Wegovy / Ozempic and Mounjaro for Weight Loss…Facts and Fiction

What are Wegovy / Ozempic and Mounjaro?  How do they work?

Wegovy and Ozempic are the same medication, semaglutide, a glucagon-like peptide-1 (GLP-1) agonist.  Mounjaro (a generic name is “tirzepatide”) is a GLP-1 receptor agonist and a glucose-dependent insulinotropic polypeptide (GIP) receptor agonist.  The GLP-1 and GIP receptors lead to increased insulin secretion by your pancreas and increased sensitivity to insulin. They also block your liver from producing sugar. This combined effect helps to reduce blood sugar levels.  GIP slows down the emptying of the stomach and lowers stomach acid. There are also GLP-1 receptors in the brain, and it’s thought these drugs work in the brain to suppress appetite. These drugs stimulate receptors throughout the body to suppress appetite, lower blood sugar, and ultimately, assist with weight loss. 

Wegovy and Ozempic are longer-acting versions of older GLP-1 medications such as Victoza, Saxenda, and Trulicity, which you may have previously heard of.

Are Wegovy/Ozempic and Mounjaro approved for weight loss?

In June 2021, the Food and Drug Association (FDA) approved Wegovy (2.4 mg once weekly) for chronic weight management in patients with a body mass index (BMI) of 27 kg/m2 or greater who have at least one weight-related medical problem or in patients with a BMI of 30 kg/m2 or greater. Weight-related medical issues include type 2 diabetes, high cholesterol, and high blood pressure.  Multiple other medical problems are aggravated by obesity…these include sleep apnea, arthritis/joint problems, back pain, and even urinary incontinence. 

Mounjaro is currently not FDA-approved for weight loss but is being studied for that purpose and is commonly prescribed “off-label” for weight loss in the US. Ozempic is only FDA-approved for treating type 2 diabetes but is also often prescribed off-label for weight loss.

How much weight will I lose with Wegovy and Mounjaro?

In a 5 ½ year study, Wegovy patients starting at 232 lbs lost an average of 35 lbs. This equates to about 15% weight loss over the five years. One-third of these patients lost 46 lbs or more.  Roughly 14% of Wegovy patients fail to lose more than 5% of their weight.  Some patients are considered “non-responders” to Wegovy and don’t lose much weight.  

Mounjaro participants taking 15 mg of the medication achieved average weight reductions of 15.7%, losing up to roughly 34 pounds. Those taking 10 mg lost up to 13.4% or almost 30 pounds over a 6-year study.

Other benefits to Wegovy, Ozempic, and Mounjaro. 

Mayo Clinic researchers found that one year of Wegovy lowered the risk of heart attack and stroke by 1.3% over ten years.  Although this doesn’t sound like much, stroke and heart attack can be devastating and lethal, and cardiovascular disease is prevalent in the US population.  Since Wegovy and Ozempic are the same medication, they will lower your blood sugar and hemoglobin A1C, and most patients will also experience blood pressure and cholesterol improvements.

With Mounjaro:

  • Nearly half of the participants (46-49%) could lower their hemoglobin A1C to normal.
  • Fasting blood sugars decreased by an average of 50 mg/dL.
  • Triglyceride levels decreased by more than 27%.
  • Fasting insulin also decreased.

What are the side effects?

Of course, as with every medication, there are also risks. More common side effects associated with Wegovy (and their percentages in clinical trials) include:

  • Nausea (44%)
  • Diarrhea (30%)
  • Vomiting (24%)
  • Constipation (24%)
  • Stomach pain (20%)
  • Headache (14%)
  • Fatigue (11%)
  • Heartburn (9%)
  • Dizziness (8%)
  • Stomach bloating (7%)
  • Burping/flatulence (7%)
  • Low blood sugar in people with type 2 diabetes (6%)
  • Gas (6%)
  • Gastroenteritis (6%)
  • Acid reflux (5%)
  • Stomach irritation (4%)
  • Viral gastroenteritis (4%)
  • Hair loss (3%)

Wegovy may cause inflammation of the pancreas (pancreatitis), gallbladder problems (including gallstones), low blood sugar, kidney damage, diabetic retinopathy (damage to the eye’s retina), increased heart rate, and suicidal behavior or thinking.

Wegovy and Mounjaro have not been studied in clinical trials with patients with a history of pancreatitis.  Patients who develop pancreatitis with either drug should stop taking it immediately. Both drugs may increase the risk of thyroid cancer. Patients with Multiple Endocrine Neoplasia syndrome type 2 should not take these medications.

The side effects are generally the same with Mounjaro and Wegovy, but many experts think the side effects tend to be more severe overall with Mounjaro since its hormonal effects are greater.

Why do some patients not lose weight with Wegovy/Ozempic and Mounjaro?  

According to endocrine surgeon Dr. Jim Norman, the top four reasons patients fail to lose weight are…

  1. snacking between meals
  2. eating desserts and sweets
  3. continuing to eat unhealthy food
  4. not putting forth some effort

In years past, there have been dozens of diet pills and drugs.  We used to have Phen-Fen, phentermine, Meridia, Dexadrine, Orlistat, over-the-counter “fat burners,” Alli, HCG, and the list goes on. Many have been removed from the market based on serious side effects.  Hundreds of unapproved herbal weight-loss supplements are sold to unwary customers. Many have marketing showing dramatic pictures/testimonials where patients have lost extreme weight, but these results have not been scientifically studied. The FDA advised consumers not to purchase herbal weight loss products as recently as June 2023 and they specifically called HCG a “fraud.”

Let’s face it, it’s hard to lose weight, and you must eat a healthier diet and put forth some effort.  Otherwise, you will pay for Mounjaro for six years and regain all your weight…just like with phentermine.

How much do these drugs cost?

Novo Nordisk (the drug maker for Wegovy) advertises that a patient may pay as little as $0 for the first 12 prescriptions. Otherwise, Wegovy may cost $500 per month, but weight loss medications are in high demand, and the supply is sometimes limited.  Eli Lilly, the maker of Mounjaro, offers a $25 savings card to get a 1-month or 3-month prescription of Mounjaro.  After that, you will pay the market price.  If you have health insurance, some plans may not cover these medications; others may charge your copay.  Medicare and Medicaid plans may vary based on location as to whether these medications are covered.

Wegovy/Mounjaro vs. bariatric surgery (gastric sleeve and gastric bypass)

According to the American Society for Metabolic and Bariatric Surgery (ASMBS),

  • Patients may lose as much as 60% of excess weight six months after bariatric surgery and 77% as early as 12 months after surgery.
  • On average, patients maintain 50% of their excess weight loss five years after surgery.5

This equates to about 50 lbs of weight loss at five years.  Although this sounds about the same as Wegovy and Mounjaro, there are fundamental differences.  Bariatric surgery…

  1. reduces your calorie intake by reducing the size of your stomach
  2. makes it harder to regain weight when your stomach is smaller
  3. reduces how many calories you absorb (with some operations)
  4. can help the patient with behavior modification…if you overeat, you get sick.
  5. reduces hunger hormones
  6. has been scientifically studied for 40 years
  7. long-term complications are understood
  8. has been shown in multiple studies to save healthcare dollars. No medication has done that.
  9. when compared to weight loss medications (optimal medical management), bariatric surgery resulted in significantly more weight loss and fewer medications.

Related Bariatric Surgery Information


  1. Jens Juul Holst. The physiology of glucagon-like peptide 1.  Physiol Rev. 2007 Oct;87(4):1409-39. 
  2. Wegovy website. https://www.wegovy.com/about-wegovy/how-does-wegovy-work.html
  3. Agency for Healthcare Research and Quality website.
  4. FDA website…Tainted Weight loss Products…https://www.fda.gov/drugs/medication-health-fraud/tainted-weight-loss-products
  5. ASMBS website on Effectiveness of Metabolic and Bariatric Surgery. https://asmbs.org/resources/metabolic-and-bariatric-surgery#:~:text=Patients%20may%20lose%20as%20much,of%20their%20excess%20weight%20loss.