Tirzepatide is the first medication in a new drug class sometimes known as a twincretin, because it targets two hormone receptors that regulate insulin and metabolism. Although tirzepatide was initially developed to treat type 2 diabetes, it has demonstrated significant effects on weight loss and has been rapidly adopted under the brand names Mounjaro (for diabetes) and Zepbound (for obesity).
The high demand for these drugs has resulted in shortages, so many patients and providers have turned to compounded tirzepatide, created at specialty pharmacies. If you are considering your options, it is essential to understand how tirzepatide works and the differences between the FDA-approved and compounded versions of this medication.
What Is Tirzepatide Peptide?
Tirzepatide is a synthetic peptide that consists of 39 amino acids. Amino acids are the building blocks of proteins. Peptides are short amino acid chains. They serve many important bodily functions. In addition to being the foundation of all proteins, they are involved in the immune system, tissue repair, signal transmission between cells, and the regulation of cellular function.
Tirzepatide mimics the action of two natural hormones released by intestinal cells: glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). These hormones, known as incretins, are secreted after eating and play critical roles in regulating appetite, stimulating the release of insulin, and processing carbohydrates and fats.
Tirzepatide acts on both GLP-1 and GIP receptors, which increase insulin secretion, slow stomach emptying, decrease appetite, and improve glucose control.
Insulin, Glucagon, and Blood Sugar Control
Maintaining a healthy blood sugar balance depends on the coordination of insulin and glucagon. These two peptide hormones, secreted by the pancreas, regulate blood sugar by acting on various cells and tissues throughout the body.
Insulin
- Insulin signals cells to take up glucose from the blood and convert it to glycogen, a form of carbohydrate storage in the liver and skeletal muscle.
- Glycogen is composed of chains of glucose molecules that can be rapidly broken down into glucose when the body requires energy.
- Insulin also stimulates the uptake of glucose by fat cells, which then synthesize fat from glucose for longer-term storage.
- Insulin lowers blood sugar.
Glucagon
- Glucagon, by contrast, is released when blood sugar is low. I
- Glucagon signals the liver to break down glycogen into glucose for energy.
- Glucagon also stimulates glucose production from non-carbohydrate sources such as amino acids, a process known as gluconeogenesis.
- Glucagon typically increases blood sugar.
How Does Tirzepatide Peptide Work?
Tirzepatide shifts the balance of insulin and glucagon toward greater insulin action and reduced glucagon release, leading to improved glucose control and decreased hunger.
Tirzepatide’s dual action sets it apart from medications like semaglutide (Wegovy or Ozempic):
GLP-1 activity
- Increases the number of pancreatic betal cells
- Stimulates insulin secretion by beta cells
- Increases insulin sensitivity
- Increases clearance of triglycerides (a type of cholesterol)
- Breaks up fats
- Delays stomach emptying
- Acts on the brain’s appetite centers to promote fullness
GIP activity
- Mainly acts on pancreas
- Decreases glucagon release by the pancreas
- Increases insulin release
- Promotes fat storage
- Supports the synthesis of glycogen
People with type 2 diabetes often have abnormally low levels of GIP, or their pancreatic cells do not respond normally to GIP to release an adequate amount of insulin with food intake. People with obesity often have elevated GIP levels, since dietary fat stimulates GIP secretion.
The combined action of tirzepatide makes it highly effective in lowering hemoglobin A1C in individuals with diabetes and supporting sustained weight loss in those with obesity.
Manufacturing Shortages Led to Compounded Tirzepatide
Although Mounjaro is FDA-approved for the management of type 2 diabetes, doctors also prescribe it “off-label” for weight loss. Off-label prescribing refers to the use of a medication for a purpose other than its original FDA-approved indication. Zepbound is the same drug, but it is FDA-approved for weight loss in people with obesity. Neither drug currently has a generic version.
Due to the high demand for the drugs, a shortage of tirzepatide began in 2022 and lasted until December 2024. During this period, the FDA added tirzepatide to its drug shortage list and worked with the manufacturer to increase production. Although the shortage has largely been resolved, occasional supply issues persist at some pharmacies.
When a drug is on the shortage list, state-licensed compounding pharmacies are permitted to prepare compounded drugs that closely match the FDA-approved product. The active ingredient remains the same, although a compounding pharmacy may add or remove non-essential ingredients.
Compounded medications may also be prepared to remove allergens, create a liquid form for patients who cannot swallow pills, or adjust the dose strength to meet a specific patient’s needs.
What Is Compounded Tirzepatide?
Compounded tirzepatide has the same active ingredient as the FDA-approved brands. In some cases, an additional ingredient, such as vitamin B12, may be added. Compounded tirzepatide is legal, widely available through state-licensed compounding pharmacies, and often less expensive than brand-name versions.
Is Compounded Tirzepatide the Same as the Brand?
While compounded tirzepatide contains the same active ingredient as Mounjaro and Zepbound, there are some important differences:
• FDA-approved tirzepatide undergoes rigorous clinical testing and quality control. Compounded tirzepatide is not FDA-approved because it has not undergone the same review process, despite containing the same active peptide.
• Compounding pharmacies may prepare tirzepatide in different concentrations or delivery forms (such as multi-dose vials instead of prefilled pens).
• Quality may vary depending on the pharmacy. Patients should always obtain compounded tirzepatide from reputable, state-licensed pharmacies.
• In October 2024, the tirzepatide shortage was resolved, which limited compounding to patient-specific needs.
Why Many Patients Choose Compounded Tirzepatide
Compounded tirzepatide remains an attractive option for many patients. Cost is a major driver, since Mounjaro and Zepbound can cost more than $1,000 per month without insurance coverage. For uninsured patients or those denied coverage, compounded tirzepatide may be significantly more affordable.
Others prefer compounded tirzepatide because compounding pharmacies may offer dosing flexibility or added ingredients such as vitamin B12. For these reasons, patients should consult with their providers and always choose a reputable, state-licensed compounding pharmacy.
Key Takeaways
• Tirzepatide is a novel twincretin therapy that improves glucose control and promotes weight loss.
• Compounded versions of tirzepatide were created to provide an option for patients during drug shortages. It contains the same active peptide as the brand versions.
• FDA-approved products (Mounjaro, Zepbound) are still considered the gold standard for safety and consistency.
• Patients considering compounded tirzepatide should only obtain it from licensed pharmacies and under close medical supervision.
Concluding Thoughts
Tirzepatide is the first medication in a new class of drugs that target both the GLP-1 and GIP pathways. It has dramatically improved the management of type 2 diabetes and obesity.
Compounded tirzepatide provides an effective alternative for some patients, especially during shortages or when cost is a concern.
Providers should guide patients through their options — whether FDA-approved brands, insurance assistance programs, or compounded formulations — to ensure that the benefits of tirzepatide are realized safely and effectively.
References
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Frias JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus placebo or active comparators in patients with type 2 diabetes: a systematic review and meta-analysis. *Lancet Diabetes Endocrinol.* 2021;9(12):776-785. doi:10.1016/S2213-8587(21)00274-7. PMID: 34656237. Hamza M, Papamargaritis D, Davies MJ. Tirzepatide for overweight and obesity management. Expert Opin Pharmacother. 2025;26(1):31-49. doi:10.1080/14656566.2024.2436595
Gudeman J, Jozwiakowski M, Chollet J, Randell M. Potential risks of pharmacy compounding. Drugs R D. 2013;13(1):1-8. doi:10.1007/s40268-013-0005-9
Liu L, Shi H, Xie M, Sun Y, Nahata MC. Efficacy and safety of tirzepatide versus placebo in overweight or obese adults without diabetes: a systematic review and meta-analysis of randomized controlled trials. Int J Clin Pharm. 2024;46(6):1268-1280. doi:10.1007/s11096-024-01779-x
Nauck MA, Müller TD. Incretin hormones and type 2 diabetes. Diabetologia. 2023;66(10):1780-1795. doi:10.1007/s00125-023-05956-x
Qureshi N, Wesolowicz L, Stievater T, Lin AT. Sterile compounding: clinical, legal, and regulatory implications for patient safety. J Manag Care Spec Pharm. 2014;20(12):1183-1191. doi:10.18553/jmcp.2014.20.12.1183
Rosenstock J, Wysham C, Frías JP, et al. Efficacy and safety of a novel dual GIP and GLP-1 receptor agonist tirzepatide in patients with type 2 diabetes (SURPASS-1): a double-blind, randomised, phase 3 trial. Lancet. 2021;398(10295):143-155. doi:10.1016/S0140-6736(21)01324-6Improves Beta-cell Function and Insulin Sensitivity in Type 2 Diabetes. J Clin Endocrinol Metab. 2021;106(2):388-396. doi:10.1210/clinem/dgaa863
Timko RJ. Applying Quality by Design Concepts to Pharmacy Compounding. Int J Pharm Compd. 2015;19(6):453-463.
U.S. Food and Drug Administration. FDA clarifies policies for compounders as the national GLP-1 supply begins to stabilize. Published 2024. Available at: https://www.fda.gov/drugs/drug-safety-and-availability/fda-clarifies-policies-compounders-national-glp-1-supply-begins-stabilize. Accessed September 24, 2025.
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