Medication Comparison

Mounjaro vs. Zepbound: What You Need to Know

Zepbound and Mounjaro, variations of tirzepatide, show significant potential for weight management by mimicking natural hormones in the body. Consulting healthcare providers like MD Exam is essential for personalized guidance on these medications.


  • Thursday, April 11, 2024

What is Zepbound?

Zepbound (tirzepatide) is a medication developed by Eli Lilly and initially approved for medical use in the United States in November of 2023. It was approved by the U.S. Food and Drug Administration (FDA) as an adjunct to diet and exercise for chronic weight management in adults with obesity. Zepbound contains the same active ingredient as Mounjaro, but is approved for treatment of obesity rather than diabetes. It is administered once weekly via a pen self-injected under the skin.

What is Mounjaro?

Surprise! Mounjaro is nearly the exact same medication as Zepbound. Mounjaro (also tirzepatide) is a medication developed by Eli Lilly and initially approved for medical use in the United States in May of 2022, roughly a year earlier than Zepbound. It was also approved by the FDA as an adjunct to diet and exercise to improve blood sugar in adults with type 2 diabetes, not for weight management. However, so many participants in the clinical trials for diabetes lost weight on tirzepatide that they got it approved separately for diabetes and obesity as two distinct brands. Mounjaro rose so quickly in popularity that Eli Lilly sold $1 billion of Mounjaro in just 3 months of 2023!

How Do They Work?

Like other popular medications Ozempic, Wegovy, and Rybelsus, Zepbound and Mounjaro work by mimicking GLP-1 (glucagon-like peptide-1) hormone receptors, receptors in the gut responsible for feelings of fullness. Unlike these other medications, however, Zepbound is a dual-acting medication, so it also activates GIP (glucose-dependent insulinotropic polypeptide) receptors.

By mimicking naturally occurring hormones in the body, the following effects occur:

  • Increased insulin secretion, resulting in lower blood sugar
  • Decreased glucagon production, a hormone the pancreas uses to regulate blood sugar and believed to play a part in signalling feelings of fullness
  • Slowed gastric emptying, which can make individuals feel fuller, longer

Most of these effects are also seen by medication like Ozempic and Wegovy, which also mimic the GLP-1 hormone and activate receptors. Mounjaro and Zepbound, however, also activate GIP receptors. This dual action, though still not entirely and completely understood, is part of the reason tirzepatide has shown evidence of increased weight loss over other medications.

How Much Weight Can You Lose?

There have been a number of studies exploring the effectiveness and safety of tirzepatide, chiefly the SURMOUNT trials, a series of clinical trials funded by Eli Lilly and used in the approval process of Zepbound by the FDA. Most of the information on the Zepbound label came from data collected during these trials. For simplicity we will only be including the trials focused on weight loss for tirzepatide, rather than the diabetes focused trials used for Mounjaro. Mounjaro and Zepbound taken at the same doses would have the same effects.

The SURMOUNT 1 trial consisted of 2539 adults with a BMI of 30+ or 27+ with another weight related complication. Individuals with diabetes were excluded and participants were treated for 72 weeks at 4 different doses, including placebo. The SURMOUNT 1 trial found the average person lost 20.9% of their bodyweight on the highest dose over 72 weeks of treatment. The SURMOUNT 2 trial, which only included diabetic individuals, found the average person lost 14.7% of their body weight at the highest dose over 72 weeks of treatment.

The most frequently reported side effects were related to the gastrointestinal system, which is in line with other medications that target the GLP receptor, such as Ozempic and Wegovy. These side effects were mostly mild to moderate in intensity and occurred mainly when the dose was increased. Treatment discontinuation due to adverse events was observed in 4.3%, 7.1%, 6.2%, and 2.6% of participants receiving tirzepatide doses of 5 mg, 10 mg, 15 mg, and placebo, respectively. Overall, between 78.9% and 81.8% of participants treated with tirzepatide reported experiencing at least one adverse event during the treatment period, compared to 72.0% of participants in the placebo group.

What Are The Most Common Side Effects?

The most common observed side effects at the medium dose (10mg) are listed below. Note this is not a complete list of all side effects.

  • Nausea - 33.3%
  • Diarrhea - 21.2%
  • Constipation - 11.7%
  • Dyspepsia (indigestion) - 9.7%
  • Vomiting - 10.7%
  • Headache - 6.8%
  • Abdominal pain - 5.3%

It is worth noting that 15.4% of participants also contracted COVID during the course of the study, which could have had an affect on other side effect reports. Most of the side effects were mild in nature and subsided over time. 6% of participants reported serious side effects, but there were similar percentages of serious events in the tirzepatide and placebo groups.

How Do You Get Started?

Before jumping into using tirzepatide for weight loss, it's crucial to talk to your healthcare provider – maybe even at a place like MD Exam! We have a simple questionnaire where you share your medical history and we set you up with a personalized weight loss plan. We believe deeply in accessibility, which is why we offer medications at . Semaglutide and tirzepatide have seen the most success with the fewest side effects, so the medical team at MD Exam prefers these treatments over less effective options, but we are dedicated to finding the right option for every individual. Most patients of MD Exam start with semaglutide, only switching to tirzepatide if they want more weight loss and afford a more expensive treatment. Healthcare professionals, like the MD Exam team, play a big role in understanding overall health, creating personalized treatment plans, and explaining the possible risks and benefits. Feel free to check us out here

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