Mounjaro (tirzepatide) vs Ozempic (semaglutide): what is the difference?

Injectable weight loss drugs have become all the rage in the news and across social media—but, unlike most popular weight loss trends, this one has legs.

There are many drugs on the market now with strong evidence for helping people lose weight and keep it off, especially when combined with lifestyle changes like diet and exercise. Two such drugs—Mounjaro and Ozempic (see Important Safety Information)—don’t yet have FDA approval as weight loss medications, but they’re often prescribed off-label for this purpose.

How do Mounjaro and Ozempic compare? What can you expect from these drugs? Keep reading to find out more. 

Mounjaro (tirzepatide) and Ozempic (semaglutide) are both injectable medications approved by the US Food and Drug Administration (FDA) along with diet and exercise for controlling blood sugar levels in people with type 2 diabetes. Ozempic is also approved for preventing cardiovascular events (like heart attack or stroke) in people who have both type 2 diabetes and heart disease. It’s important to mention that both drugs are not a type of insulin, and they don’t help treat type 1 diabetes. Instead, they help regulate blood sugar in other ways (more on that below).

While neither of these type 2 diabetes medications is approved (as of this writing) for weight loss, they’ve both proven effective at helping people with obesity or excess body weight lose weight. Because of this, many providers prescribe these drugs off-label to help with weight loss if they decide this is the best option for their patient.

These drugs have a lot in common, but how do they differ? The main distinction is they’re slightly different types of drugs:

• Ozempic is a type of drug called a glucagon-like peptide-1 receptor agonist (often called GLP-1s for short).

• Mounjaro is a combination drug that acts on the GLP-1 receptor along with another receptor in the brain called glucose-dependent insulinotropic polypeptide (GIP).

GLP-1 and GIP are two hormones called incretins, involved in many functions, including controlling how much insulin the pancreas releases into the blood when blood sugar levels spike (the reason these drugs treat type 2 diabetes), how quickly food moves through the digestive system, and the brain’s appetite signals. The body naturally activates these receptors when we eat, but only for a short burst.

Drugs like Mounjaro and Ozempic keep these receptors activated for much longer (up to a week), which prevents too much sugar from circulating in the blood (leading to lower blood sugar), slows down digestion, and tells the brain you’re satiated (keeping you fuller for longer). 

Is Mounjaro a GLP-1?

Mounjaro is the first drug of its kind to get FDA approval. It’s a “dual agonist,” meaning it’s both a GLP-1 receptor agonist and a GIP receptor agonist. GLP-1 and GIP have similar functions in the body (though GIP is involved in many more processes). Mounjaro activates both of these receptors, controlling blood glucose, sending satiety signals to the brain, and slowing down the process of food moving through the gut.

Studies show that both Ozempic and Mounjaro work well at helping people with obesity lose weight and sustain that weight loss for as long as they stay on the drug.

You’re probably wondering which of these weekly injections works better for weight reduction, though.

While both Ozempic and Mounjaro have led to significant weight loss in study overweight and obese participants (when combined with lifestyle changes), Mounjaro seems to offer more impressive weight loss results when taken at the highest available dose.

• Studies on semaglutide (the active ingredient in Ozempic and Wegovy; see Important Safety Information) show participants lost an average of up to 7% of their body weight in one year when they combined the weekly injection of 1mg with diet and exercise, outshining the placebo group by several percentage points.  A weekly dose of 2.4 mg of semaglutide has been shown to lead help people lose an average of 15% of body weight

• With Mounjaro, more than half of the participants in one study lost over 20% of their body weight (on the highest dose — 15mg per week — of tirzepatide). This amount of weight loss is unparalleled by any weight loss intervention other than bariatric surgery. 

Of course, every person is going to respond differently, and the dose has a big impact. Just because Mounjaro shows better weight loss results in clinical trials doesn’t mean it’s the better drug for you. There are many factors in figuring out which one is best for you.  Your tolerance of one drug’s side effects might not be the same as the other’s, and cost can be a factor, too. Your healthcare provider will help you decide which is right for you.

As of now, these drugs are not yet FDA-approved for weight loss. They’re both approved as diabetes drugs, to control blood sugar in adults with type 2 diabetes.

It’s unlikely that Ozempic will get approval as a weight loss drug, since its active ingredient, semaglutide, is already available at a dose of 2.4mg as a weight loss drug under another brand name, Wegovy.

Mounjaro is likely to get FDA-approval as a weight loss drug sometime in 2023. In October 2022, Eli Lilly, the manufacturer of Mounjaro, announced the FDA’s decision to fast-track approval of the drug for weight management in people with a body mass index (BMI) over a certain threshold. 

The active ingredients in these two drugs cause very similar side effects, which mostly affect your stomach to your intestines. These symptoms can include:

• Nausea

• Diarrhea

• Vomiting

• Constipation

• Abdominal pain

One of the primary ways Ozempic and Mounjaro work to encourage weight loss is by slowing down how quickly food moves through the digestive system—hence, all these digestive symptoms. Many people experience decreased appetite with Ozempic and Mounjaro. This comes from a combination of food moving more slowly through the gut and the brain telling the body that it’s full. And, of course,  the stomach upset would make anyone feel less hungry, as well

Nausea is the most common side effect with both drugs, affecting up to 20% of trial participants at higher doses of Mounjaro and Ozempic. Still, the vast majority of people are able to tolerate the side effects, and they do get better over time. 

Another area where Mounjaro and Ozempic stack up pretty evenly is cost. 

The average out-of-pocket cost for Mounjaro is about $1,100 per month, while the average out-of-pocket cost for Ozempic is around $1,000 per month. 

Your insurance may cover one or either of these drugs, in which case you’ll just need to pay your copay or up to your deductible, depending on your plan. You may want to call your insurance provider to find out which of these drugs they’re more likely to cover (if any) before making your decision. You can also get help with insurance authorization through your provider’s office or through our Ro Body Program. 

If your insurance doesn’t cover either drug, you may be eligible for the drug manufacturer’s savings program. Eli Lilly offers a savings program for Mounjaro, and Novo Nordisk offers a savings program for Ozempic. 

Cost certainly isn’t the only factor in determining which drug is right for you, but these are expensive drugs, so every bit helps and may play an important role in your decision. 

You might think that one drug is good, so maybe two is better, but it’s true what they say: Too much of a good thing isn’t really good. You shouldn’t take more than one GLP-1 (or combination drug) at a time. These drugs are safe and meant to be used long-term, but should not be taken together.

If you’re not getting the results you want from one drug, speak with your prescribing provider about your options. 

The contraindications are the same for both of these drugs. You shouldn’t take these medications if you develop or have a history of:

• Medullary thyroid carcinoma (a certain type of thyroid tumor)

• Pancreatitis

• Acute kidney injury

• Acute gallbladder disease

If you’re taking any medications for high blood pressure, you may need extra monitoring to make sure your blood pressure doesn’t drop too low. And since these medications lower blood sugar, your provider will monitor you for hypoglycemia, especially if you’re on insulin or taking other drugs that affect blood sugar.

You should not take these medications if you’re pregnant or planning to get pregnant.

There are several reasons you might consider switching from Ozempic to Mounjaro (or vice versa): 

• Side effects—Even though both drugs cause similar side effects, you may tolerate one more than the other. If you’re taking one drug and find the side effects too disruptive, your provider might suggest trying another drug. 

• Cost—If your insurance coverage changes, and your plan no longer covers one drug, you might need to switch to another drug that is covered. 

• Effectiveness—If you’re not seeing strong enough effects on your weight with one drug, you may get better effects from another drug. 

If you’re on one of these medications currently and decide you want to stop and try something else, make sure you speak with your healthcare provider first. They can help you figure out which drug will be most appropriate for you to try next, and can help you make a plan for adjusting your medication schedule.

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Current version

March 29, 2023

Written by

Rachel Honeyman

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.