Mounjaro (tirzepatide) is a once-weekly injectable medication that the U.S. Food and Drug Administration (FDA) has approved to help manage blood sugar levels in adults with type 2 diabetes. It is typically taken along with dietary and lifestyle changes.
However, many people are interested in Mounjaro for weight loss. Although the FDA has not officially approved it for this purpose, it can be prescribed off-label—meaning it is taken in a way the FDA has not specifically approved.
Mounjaro's active ingredient is also available under the brand Zepbound, which the FDA has approved for weight management. Therefore, you may be prescribed Zepbound over Mounjaro if you are seeking obesity treatment and qualify.
This article will discuss Mounjaro and its potential for weight loss, whether it's effective, how to get a prescription, safety information, and more.
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Is Mounjaro a Weight Loss Medication?
Currently, the FDA has not approved Mounjaro for weight loss specifically. It has only approved it for controlling blood sugar in adults with type 2 diabetes.
However, healthcare providers may prescribe Mounjaro off-label (for a non-FDA-approved use) for weight loss because clinical trials have shown that this medicine can significantly help.
Mounjaro was FDA-approved in 2022 and is classified as a glucose-dependent insulinotropic polypeptide (GIP) receptor and glucagon-like peptide-1 (GLP-1) receptor agonist. In November 2023, the FDA approved a new drug called Zepbound specifically for weight loss in people who are obese or overweight with at least one weight-related condition, such as sleep apnea or high blood pressure.
Zepbound contains the same active ingredient as Mounjaro (tirzepatide), but the FDA has only approved it for weight loss.
The FDA granted Eli Lilly and Company, the manufacturer of Mounjaro and Zepbound, a Fast Track designation to develop Zepbound. A Fast Track designation is a process that speeds up the development and review of medicines for serious conditions with unmet medical needs, helping to get essential treatments to the public more quickly.
Are Mounjaro and Zepbound the Same?
Mounjaro and Zepbound both contain the same active ingredient, tirzepatide. However, this does not necessarily mean they are interchangeable.
Mounjaro is specifically FDA-approved for people with type 2 diabetes. Zepbound, on the other hand, is FDA-approved for weight loss. Because they are approved for different uses, insurance coverage for each may differ.
Does It Work?
During clinical trials for type 2 diabetes, researchers discovered that tirzepatide was not only effective in controlling blood sugar and lowering hemoglobin A1C (a measure of average blood sugar levels over three months) but also helped participants lose weight.
In a 40-week study (called the SURPASS-1 study) with participants from India, Japan, Mexico, and the United States, tirzepatide significantly improved blood sugar levels and resulted in weight loss ranging from about 15.4 to 21 pounds. Compared to a placebo (inactive medicine), tirzepatide was more effective in lowering blood sugar and helping with weight management.
In the 72-week SURMOUNT-1 trial, tirzepatide was tested for weight loss in people with obesity, with the following results.
- Depending on the dose, participants using tirzepatide lost between 15% and 20% of their body weight.
- In comparison, those receiving a placebo lost only 3% of their body weight.
- The trial found that 85% to 91% of those on tirzepatide lost at least 5% of their body weight, while only 35% of those on a placebo did.
- Additionally, 50% to 57% of people taking the higher doses of tirzepatide lost 20% or more of their body weight, compared to 3% in the placebo group.
This study helped to show tirzepatide’s effectiveness in providing significant and sustained weight loss in people with obesity.
How Does Mounjaro Work for Weight Loss?
Mounjaro works in several ways to control blood sugar and also help with weight loss:
- It increases insulin production, which helps lower blood sugar levels.
- It decreases glucagon levels, which also helps to lower blood sugar.
- It slows stomach emptying, which decreases appetite and contributes to weight loss.
To maintain the effects of Mounjaro, you need to keep taking the medicine. In a study to see if tirzepatide helps maintain weight loss, people who took the drug for 36 weeks initially lost about 21% of their body weight.
When they were randomly assigned to either keep using tirzepatide or switch to a placebo for another year, the people who stayed on tirzepatide kept off a significant amount of their weight.
In contrast, those who switched to the placebo regained most of the lost weight. This shows that continuing tirzepatide is effective in not only maintaining but also enhancing weight loss compared to discontinuing the treatment.
How Does Mounjaro Compare to Ozempic?
Ozempic (semaglutide) is a once-weekly injectable medicine that can help control blood sugar in people with type 2 diabetes. Similar to Mounjaro, Ozempic is also prescribed off-label for weight management.
The manufacturer of Ozempic, Novo Nordisk, also developed a drug specifically for weight loss, called Wegovy. Wegovy also contains semaglutide, the same ingredient in Ozempic.
In a 40-week study comparing tirzepatide to semaglutide for type 2 diabetes, tirzepatide was more effective at lowering blood sugar levels. People using tirzepatide had a more significant reduction in hemoglobin A1C than those on semaglutide.
Tirzepatide at all doses (5 milligrams (mg), 10 mg, and 15 mg) was more effective than Ozempic, with the greatest improvement seen in the higher-dose groups. Additionally, Mounjaro led to more significant weight loss compared to Ozempic.
Overall, Mounjaro was more effective, leading to better weight loss benefits than Ozempic did.
Another study showed that more adults receiving tirzepatide had a 5% or greater weight loss compared with semaglutide, although both were beneficial.
How to Get Mounjaro for Weight Loss
To get a prescription for Mounjaro, follow these steps:
- Schedule an appointment with a licensed healthcare provider, such as a primary care doctor, nurse practitioner, physician assistant, or endocrinologist. You may also set up a telehealth appointment to discuss your eligibility for Mounjaro.
- Your healthcare provider may order blood tests to check your blood glucose levels and hemoglobin A1C.
- During your visit, your provider will review vital statistics, including your weight and blood pressure. They may also inquire about your medical and family histories.
- If you meet the criteria, your healthcare provider can send your Mounjaro prescription to your preferred pharmacy.
- Note that insurance coverage varies, so you may want to check with your insurance plan before you visit with your healthcare provider to see if it covers Mounjaro or any similar alternatives and find out what your out-of-pocket costs would be. You can also check the Mounjaro manufacturer's website for other savings options.
Dosage
Because Mounjaro is not FDA-approved for weight loss, there are no specific dosing guidelines for this use. The general dosing instructions are as follows:
- Mounjaro is administered via a subcutaneous injection under the skin of the stomach, thigh, or upper arm. You should use a different injection site each time and avoid injecting where you administer other medicines or where the skin is tender, hard, lumpy, thick, scarred, or damaged.
- You should inject Mounjaro once per week on the same day. You can choose any time of the day for the injection, which you can take without regard to food. Stick to the same day each week, and if you need to change your injection day, follow the manufacturer's instructions.
- The typical starting injection dose is 2.5 mg once a week.
- After four week weeks, you can increase the dose to 5 mg once a week.
- Your healthcare provider may gradually increase the dose after at least four weeks on a dose, up to a maximum of 15 mg injected once a week.
Your healthcare provider will provide a detailed schedule for taking Mounjaro, and you should follow their instructions carefully.
Side Effects
The most common side effects of Mounjaro are stomach-related and include:
- Nausea
- Vomiting
- Diarrhea or constipation
- Upset stomach
- Feeling less hungry
In rare cases, serious side effects may occur. If you have symptoms of an allergic reaction, you should get emergency medical help. These symptoms may include:
- Hives or itching
- Shortness of breath
- Swelling of the face, lips, tongue, or throat
Other rare but possible side effects that require immediate medical attention may include:
- Inflammation of the pancreas: Stop using Mounjaro and call your healthcare provider right away if you have severe stomach pain (which may spread to the back), with or without vomiting.
- Hypoglycemia (low blood sugar): Ask your healthcare provider if and when you should check your blood sugar and what to do if you have low blood sugar. Some of the symptoms of hypoglycemia include dizziness, weakness, confusion, and hunger.
- Kidney problems or kidney failure: Kidney damage can occur as a result of dehydration due to other side effects, such as vomiting or diarrhea.
- Severe stomach problems: Contact your provider if you experience severe nausea, vomiting, or diarrhea.
- Vision changes: Call your healthcare provider if you notice any vision changes while using Mounjaro.
- Gallbladder problems: Call your healthcare provider immediately if you have upper stomach pain, fever, clay-colored stools, or yellowing of the skin and whites of the eyes.
Precautions
Mounjaro has a boxed warning, the most serious warning required by the FDA. The warning states that Mounjaro has caused thyroid tumors in animal studies. Whether this risk applies to humans is unknown. If you take Mounjaro, be alert to symptoms of thyroid cancer and call your healthcare provider right away if you experience any of the following:
- A lump in the neck
- Hoarse voice
- Trouble breathing
- Trouble swallowing
Because of this risk, the following people should not take Mounjaro:
- People with a personal history or family history of medullary thyroid carcinoma (MTC)
- People with multiple endocrine neoplasia syndrome type 2 (MEN2)
People allergic to tirzepatide or any ingredient in Mounjaro also should not use this medicine.
Summary
Mounjaro is an injectable medication approved for managing blood sugar in people with type 2 diabetes. Though it's not officially approved for weight loss, it can sometimes be prescribed off-label for this purpose and has shown potential in helping with weight reduction.
Zepbound, on the other hand, contains the same active ingredient and has been approved by the FDA specifically for chronic weight management.
Some of the most common side effects of tirzepatide include nausea, vomiting, and diarrhea. If you're interested in taking it for weight loss, make an appointment with your healthcare provider to discuss your options.
