Description
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.
- Weight loss: 20.2% with tirzepatide vs.13.7% with semaglutide
- Average weight loss: 50.3 lbs with tirzepatide vs. 33.1 lbs with semaglutide
- Waist circumference reduction: 7.2 inches with tirzepatide vs. 5.1 inches with semaglutide.
Mounjaro (tirzepatide) received FDA approval on May 13, 2022. There is no Mounjaro generic. The 2 different brands of tirzepatide (Mounjaro and Zepbound) are made by Eli Lilly and Company but are FDA-approved for different conditions.
- Mounjaro: Specifically approved for type 2 diabetes management in adults.
- Zepbound: Designated for weight loss treatment in adults.
- See Zepbound vs Mounjaro: Comparison Guide for Weight Loss and Diabetes Treatment.
Mounjaro Side Effects
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.
The side effect of hypoglycemia was generally low in Mounjaro monotherapy trials but increased when used with insulin or sulfonylureas. Injection site reactions, including pain, redness, and swelling, were commonly reported but typically mild in severity.
Approximately 5-10% of patients discontinued Mounjaro due to side effects in clinical trials, with higher discontinuation rates (up to 25% in some studies) at the highest doses (15 mg), and lower rates (around 5%) at lower doses (5 mg). The discontinuation rate is dose-dependent, with gastrointestinal side effects being the primary reason for stopping the medication.
Timeline for Common Side Effects
- Week 1-2: Peak intensity of gastrointestinal symptoms
- Week 3-4: Gradual improvement begins
- Week 4-8: Most patients experience a significant reduction in side effects
- After 8 weeks: Side effects are typically minimal or resolved.
Tips for Managing Stomach Side Effects
Following these tips may help you manage stomach side effects:
- Eat more slowly
- Consume smaller meals
- Select more bland, low-fat foods (like crackers, toast, and rice)
- Avoid greasy, fried foods or sugar treats
- Eat foods that contain water (like soup or gelatin)
- Don’t lie down right after eating
- Drink clear or ice-cold liquids
- If possible, go outside for fresh air if you feel sick to your stomach.
FDA Boxed Warning and Serious Side Effects
Mounjaro may cause serious side effects, such as thyroid tumors (Boxed Warning), inflammation of the pancreas, low blood sugar levels, gallbladder problems, kidney problems, serious gastrointestinal side effects, and serious eye problems or allergic reactions. It can also increase the risk of food or liquid getting into your lungs during surgery or a medical procedure.
Thyroid Cancer Risk (Boxed Warning):
Animal studies report that Mounjaro has caused cancerous and non-cancerous thyroid tumors in rats. While the human risk remains unknown, you should tell your healthcare provider if you develop any of the following symptoms:
- A lump or a swelling in your neck
- A hoarse voice that doesn’t improve or a persistent cough
- Difficulty swallowing or breathing.
Do NOT use Mounjaro if you have:
- A personal or family history of medullary thyroid carcinoma (MTC)
- Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
Pancreatitis (Severe Pancreas Inflammation):
Mounjaro may increase the risk of acute pancreatitis, which is a potentially life-threatening condition requiring immediate emergency care. Symptoms of pancreatitis include:
- Severe abdominal pain that won’t subside
- Pain radiating from your abdomen to your back
- Nausea and vomiting with severe pain
- Fever and rapid pulse
- Abdominal tenderness.
Action required: Stop Mounjaro immediately and seek emergency medical care.
Hypoglycemia (Dangerously Low Blood Sugar levels):
Mounjaro may cause low blood sugar (hypoglycemia), particularly when combined with other diabetes medications such as insulin, sulfonylureas (glipizide, glyburide, glimepiride), or other glucose-lowering drugs. Warning signs of low blood sugar levels include:
- Dizziness, lightheadedness, confusion
- Sweating, shakiness, tremors
- Blurred vision, slurred speech
- Fast heartbeat, palpitations
- Anxiety, irritability, mood changes
- Hunger, weakness, fatigue
- Drowsiness, feeling jittery.
