Mounjaro uniquely stimulates both the GLP-1 receptor and the glucose-dependent insulinotropic polypeptide (GIP) receptor, providing a dual mechanism of action⁴. 

Mounjaro was originally developed to help control the blood sugar levels in adults. However, it has also shown potential in supporting weight management, which has led to its growing use for obesity management as well⁴.

What is Mounjaro Used For?

Mounjaro (tirzepatide) is an FDA-approved medication, currently used as a second-line therapy for management of T2DM along with lifestyle and diet changes⁴. 

In addition to managing blood sugar levels, tirzepatide has shown to be effective in reducing body weight, backing its use for obesity management as well³.  

Clinical trials, such as the SURPASS studies, have demonstrated that tirzepatide leads to greater reductions in glycated haemoglobin (HbA1c) (up to -2.34%) and weight management (up to 11.2 kg) than many existing options, including other GLP-1 receptor agonists like semaglutide^5,6. 

How Does Mounjaro Work?

Mounjaro contains tirzepatide, a synthetic polypeptide and the first dual receptor agonist of its kind, acting on both the⁴: 

• GLP-1 receptor 
• GIP receptor 

While GLP-1 receptor agonists like semaglutide stimulate insulin release and suppress appetite, tirzepatide’s added action on the GIP receptor enhances insulin sensitivity, further improving blood sugar control and supporting weight management⁶. 

Functionally, tirzepatide: 

• Stimulates insulin secretion in response to elevated blood glucose⁶ 
• Decreases the liver’s production and release of glucose⁴ 
• Slows gastric emptying, leading to prolonged satiety (feeling of fullness)⁶ 
• Suppresses appetite by targeting the brain’s hunger centres⁶
• Increases levels of adiponectin, a hormone linked to improved insulin sensitivity⁴

Mounjaro Injection Dosage & How to Use It

Knowing the right Mounjaro dosage and how to use it is key to getting the best results in managing T2DM as well as body weight. A low Mounjaro dose is given as a subcutaneous injection to start with, in order to help your body adjust and is then increased gradually for better blood sugar control and weight management⁴.

Here’s a simple Mounjaro dosage chart^2,4: 

If blood sugar levels need to be controlled further, the dose can be increased by 2.5mg after 4 weeks on the current dose till a maximum dose of 15 mg/ 0.5 mL. However, it requires an expert in the field, like an Endocrinologist, to monitor you regularly while you initiate the treatment and continue the treatment.

If you’re wondering how to use Mounjaro, the injection process is straightforward and can be done in just a few steps. However, it’s important to follow your doctor’s instructions closely and use it only under medical supervision. While there is no specific best time of day to take Mounjaro, it should be administered on the same day each week². 

If you miss a dose of Mounjaro, contact your doctor and take the dose within 4 days (96 hours). If more than 4 days have passed, skip the missed dose and consult your doctor before resuming your next scheduled injection⁴. Avoid taking two doses at once to compensate for a missed dose. If you suspect an overdose or have serious concerns, seek urgent medical help immediately. 

Note: Do not self-medicate; only a doctor can help you determine the best schedule based on your treatment plan.  

How is Mounjaro Injection Supplied and Stored?

Globally, Mounjaro is supplied in various vials and devices. It may be available as a single dose vial, as a single-dose prefilled pen, or a multidose prefilled pen device in various strengths². 

Following the guidelines below on how to store Mounjaro will help maintain its effectiveness and safety. 

Storage Instructions: 

• Keep Mounjaro refrigerated at 2°C to 8°C (36°F to 46°F). 
• It can be stored unrefrigerated up to 30°C (86°F) for 21 days if needed. Remember not to freeze Mounjaro (discard if frozen). 
• Store pens in the original carton to protect them from light².

Expiration & Disposal: 

• Use before the expiration date on the label. 
• Dispose of used pens promptly in an FDA-approved sharps container. Avoid discarding them in regular household trash. 
• If you don’t have an FDA-approved container, use a sturdy, puncture-resistant plastic container with a tight-fitting lid. It must be upright and stable, leak-resistant, and properly labelled for hazardous waste².

Side Effects of Mounjaro

Mounjaro is generally well-tolerated, and most users do not experience severe side effects. However, like all medications, it may cause adverse effects in some individuals, especially during the initial weeks of use. Let us answer some common doubts. 

1. What are some common side effects of Mounjaro?

The most commonly reported side effects of Mounjaro include nausea, vomiting, diarrhoea, constipation, indigestion, decreased appetite, and pain at the injection site^2,4. 

2. What are some rare but potentially serious side effects of Mounjaro? 

Though rare, serious side effects of Mounjaro may include vision changes, inflammation of the pancreas (pancreatitis), severe allergic reactions such as swelling of the face or lips and difficulty breathing, kidney issues, gallbladder problems, gastrointestinal complications, and thyroid tumours (including C-cell tumours)^2,4.

3. How long do Mounjaro’s side effects last?

Most Mounjaro side effects are temporary and last for few days to few weeks after starting treatment, usually until the body adjusts to it. Always speak with your doctor if side effects persist or worsen. 

Note: Mounjaro’s long-term side effects are still being studied, but current data suggest monitoring for potential risks such as thyroid tumours, pancreatitis, and kidney problems.  

4. Does Mounjaro cause constipation?

Yes, constipation is a known side effect of Mounjaro and may occur early in the course of treatment⁴. Consult your doctor if it becomes severe. 

5. Does Mounjaro cause headaches?

Some patients may experience headaches with Mounjaro as a result of low blood sugar². If these are persistent, consult your doctor. 

6. Does Mounjaro cause tiredness?

Fatigue or tiredness is not a widely reported side effect, but dizziness, light-headedness or confusion may occur in some users, especially when experiencing low blood sugar². If fatigue continues, consult your doctor. 

Warnings and Precautions

Before starting, it’s important to review and understand Mounjaro’s precautions. These may include certain groups of people who should not take Mounjaro, such as: 

• Individuals with a personal or family history of medullary thyroid carcinoma (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN-2)⁴. 
• People with a known severe allergy to tirzepatide or other ingredients². 
• Pregnant or breastfeeding individuals (as safety data is lacking)^2,4. 
• People with type 1 diabetes or other forms of non-T2DM². 
• Individuals with a history of severe gastrointestinal disease, gallbladder disease, or diabetic retinopathy need to be cautious². 

What to Tell Your Doctor

Before starting Mounjaro: 

• All existing medical conditions, including pancreas, kidney, eye, or gallbladder issues. 
• Any medications or supplements you’re taking. 
• Any known allergies. 
• If you’re planning a pregnancy or are currently pregnant, or breastfeeding. 

Mounjaro Drug & Food Interactions

While Mounjaro generally has a low risk of food interactions, it’s important to understand how it may interact with certain foods, drinks, and medications. 

Foods and drinks to avoid include: 

• High-sugar and processed foods: While they may not directly counteract Mounjaro’s effects, they may worsen blood sugar control and add on to Mounjaro’s efforts in managing diabetes⁷. 

Medications to use with caution include: 

• Insulin or an insulin secretagogue (such as sulfonylurea): When combined with Mounjaro, these can increase the risk of hypoglycaemia (low blood sugar)². 
• Other GLP-1 receptor agonists (such as semaglutide): Their combined safety and efficacy with Mounjaro have not been established⁴. 
• Oral medications with narrow therapeutic windows (e.g., warfarin) or oral contraceptives: Delayed gastric emptying from Mounjaro may affect absorption and effectiveness². 

Note: Discussing all the medications you take allows your doctor to personalise your treatment and avoid any potential Mounjaro interactions. 

What Happens When You Stop Taking Mounjaro?

When you stop taking Mounjaro, its effects on blood sugar and weight gradually wear off. Blood glucose levels may begin to rise again, and weight that was lost during treatment might return over time (especially if lifestyle habits aren’t maintained)⁸. 

Therefore, always speak with your doctor before stopping Mounjaro so they can adjust your diabetes or weight management plan accordingly and help you transition safely to another therapy if needed. 

Conclusion

Mounjaro is an innovative treatment for T2DM that offers dual action on GLP-1 and GIP receptors, leading to effective blood sugar control and weight management benefits. While generally well tolerated, it may cause side effects like nausea, constipation, or, more rarely, pancreatitis or thyroid-related issues.  

Proper usage, including consistent weekly dosing and safe injection practices, is key to achieving the best outcomes. Also, be sure to consult your doctor before beginning or discontinuing Mounjaro. They will assess your health history, monitor potential interactions, and tailor the treatment to your individual needs to ensure safety and effectiveness. 

Frequently Asked Questions (FAQs)

References

1. Gettman L. New Drug: Tirzepatide (Mounjaro™). Sr Care Pharm. 2023 Feb 1;38(2):50-62. Available from: https://www.ingentaconnect.com/content/ascp/tscp/2023/00000038/00000002/art00004;jsessionid=31pkfi4stv6a8.x-ic-live-01
2. U.S. Food and Drug Administration. Mounjaro (tirzepatide) injection, for subcutaneous use: Highlights of prescribing information. FDA. 2022; [cited 2025 Jun 09]. Available from: https://www.accessdata.fda.gov/drugsatfda_docs/label/2022/215866s000lbl.pdf 
3. Lin F, Yu B, Ling B, Lv G, Shang H, Zhao X, Jie X, Chen J, Li Y. Weight loss efficiency and safety of tirzepatide: A Systematic review. PLoS One. 2023 May 4;18(5):e0285197. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC10159347/ 
4. Farzam K, Patel P. Tirzepatide [Internet]. StatPearls Publishing. 2025; [cited 2025 Jun 09]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK585056/ 
5. Dahl D, Onishi Y, Norwood P, Huh R, Bray R, Patel H, Rodríguez Á. Effect of Subcutaneous Tirzepatide vs Placebo Added to Titrated Insulin Glargine on Glycemic Control in Patients With Type 2 Diabetes: The SURPASS-5 Randomized Clinical Trial. JAMA. 2022 Feb 8;327(6):534-545. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC8826179/ 
6. Nauck MA, D’Alessio DA. Tirzepatide, a dual GIP/GLP-1 receptor co-agonist for the treatment of type 2 diabetes with unmatched effectiveness regrading glycaemic control and body weight reduction. Cardiovasc Diabetol. 2022 Sep 1;21(1):169. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC9438179/ 
7. Reynolds A, Mitri J. Dietary Advice For Individuals with Diabetes [Internet]. South Dartmouth. 2000; [cited 2025 Jun 09]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279012/ 
8. Aronne LJ, Sattar N, Horn DB, Bays HE, Wharton S, Lin WY, Ahmad NN, Zhang S, Liao R, Bunck MC, Jouravskaya I, Murphy MA; SURMOUNT-4 Investigators. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA. 2024 Jan 2;331(1):38-48. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC10714284/ 
9. Organization of Teratology Information Specialists (OTIS). Tirzepatide (Mounjaro®, Zepbound®). MotherToBaby Fact Sheets [Internet]. Brentwood (TN): OTIS. 1994; [cited 2025 Jun 09]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK605070/ 
10. National Institute on Alcohol Abuse and Alcoholism. Harmful Interactions: Mixing Alcohol with Medicines [Internet]. National Institutes of Health; [cited Jun 09]. Available from: https://www.niaaa.nih.gov/publications/brochures-and-fact-sheets/harmful-interactions-mixing-alcohol-with-medicines 

Disclaimer: The information provided here is for educational/awareness purposes only and is not intended to be a substitute for medical treatment by a healthcare professional and should not be relied upon to diagnose or treat any medical condition. The reader should consult a registered medical practitioner to determine the appropriateness of the information and before consuming any medication. PharmEasy does not provide any guarantee or warranty (express or implied) regarding the accuracy, adequacy, completeness, legality, reliability or usefulness of the information; and disclaims any liability arising thereof.