What is Mounjaro?
Mounjaro is used for type 2 diabetes to help lower blood sugar levels. Mounjaro has also been shown to help with weight loss and maintain the lost weight in clinical trials when combined with diet and exercise. It is a once-weekly injection that can be self-administered and should be used alongside dietary changes and exercise.

Mounjaro works by activating two gut hormone receptors, GIP and GLP-1, to manage blood sugar. This stimulates insulin release when glucose is high, reduces liver glucagon production, slows stomach emptying to control post-meal sugar spikes, and increases fullness to reduce appetite and food intake. 
Mounjaro's dual mechanism of action makes it significantly more effective than semaglutide for weight loss, which only activates GLP-1 receptors, as demonstrated in the head-to-head Surmount-5 clinical trial (NCT05822830), which reported an overall 47% greater weight loss with tirzepatide (Mounjaro, Zepbound) compared to semaglutide.
 
Common Side Effects
Common Mounjaro side effects include nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion, abdominal pain, heartburn, fatigue, injection site reactions, headache, and low blood sugar (in people with type 2 diabetes).
Stomach or gastrointestinal side effects are common but tend to be mild and clear up in a few weeks in most people and will not interfere with long-term treatment. Stomach side effects can be more common with higher doses.
The most common gastrointestinal side effect is nausea, which occurs in 12% to 22% of people taking Mounjaro at therapeutic doses, according to clinical trials.
Others include diarrhea (12% to 16%), vomiting (6% to 9%), decreased appetite (5% to 11%), constipation (6% to 7%), indigestion (4% to 7%), abdominal pain (4% to 6%), and injection site reactions (3.2%).
These side effects occurred at rates higher than in placebo-treated groups (receiving an inactive treatment).
These Mounjaro side effects occurred in 4% or more of type 2 diabetes patients taking tirzepatide in pooled placebo-controlled clinical trials.