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Tirzepatide Mechanism of Action

Mar 21, 2024
Tirzepatide Mechanism of Action

Tirzepatide is a weight-loss drug that Eli Lilly manufactures under the brand name Mounjaro to treat type 2 diabetes and Zepbound to treat obesity. The tirzepatide mechanism of action (MOA) is similar to that of liraglutide and semaglutide, two other highly successful weight-loss medications. However, tirzepatide is a first-in-class medication because it binds to two receptors instead of one, allowing users to achieve even greater weight loss.

It seems like suddenly, there are a plethora of weight-loss medications available to treat obesity. In 2022, the U.S. Food and Drug Administration approved tirzepatide as an adjunct to diet and exercise to treat type 2 diabetes and, in 2023, to treat obesity. Liraglutide was approved in 2010 to treat diabetes and in 2014 to treat obesity, and semaglutide was approved to treat obesity in 2021.

This sudden increase in available options can make it difficult to understand why one medication may be superior to another. The newness of these medications leads many to wonder how tirzepatide works. How does tirzepatide work for weight loss and as a type 2 diabetes and obesity treatment?

What is tirzepatide?

Tirzepatide is the first weight loss medication that is a dual-acting glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic peptide (GIP) receptor agonist. Semaglutide and liraglutide only target the GLP-1 receptor.

GLP-1 and GIP hormones are secreted from the intestine after you eat. These hormones bind to their receptors in the same way a key fits into a lock. Similar to a lock and key, when a hormone such as GLP-1 or GIP binds to its receptors, it can cause your body’s tissues and organs to produce products such as insulin, change how the brain perceives hunger, or even cause food to move more slowly out of the stomach.

How does tirzepatide work?

GLP-1 and GIP hormones are incretin hormones. Your gut produces these hormones after you consume nutrients high in glucose or fat. These hormones stimulate your pancreas to release insulin. Insulin is a hormone that shuttles glucose from your bloodstream into your liver, muscles, and other body tissues, where it can be stored or used for energy.

Since tirzepatide increases insulin production, it is a very effective treatment for type 2 diabetes, a medical condition in which a person’s pancreas does not produce enough insulin or their body tissues are resistant to insulin’s effect. When insulin levels increase, it suppresses ghrelin release into circulation. This is helpful for weight loss because ghrelin stimulates hunger.1

Besides increasing insulin production, GLP-1 and GIP hormones slow stomach emptying and suppress hunger. By slowing how fast your stomach empties, tirzepatide slows the flow of nutrients from your gut into your bloodstream, which helps stabilize your blood sugar.

GLP-1 receptor agonists also affect appetite regulation in the brain. Many people who take tirzepatide explain that the medication quiets food noise. After taking tirzepatide, they think about food less and feel less hungry. Some even report that they enjoy food less. These effects make it easier to follow a reduced-calorie diet.

What are the potential benefits as a result of tirzepatide’s MOA?

Tirzepatide’s safety and efficacy have been tested in a series of clinical trials. The SURPASS series of clinical trials focused on treating type 2 diabetes, and the SURMOUNT series focused on treating obesity.

In an international 72-week clinical trial, participants without diabetes taking 10 mg of tirzepatide lost an average of 19.5% of their body weight, and those taking 15 mg lost an average of 21% of their body weight. Nine out of every ten participants taking tirzepatide (15 mg) lost at least 5% of their body weight. Participants in the placebo group only showed an average weight loss of 3%. Participants also received lifestyle counseling, consumed a reduced-calorie diet, and participated in an exercise plan.2

Follow-up clinical trials tested tirzepatide’s safety and efficacy in treating participants with diabetes and their ability to continue to lose weight while taking tirzepatide for up to 2 years. These clinical trials showed how well tirzepatide works for weight loss and treating type 2 diabetes.

Tirzepatide MOA has the potential to lead to the following beneficial effects:3,4,5

  • Decreases blood pressure
  • Decreases food cravings
  • Decreases glucagon release from the pancreas
  • Decreases liver fat
  • Increases HDL (good) cholesterol
  • Increases insulin release from the pancreas
  • Increases insulin sensitivity
  • Increases satiety
  • Increases weight loss
  • Lowers blood sugar
  • Protects bone density
  • Protects heart function 
  • Reduces LDL (bad) cholesterol
  • Reduces triglycerides
  • Slows food digestion
  • Suppresses appetite
Tirzepatide Mechanism of Action

What side effects are caused by tirzepatide mechanism of action?

Side effects noted in tirzepatide clinical trials that were reported by at least 5% of people taking tirzepatide include the following:6,7

  • Nausea
  • Diarrhea
  • Decreased appetite
  • Vomiting
  • Constipation
  • Indigestion
  • Abdominal pain
  • Injection site reactions
  • Fatigue
  • Hypersensitivity reactions
  • Increased gas
  • Hair loss

In most cases, the side effects were rated as mild to moderate in intensity. These side effects were more common or worsened when participants first started taking tirzepatide or when their dosage was increased. Tirzepatide is administered at a slowly increasing dose to reduce the potential for side effects.  

Tirzepatide can also cause low blood sugar, especially in people with diabetes. Low blood sugar can present with the following symptoms:

  • Increased sweating
  • Dizziness
  • Blurred vision
  • Anxiety, irritability, or other mood changes
  • Slurred speech
  • Headaches
  • Fast heartbeat

In addition to these more common side effects, tirzepatide can cause some potentially serious adverse effects, such as serious allergic reactions, thyroid cancer, and pancreatitis. If you have a personal or family history of thyroid cancer, let your doctor know before you take tirzepatide. Thyroid cancers and tumors were seen in animal trials and studies, and their relevance to humans is not fully known at this point.

How is tirzepatide administered?

Because of tirzepatide’s MOA and chemical composition, it stays in the body longer than naturally produced GLP-1 and GIP hormones. Tirzepatide is administered once a week as a subcutaneous (just under the skin) injection. The typical tirzepatide dosing schedule starts at 2.5 mg once a week for 4 weeks. The dosage is increased by 2.5 mg every 4 weeks until a maintenance dose is reached.

Tirzepatide is available only by prescription. Compounded tirzepatide is an option when the medication is not available or needs to be customized to meet an individual patient’s needs. The U.S. allows compounding pharmacies to step in and fill the gap between supply and demand if the drug is listed on the drug shortage list. Tirzepatide is currently on this list.

Understanding how tirzepatide works for weight loss is an important step toward determining whether it is an appropriate weight-loss medication option for you. To qualify for tirzepatide, patients must have a body mass index (BMI) of 30 or higher or 27 or higher with a weight-related medical condition. If you meet these criteria and are interested in tirzepatide as a weight loss treatment option, the next step is to talk with a medical provider at Invigor Medical. They will evaluate your medical history and discuss the best weight loss treatment options with you.

How does tirzepatide work to promote weight loss?

Tirzepatide works by mimicking the GLP-1 and GIP hormones naturally secreted by the intestine after a meal. This action prompts insulin secretion, reduces appetite by slowing down stomach emptying, and interacts with the brain to signal fullness, helping individuals eat less and feel satisfied.

What are the benefits of tirzepatide for weight loss compared with other medications?

Tirzepatide works by binding to both GIP and GLP-1 receptors, while other options bind to GIP-1 receptors only. Clinical trials have shown that tirzepatide leads to significant weight loss, with participants losing up to 21% of their body weight, making it an effective option for individuals struggling to shed extra pounds.

Are there any common side effects associated with tirzepatide use for weight loss?

Common side effects of tirzepatide can include nausea, vomiting, diarrhea, or constipation, which tend to resolve over time.

How long do individuals need to take tirzepatide to maintain weight loss results?

Research indicates that individuals may need to remain on tirzepatide long-term to sustain weight loss benefits. Discontinuing the medication can lead to weight regain. This highlights the chronic nature of obesity treatment and the necessity for ongoing therapy for lasting results.

While we strive to always provide accurate, current, and safe advice in all of our articles and guides, it’s important to stress that they are no substitute for medical advice from a doctor or healthcare provider. You should always consult a practicing professional who can diagnose your specific case. The content we’ve included in this guide is merely meant to be informational and does not constitute medical advice.

Tirzepatide Mechanism of Action

Leann Poston, M.D.

Dr. Leann Poston is a licensed physician in the state of Ohio who holds an M.B.A. and an M. Ed. She is a full-time medical communications writer and educator who writes and researches for Invigor Medical. Dr. Poston lives in the Midwest with her family. She enjoys traveling and hiking. She is an avid technology aficionado and loves trying new things.


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