Mounjaro vs. Metformin for Weight Loss

We compare Mounjaro and Metformin for the treatment of obesity to see which may work best for you

Table of Contents
  • Mounjaro
  • Metformin
  • Comparing Mounjaro and Metformin
  • Effectiveness
  • Administration and Dosage
  • Adverse Effects
  • Cost and Coverage
  • Where Can I Find These Medications?

You may have encountered many different medications on your weight loss journey, whether from online sources or personal experience. Of these medications, the GLP-1 medications may have come across your radar. Mounjaro and other GLP-1 agonist medications have been gaining popularity due to their significant weight loss effects for people struggling with obesity. However, some other medications on the market that you may not have known could be used for weight loss. One of these is the popular anti-diabetic medication, Metformin. 

In this blog post, we will compare and contrast these two medications for obesity to better assist you and find the prescription medication that works best for you! 


Mounjaro is a new medication that belongs to the GLP-1 agonist family of anti-diabetic medications. It has been gaining popularity for its off-label use for weight loss and obesity. It is a GLP-1 and GIP dual agonist and works by mimicking these naturally produced gut hormones. By doing this, Mounjaro allows for more insulin secretion from the pancreas, a decrease in the movement of food through the stomach, and regulation of blood sugar levels. This causes a reduction in appetite and food cravings, leading to the weight loss benefits seen when taking Mounjaro.


Metformin is a medication that is most commonly used to treat type 2 diabetes. It is also used for patients with Polycystic Ovarian Syndrome (PCOS) and other diseases involved with insulin resistance. It belongs to a class of drugs known as biguanides. It works by acting on the liver cells to decrease the release of sugar into the blood as well as increasing the body's sensitivity to insulin. It also increases the bread down of fats in the body, which is where the weight loss benefits of this medication are seen. This leads to control of blood sugar levels, increase in insulin sensitivity, and increase of fat metabolism.

Comparing Mounjaro and Metformin

There are a few specific differences between these medications that you should be aware of before starting.


You have probably heard in the news that studies show that Mounjaro is very effective for weight loss. The study these reports refer to is most likely the results from the SURMOUNT-1 trial published in 2022. This study aimed to examine the effects of tirzepatide (Mounjaro) on obesity in non-diabetic patients. The participants taking Mounjaro were followed for a period of 72 weeks. Along with taking Mounjaro, they were also enrolled in a calorie-restricted diet and exercise regiment (~150 minutes/week). 

They found that after 72 weeks, each group taking Mounjaro showed significant weight loss compared to the placebo group. Each treatment group experienced a 15-20% change in weight from the start of the trial, with higher doses showing a more remarkable change (1). It should be noted that the best results were seen in combination with regular exercise and dieting. 

Metformin has been on the market in the US since 1994 for treating diabetes. It was even used by French Physicians for diabetes back in the 1950s! This renowned medication has now been gaining popularity for its use in managing obesity in non-diabetic patients. A study published in 2012 reviewing the long-term safety, tolerability, and weight loss associated with metformin found that participants taking metformin along with diet and exercise noticed a significant reduction in body weight and waist circumference at the end of a 3-year period. Participants taking metformin noticed up to 3.5% reduction in body weight. However, the best results were strongly tied to strict adherence to the medication and the lifestyle changes proposed by the Diabetes Prevention Program. 

When comparing the two studies, Mounjaro has a more significant effect on weight loss, and the results were seen in a shorter period of time. However, the GI side effects seen when taking either of these medications were less common for Metformin compared to Mounjaro (28% vs 85%). It must be noted that the maximum benefit for weight loss for both of these medications was seen when combined with dieting and regular exercise. 

Administration and Dosage

The dosing and administration of Mounjaro is very different from Metformin. Mounjaro is a once-weekly injection that starts at a low dose of 2.5mg and can gradually increase over time.

Metformin is a twice-daily oral tablet that is usually started at around 500mg (1000mg per day) and then is slowly increased to a dose of 2000mg per day divided into a morning dose and an evening dose. The maximum dose for weight loss is 2550 mg per day. It comes in immediate or extended-release formulations. 

Adverse Effects

Gastrointestinal side effects are most common for both of these medications. This includes stomach ache, nausea, vomiting, diarrhea, and decreased appetite. These symptoms are often mild in severity and decrease over time for both medications.

Metformin should be avoided for patients with severe kidney disease, congestive heart failure, acute or chronic metabolic acidosis, and severe liver disease. Though Metformin has been used in pregnant patients with gestational diabetes, there is still no clear answer if it is safe for use in pregnancy. Therefore, you should discuss using Metformin with your provider if you are pregnant or are thinking about becoming pregnant.

Mounjaro should be avoided if you have a history of pancreatitis, gallbladder disease, diabetic retinopathy, history of medullary thyroid cancer or a family history of Multiple Endocrine Neoplasia Cancer Syndrome Type 2 (MEN-2). Mounjaro should also be avoided if you have had low blood sugar (hypoglycemia) episodes or are taking insulin. As of now, Mounjaro should only be used in pregnancy if the benefits of therapy outweigh the risks to the fetus. If you are pregnant or are thinking of becoming pregnant while taking Mounjaro, then you should discuss it with your provider before continuing.

Cost and Coverage

Unfortunately, Mounjaro can be very expensive, depending on your insurance. The average cost for a month's supply of Mounjaro can range from $900-$1000. Depending on your insurance plan, you may also be eligible for the Mounjaro Savings Card, which can allow you to pay as little as $25 per month for Mounjaro. Complete the online savings program enrollment form to see if you can get set up with the savings card and save a lot of money. 

Mounjaro is not currently FDA-approved for the management of obesity, which may make finding coverage by insurance difficult. You may be eligible if you have type 2 diabetes. Ultimately, you should contact your insurance company to see if you are eligible for coverage of Mounjaro and what steps need to be taken to receive coverage. There are also compound forms of Mounjaro that you can get at a lower monthly price. If you would like to know more about compound options for Mounjaro, check out our website at Mochi Health

It should also be noted that some insurance plans require a trial of Metformin therapy for up to 90 days before being approved to transition to Mounjaro or other GLP-1 agonist medications. Therefore, call your insurance plan to discuss what medications are covered and the requirements for coverage. 

Since Metformin has been on the market much longer, it can be a lot less expensive than Mounjaro. Depending on insurance, a monthly supply of Metformin can cost around $7-12. It can even go as low as $0.41 for a month's supply! There are also coupons available through RxSaver that can lower the price to $8-10 if you do not have insurance. 

Where Can I Find These Medications? 

If you would like to learn more about GLP-1 medications or want to see if you might be eligible for medication-assisted weight loss, check out Mochi Health, where board-certified obesity medicine physicians can offer expertise in this realm!


  1. Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, Kiyosue A, Zhang S, Liu B, Bunck MC, Stefanski A; SURMOUNT-1 Investigators. Tirzepatide Once Weekly for the Treatment of Obesity. N Engl J Med. 2022 Jul 21;387(3):205-216. doi: 10.1056/NEJMoa2206038. Epub 2022 Jun 4. PMID: 35658024.
  2. Diabetes Prevention Program Research Group. Long-term safety, tolerability, and weight loss associated with metformin in the Diabetes Prevention Program Outcomes Study. Diabetes Care. 2012 Apr;35(4):731-7. doi: 10.2337/dc11-1299. PMID: 22442396; PMCID: PMC3308305.

Ready to transform your health?

Unlock access to expert guidance and a weight care plan crafted just for you.