What is Mounjaro (tirzepatide) & how to get it for weight loss

Losing weight is an enigma to many of us. We try this or that diet, to varying degrees of success, but the battle with the scale continues to slant uphill, as it does for 42% of Americans.

Thankfully, as obesity rates have ballooned in the US, so has the medical community’s understanding of this complex condition. We now know the old standby advice to “eat less and exercise more” just doesn’t cut it for most people. Obesity is a medical condition that often needs medical treatment, which has led to a slew of new weight loss drugs being introduced to the market. 

Tirzepatide, the active ingredient in Mounjaro (approved for type 2 diabetes) and Zepbound (approved for weight loss), is the newest kid on the block when it comes to injectable medications that seem almost like miracle elixirs for weight loss. Tirzepatide has been showing promising effects on weight when combined with lifestyle changes.

Keep reading to learn more about tirzepatide and how it can help with weight loss.

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Mounjaro (tirzepatide) is a once-weekly injectable medication approved by the US Food and Drug Administration (FDA) in May 2022 to help control blood sugar in adults with type 2 diabetes mellitus, and providers have been prescribing this drug for weight loss off-label. 

Most of the injectable weight loss medications on the market are in the same drug class, called GLP-1s (glucagon-like peptide-1 receptor agonists). Mounjaro is a little different. It’s a dual drug that works on both the GLP-1 receptor and another receptor called GIP (glucose-dependent insulinotropic polypeptide). 

It’s this one-two punch that seems to make this diabetes medication work a bit better for weight loss compared to its single-receptor GLP-1 competitors. We’ll get into how this works a bit further down in this article.

While Mounjaro isn’t FDA-approved for weight loss, it’s proving to be one of the most effective drugs we have for helping people with obesity lose weight—and keep it off. That’s why the FDA approved tirzepatide, the active ingredient in Mounjaro, under a different brand name—Zepbound—for weight management. 

Over and over, studies have shown (and continue to show) how effective tirzepatide is at encouraging weight loss in people with obesity—with or without type 2 diabetes. This is significant because people with diabetes generally have a more difficult time losing weight than those without, even using the same interventions. 

Here are some of the studies we have on Mounjaro’s weight loss effects:

• One large study (on over 2,500 people with a BMI of 30 or more, or 27 or more and at least one weight-related complication) showed that over half of the participants taking the highest dose (15mg) of tirzepatide lost 20% or more of their body weight. 

• Another randomized clinical trial compared tirzepatide to semaglutide (brand names Wegovy and Ozempic), the most popular GLP-1 on the market, in people with diabetes. Even at a low dose of tirzepatide (5 mg), study participants lost more weight (8.5% on average) than they did with 1 mg of semaglutide (6.7%). 

So, even when held up against other effective weight loss medications, Mounjaro shines when it comes to weight loss. 

It’s precisely because of its dramatic effects on weight that the FDA agreed to fast-track approval of this diabetes drug to manage weight as well. This is a pretty big deal, considering the FDA only fast-tracked approval for fewer than 300 drugs between January 2012 and December 2022. In other words, this isn’t something they do lightly. 

In early November 2023, the FDA approved Eli Lilly’s new drug Zepbound, which has the same active ingredient as Mounjaro, for chronic weight management. Zepbound is approved for adults with obesity, or those who are overweight and also have weight-related medical problems such as hypertension, and type 2 diabetes mellitus.

Zepbound is the same drug as Mounjaro. Both drugs are injection medications and have the same active ingredient, tirzepatide. They even come with the same strengths (2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg), and are injected weekly, as directed by your healthcare provider. 

The only difference is that Mounjaro is approved for type 2 diabetes, and Zepbound is specifically approved for weight loss. 

So, how does this almost magical-sounding drug work so well at controlling blood sugar and encouraging weight loss? 

As mentioned briefly above, tirzepatide is a dual agonist, meaning it acts on two receptors in the brain and the pancreas—GLP-1 and GIP. These receptors have similar effects in the body, though GIP is far more complex, impacting a wider range of body functions. For the sake of simplicity, we’ll focus on their shared effects. When we eat, the brain naturally kicks the GLP-1 and GIP receptors (also called incretin hormones) into gear, but only for a short time—just a few minutes. This causes a cascade of effects, primarily relating to insulin and appetite. Mounjaro activates these receptors for up to a week. 

Blood sugar control

When it comes to blood sugar control, Mounjaro works by telling the pancreas to make more insulin, which moves sugar from the blood into the cells. It also prevents the liver from releasing more sugar into the blood. This is important in people with diabetes, whose cells don’t absorb sugar easily, and whose livers release excess sugar into the blood. Over time, elevated blood sugar levels can cause damage to the nerves, kidneys, eyes, and heart. 

Weight management

Similar to GLP-1 medications like Wegovy and Ozempic, Mounjaro has an added benefit as a treatment of obesity (defined as having a body mass index, or BMI, of 30 or higher). As we’ve seen, these results can be quite dramatic, with some people without diabetes losing up to 20% of their body weight. 

There are two main ways this works: 

• Mounjaro delays gastric emptying, meaning that when you eat, food stays in your digestive tract for longer, making you feel full for longer and consume fewer calories. 

• It activates receptors in the brain that decrease appetite by making you less interested in food overall, which leads to lower food intake. 

Like any medical intervention, including those for weight loss, Mounjaro keeps working as long as you keep taking it. It stays active in your system for up to a week (that’s why you need to inject it weekly). Once you stop taking it, you can expect any positive (or negative) effects you’ve experienced to reverse. So, if Mounjaro helped you lose weight, you’re likely to see that weight comes back if you stop taking it.

Mounjaro rarely causes dangerous side effects, but it’s not uncommon to experience mild-to-moderate gastrointestinal symptoms, especially when first starting this drug. This is because Mounjaro directly impacts digestion. The most common side effects can include: 

• Nausea

• Diarrhea

• Decreased appetite

• Constipation

• Abdominal pain

• Indigestion

These side effects are dose-dependent, meaning the higher the dose you take, the more likely you are to experience these effects. Still, even at the highest dose of Mounjaro, only about 6.5% of study participants decided to stop taking the medication because they found the side effects affecting their stomach too intolerable. For most people, these side effects may be bothersome, but are generally manageable—and they do tend to get better with time. 

Serious side effects can happen, but are much more common if you have a personal or family history of certain conditions (in which case, your healthcare provider will likely recommend you not take Mounjaro). These include: 

• Medullary thyroid carcinoma (MTC), a specific kind of thyroid cancer for which some studies on rodents have shown an increased risk

• Pancreatitis

• Hypoglycemia

• Allergic reaction

• Acute kidney injury

• Gastroparesis or other severe GI disorders

• Diabetic retinopathy

• Acute gallbladder disease 

If you’re experiencing any uncomfortable side effects while taking Mounjaro, speak with your healthcare provider to get their advice on how to manage your symptoms or make changes to your medication if necessary. 

It’s safe to take Mounjaro with most other medications, but since it affects the digestive system, it can impact how your body responds to oral medications. Your healthcare provider may need to adjust your dosage of other medications if they monitor you and find you need more or less based on how you’re absorbing your medications. 

You’ll also need extra monitoring if you’re taking insulin or any other medications that impact insulin. Low blood sugar is a possible risk with Mounjaro, and this may be exacerbated when taken with other medications that impact blood sugar. 

Mounjaro is a once-weekly injection available in the following dosages: 

• 2.5 mg (for treatment initiation; this dose doesn’t help controlling blood sugar levels) 

• 5 mg

• 7.5 mg

• 10 mg

• 12.5 mg

• 15 mg

Finding your maintenance dose of Mounjaro can take some time, as there’s a relatively slow ramp-up period to make sure you’re tolerating the medication well. You’ll start at 2.5 mg for four weeks, then increase your dose every four weeks in 2.5 mg increments as long as you’re tolerating the lower dose well, up until 15 mg. 

As with most medications, the goal with Mounjaro is to be on the lowest dose possible that gets you the results you want, while tolerating any side effects. For many people, this may mean being on the highest possible dose of 15 mg if that’s what’s necessary to get the desired effects (assuming they’re able to tolerate the side effects at higher doses). For others, this may mean staying at a lower dose of 10 mg, for example. 

If you increase your dose and find the side effects become intolerable, your provider will likely recommend backing off to the previous dose. Once you find the dose that helps you achieve the weight loss you’re looking for (and/or glucose control if you also have diabetes), without intolerable side effects, you’ll stay at that dose long-term. 

Mounjaro comes in a pre-filled, single-dose pen that needs to be injected subcutaneously (meaning, just under the skin of the abdomen, thigh, or upper arm). Subcutaneous injections are relatively painless for most people, as it’s a tiny needle being injected into an area without very sensitive nerve endings. It’s recommended, though, to rotate injection spots so you don’t cause irritation to the area. 

You can inject Mounjaro with or without food, and any time of day is fine, but you should pick a specific day and time to inject each week so you don’t miss a dose (e.g., every Sunday at 6 pm). 

If you do miss a dose, you can inject it as soon as possible within 4 days of your usual injection time, then resume your next weekly dose at the usual time. If more than 4 days have passed, wait until your next scheduled injection and then resume your weekly injections. Store your unopened Mounjaro cartons in the refrigerator (never the freezer). It’s safe to use your Mounjaro pens if they’ve been unrefrigerated for up to 21 days, but if you accidentally freeze a pen, throw it away and do not inject it. 

How to inject Mounjaro

When you’re ready to inject your medication: 

• Wash your hands. 

• Inspect the medication to make sure it’s clear, colorless, and free of any debris. 

• Choose your injection site (in your abdomen, thigh, or upper arm). 

• Pull off the gray needle cap (without touching the needle or unlocking the pen). 

• Press the clear base of the pen against your chosen injection site, then unlock the pen by turning the ring. 

• Press the purple button at the top of the pen and hold it down for up to 10 seconds.

• You should hear two clicks—one when you first press the button, and one that signals the injection is complete. If you don’t hear a second click and 10 seconds have passed, you can check the pen. If you can see the gray plunger, your injection is complete. 

After completing your injection, dispose of your pen in a sharps container or heavy plastic container. Look up your local community guidelines for safely disposing of sharps. 

One of the biggest potential downsides of a drug like Mounjaro is the cost. The cash price (without insurance) is around $1,000–1,200 per month (depending on the pharmacy you use). Some insurers do cover Mounjaro, but since it’s a relatively new drug that hasn’t yet been approved for weight loss, getting coverage can be a challenge. 

Your healthcare provider’s office may be able to help with contacting your insurer to find out about your coverage options. Our Ro Body program offers insurance pre-authorization assistance as well.  

If you don’t have insurance coverage, you may be eligible for a savings card offered through Eli Lilly, the manufacturer of Mounjaro. 

Should cost still be a prohibiting factor, it’s worth checking with your insurance to see if they cover another medication option, such as semaglutide (Wegovy, Ozempic), liraglutide (Saxenda), or dulaglutide (Trulicity). Some of these GLP-1 receptor agonists may be less effective as Mounjaro for weight reduction, but they’re still highly effective when compared to placebo. If you can get another medication covered, you can discuss that option with your healthcare provider.   

By the end of 2023, you won’t have to ask for Mounjaro for weight loss anymore. The reason for that is that the FDA has approved tirzepatide, the active ingredient in Mounjaro, for weight loss under a different brand name. That new drug, which is exactly the same drug as Mounjaro, will is called Zepbound and is meant for people with the following criteria: 

• Either a BMI of 30 or more

• Or a BMI of 27 or higher, along with at least one weight-related condition (such as diabetes, heart disease, or high blood pressure)

In the meantime, you have several options for getting Mounjaro for weight loss. 

You can speak with your primary care provider to see if they’d feel comfortable prescribing it to you off-label. Many do, and it’s becoming increasingly common for patients to get treatment directly through their PCP. 

Another option is to seek out an obesity medicine specialist. Someone who’s done additional training in this field will be very familiar with the ins-and-outs of Mounjaro and other available medicines. 

Finally, you can get your GLP-1 medication shipped right to your door using our Ro Body program, which includes: 

• A prescription for GLP-1 if indicated by your doctor

• Support with navigating insurance coverage

• Personalized health coaching

• Ongoing care from your Ro provider

• An engaging and informative educational program

All of this support translates into our members seeing an average weight loss of 15% of their body weight, when semaglutide is combined with a reduced-calorie diet and increased physical activity.

If you’ve been considering Mounjaro for weight loss, speak with your healthcare provider to see if it, or one of it's alternatives, right for you.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

November 13, 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.