What Is Mounjaro Made of? A Guide to Mounjaro’s Ingredients and How It’s Made
Key takeaways:
Mounjaro (tirzepatide) is an injectable medication that’s FDA approved to manage Type 2 diabetes. It contains the active ingredient tirzepatide, along with inactive ingredients that help make the injection more stable and less painful.
Mounjaro doesn’t contain preservatives. This is why the medication comes as single-use pens or vials that should be discarded after use.
Mounjaro is created through a process called solid-/liquid-phase peptide synthesis. This involves attaching protein building blocks together, then filtering and purifying the final product.
Table of contents
Tirzepatide is the main ingredient in Mounjaro, a popular medication for managing Type 2 diabetes. But there are other ingredients needed to make this once-weekly injectable medication. So what are these ingredients? And how is Mounjaro made? Here, you find answers to these questions and more.
What is the active ingredient in Mounjaro?
Tirzepatide is the active ingredient in Mounjaro. It belongs to a medication class with a long name: dual glucose-dependent insulinotropic polypeptide (GIP)/glucagon-like peptide-1 (GLP-1) receptor agonists. It works for diabetes by stimulating your pancreas to release more insulin after eating and lowering how much sugar (glucose) your liver makes.
Tirzepatide is currently one of the largest lab-made peptides. Peptides are a group of two or more amino acids (protein building blocks). Once injected, tirzepatide acts like the natural GIP and GLP-1 hormones found in your body.
Good to know: Tirzepatide is also the active ingredient in Zepbound. But Zepbound is FDA approved for weight loss and obstructive sleep apnea.
What other ingredients make up Mounjaro?
Mounjaro contains several inactive ingredients that help make the injection more stable, less painful, and have a longer shelf life. These other ingredients don’t affect how tirzepatide works to lower your blood sugar.
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In addition to tirzepatide, Mounjaro injections also contain:
Sodium chloride (helps maintain stability, lengthens shelf life, and makes injections less painful)
Sodium phosphate dibasic heptahydrate (buffer to keep Mounjaro stable)
Water for injection (carries tirzepatide into your body)
Hydrochloric acid (adjusts acidity)
Sodium hydroxide (adjusts acidity)
Do Mounjaro vials have different ingredients from Mounjaro pens?
No, Mounjaro vials don’t have different ingredients from Mounjaro pens. In fact, both have the same active and inactive ingredients.
It’s important to note that compounded tirzepatide and Mounjaro are not one and the same. It’s likely that the inactive ingredients in compounded tirzepatide vials are different from FDA-approved Mounjaro vials.
Does Mounjaro contain preservatives?
No, Mounjaro doesn’t contain any preservatives. This is why the pens and vials only contain enough medication for a single dose. You should discard Mounjaro pens or vials immediately after use. Don’t attempt to save them for later, even if there appears to be liquid remaining inside.
Does Mounjaro contain lizard venom?
No, Mounjaro doesn’t contain lizard venom. But exendin-4, a hormone found in the venom of the Gila monster lizard, is similar to your natural GLP-1. Scientists studied it when they were first developing GLP-1 medications.
Exenatide — the active ingredient in Byetta and Bydureon — is a lab-made version of exendin-4. It was the first GLP-1 medication to be FDA approved.
Can any ingredients in Mounjaro cause an allergic reaction?
Yes, it’s possible that any of Mounjaro’s active or inactive ingredients can cause an allergic reaction. And in rare cases, these reactions can be life-threatening and require emergency treatment. If you have any allergies, make sure you and your prescriber review Mounjaro’s ingredients before starting it.
If you experience an allergic reaction, such as a rash or hives, while using Mounjaro, contact your prescriber. But if anything seems severe, such as trouble breathing or swelling of the mouth or throat, call 911 or go to the ER.
How does Mounjaro work? Pharmacists explain the science behind how Mounjaro’s active ingredient, tirzepatide, works.
What it feels like: Three people share their experiences with Mounjaro, which can be beneficial for many people living with Type 2 diabetes.
Possible side effects: Learn about Mounjaro side effects — from diarrhea to hair loss — and how to manage them.
How is Mounjaro made?
Mounjaro is made through a process called hybrid solid-phase peptide synthesis/liquid-phase peptide synthesis (SPPS/LPPS). During this process, amino acids (protein building blocks) are arranged and put together in a certain order to form tirzepatide. Once the tirzepatide is formed, it’s purified and freeze-dried to get the final active ingredient used in Mounjaro pens and vials.
The SPPS/LPPS process helps Mounjaro last longer in the body. Your natural GIP and GLP-1 hormones stay in your body for only a few minutes. On the other hand, Mounjaro’s effects last for about 1 week. This is why you only need to inject doses once a week.
The bottom line
Mounjaro (tirzepatide) is a once-weekly injectable medication that’s FDA approved for Type 2 diabetes. The active ingredient, tirzepatide, is made by attaching certain protein building blocks together. Mounjaro also contains inactive ingredients that help maintain stability, lessen injection pain, and lengthen its shelf life.
Review your medical history with your diabetes care team for any potential allergies. Don’t use Mounjaro if you’re allergic to any of its ingredients.
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References
Chavda, V. P., et al. (2022). Tirzepatide, a new era of dual-targeted treatment for diabetes and obesity: A mini-review. Molecules.
Eli Lilly and Company. (2024). United States Patent: US 11,918,623 B2.
Eli Lilly and Company. (2025). Mounjaro- tirzepatide injection, solution [package insert].
Forbes, J., et al. (2023). Biochemistry, peptide. StatPearls.
Min, T., et al. (2020). The role of tirzepatide, dual GIP and GLP-1 receptor agonist, in the management of Type 2 diabetes: The SURPASS clinical trials. Diabetes Therapy.
National Institute on Aging. (2012). Exendin-4: From lizard to laboratory...and beyond. National Institutes of Health.
Samuelsen, L., et al. (2019). Buffer solutions in drug formulation and processing: How pKa values depend on temperature, pressure and ionic strength. International Journal of Pharmaceutics.
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