What is Mounjaro? - Policy Lab

TL;DR

Mounjaro (tirzepatide) is a once-weekly injectable drug approved for type 2 diabetes.
In the SURPASS clinical trials, tirzepatide lowered A1c levels by around 2 percentage points over about 40 weeks, with many patients reaching an A1c below 7%.
Mounjaro has a boxed warning for thyroid tumors, based on animal studies, and is typically avoided in people with a personal or family history of thyroid cancer.
Because Mounjaro slows the emptying of the stomach, it may decrease the absorption of oral drugs. It may also increase the risk of low blood sugar when taken with insulin or sulfonylurea drugs.

Treatment options have expanded over the years when it comes to type 2 diabetes. GLP-1 medications are some of the newest drugs, approved for managing blood sugar levels and weight loss.

Medications like Monunjaro go one step further in targeting both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1), two key hormones involved in regulating blood sugar. Despite the potential costs of the drug, its health benefits as a once-weekly injection can’t be ignored.

How Mounjaro Works

The active ingredient in Mounjaro, tirzepatide, works as a dual GIP and GLP-1 receptor agonist. At a molecular level, it mimics two natural hormones that are involved in regulating blood sugar levels and appetite. The GIP and GLP-1 hormones are typically released after eating a meal, but their levels may be lower in someone with type 2 diabetes.

GIP and GLP-1 help stimulate the pancreas to release insulin, another hormone that helps the body transport blood sugar or glucose into the body’s cells for energy. Tirzepatide also suppresses the release of glucagon, decreasing the amount of glucose secreted from the liver.

In addition to its direct effects on blood sugar, tirzepatide helps slow the emptying of the stomach. As a result, it can help increase feelings of fullness after eating, decreasing a person’s caloric intake and promoting weight loss. GLP-1 agonists may also help regulate brain regions involved in appetite to help manage weight.

FDA-Approved Uses & Who’s a Candidate

Mounjaro is a brand-name drug that was first approved by the U.S. Food and Drug Administration (FDA) in 2022. It’s currently only approved to help control blood sugar in adults with type 2 diabetes, and it’s prescribed for use alongside a diet and exercise plan.

The active ingredient is approved under the brand name Zepbound for weight loss in people who are obese with a body mass index (BMI) of 30 or over. It’s also approved for people who are overweight with a BMI of 27 to under 30 with a weight-related condition like high blood pressure or high cholesterol. More recently, Zepbound was approved to help manage obstructive sleep apnea (OSA) in adults with obesity.

In some cases, brand-name Mounjaro may be prescribed off-label for weight loss, especially in people with type 2 diabetes who are overweight or obese. That said, Mounjaro is typically taken at lower doses for diabetes than the higher doses used with Zepbound for weight loss.

Mounjaro is not approved for type 1 diabetes or diabetic ketoacidosis (DKA).

Dosing & Titration (Weekly Injection)

Mounjaro is given as a subcutaneous injection (under the skin), usually in the stomach area, thigh, or upper arm. It’s a once-weekly injection that can be taken with or without food. However, it should be injected on the same day each week for steady drug levels.

Treatment with Mounjaro is started at a low dose to help reduce the risk and severity of side effects like nausea and constipation. The dose can then be increased slowly over time through a process called titration to help the body adjust.

The usual dosage schedule of Mounjaro is as follows:

2.5 mg once weekly for 4 weeks (starting dose).
5 mg once weekly after at least 4 weeks on the 2.5 mg dose.
If blood sugar goals aren’t reached on the 5 mg dose, the dosage may be increased by 2.5 mg after at least 4 weeks on the 5 mg dose.
The dosage can be increased in 2.5 mg intervals every 4 weeks up to a maximum of 15 mg once weekly.

Not everyone needs to take the maximum dose. Most people reach their blood sugar goals on 5 mg or 10 mg, depending on how they respond to the drug and whether they experience side effects at higher doses.

For those who miss a dose, the dose can be taken within 4 days (96 hours) of the missed injection. If more than 4 days have passed, it’s best to skip the missed dose and take the next one as scheduled. The chosen day for the weekly injection can be changed as long as doses are at least 3 days apart.

Mounjaro pens are prefilled and single-use, which means no dose measuring is required.

How Well Does Mounjaro Work?

Mounjaro has been shown to have strong effects on reducing A1c, a blood test that shows a person’s average blood sugar levels over the previous two to three months. It’s one of the standard ways to analyze how well diabetes medications work.

Large clinical trials have found that Mounjaro is effective, even in people who are already on diabetes medications like metformin. In many cases, people with type 2 diabetes have been able to lower their A1c levels to their recommended targets (below 7%).

Mounjaro Efficacy At A Glance

Trial Name	Patient Population	Study Duration	Average A1c Reduction (Estimated)
SURPASS-1	Type 2 diabetes, not on injectable treatment	40 weeks	1.9% to 2.1%
SURPASS-2	Type 2 diabetes on metformin (vs semaglutide)	40 weeks	2.0% to 2.3%
SURPASS-3	Type 2 diabetes on oral medication (vs insulin degludec)	52 weeks	1.9% to 2.4%
SURPASS-4	Type 2 diabetes with high cardiovascular risk	52 weeks	2.4% to 2.6%

A large percentage of patients in the SURPASS trials were able to reach an A1c of below 7%, with some even achieving below 6.5%. Higher doses typically led to greater improvement in A1c, although improvements were still seen at the standard doses. In addition to reducing A1c, these studies also found significant weight-loss effects.

Still, Mounjaro may not work the same for everyone. Different factors like baseline A1c, other medications being taken, and how a person reacts to the medication can affect how well it works.

Safety, Side Effects & Warnings of Mounjaro

As with other prescription drugs, Mounjaro may come with side effects. Most side effects are related to the digestive tract, like nausea and an upset stomach, and often depend on the dose. Side effects usually occur during the first weeks of treatment or after increasing the dose.

Mounjaro Boxed Warning

Mounjaro has a boxed warning for thyroid tumors, which is based on studies in animals. There may be an increased risk of thyroid tumors in humans based on data from the FDA Adverse Event Reporting System (FAERS).

Because of the boxed warning, Mounjaro is not recommended for people who:

Have a personal or family history of medullary thyroid carcinoma (MTC)
Have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)

Common Side Effects of Mounjaro

The most common side effects include the following:

Nausea
Diarrhea
Vomiting
Constipation
Decreased appetite
Stomach or abdominal discomfort

These side effects are normal and often improve as the body gets used to the medication. That’s also why the dosage is started low and gradually increased.

It’s important to consult a healthcare provider and stop Mounjaro if any of the following occur:

Signs of pancreatitis, such as severe abdominal pain that spreads to the back
Signs or symptoms of an allergic reaction, such as a rash, trouble breathing, or swelling of the face or throat
Severe vomiting or dehydration
Severe or worsening stomach pain
Worsened vision problems caused by diabetes (diabetic retinopathy)

Although rare, gallbladder problems have also been reported in some people taking Mounjaro.

Pregnancy and Breastfeeding While on Mounjaro

Mounjaro is generally avoided while pregnant. When it comes to breastfeeding, there’s not enough research to suggest whether it’s safe for the mother or the nursing child. Those who are planning to get pregnant or breastfeed should consult a healthcare provider for the best option.

Drug Interactions of Mounjaro

Mounjaro can interact with other medications, so it’s important to tell a healthcare provider about all medications being taken before starting treatment. That includes prescription drugs, over-the-counter medicines, and herbal or dietary supplements.

Oral drugs: Since Mounjaro can slow the emptying of the stomach, it could decrease the absorption of drugs that are taken by mouth. Drugs that depend on absorption, such as warfarin and hormonal birth control pills, could be seriously affected. A non-oral birth control method is recommended during the first 4 weeks after starting Mounjaro and after each increase in dose.
Insulin and sulfonylureas: Medications like insulin and sulfonylureas, such as glimepiride and glyburide, may need to be adjusted while taking Mounjaro. Taking Mounjaro with these drugs could increase the risk of low blood sugar (hypoglycemia), which could cause symptoms like confusion, sweating, rapid heartbeat, dizziness, and fatigue.

Special Populations

Some people may need to use extra caution before taking Mounjaro. These include:

Older individuals who may be more prone to digestive side effects and serious problems from dehydration
People with pancreatitis, since GLP-1 medications have been associated with pancreatitis in rare cases
Severe gastrointestinal diseases or blockages, as Mounjaro can slow gastric emptying and worsen these conditions
Children or adolescents under 18, since Mounjaro isn’t approved for these individuals

Discussing medical conditions with a healthcare provider is key before starting Mounjaro.

Mounjaro vs. Ozempic: What’s the Difference?

Mounjaro and Ozempic are both weekly injections used for type 2 diabetes. However, Mounjaro contains the dual GIP/GLP-1 agonist tirzepatide, while Ozempic contains the GLP-1 agonist semaglutide. In other words, Mounjaro targets two hormones, while Ozempic only targets one.

Approved Uses

Mounjaro is currently approved for type 2 diabetes only. Ozempic has more FDA-approved uses apart from type 2 diabetes, including reducing the risk of heart attacks and strokes in people with heart disease and type 2 diabetes. Ozempic is also approved to help prevent severe kidney problems like kidney failure in people with chronic kidney disease and type 2 diabetes.

Efficacy for A1c and Weight Loss

The SURMOUNT-5 and SURPASS-2 trials show that tirzepatide is generally more effective than semaglutide. Those taking tirzepatide for type 2 diabetes or weight loss experienced greater reductions in A1c and body weight than those taking semaglutide. These results are most likely due to tirzepatide’s dual action versus the single action of semaglutide.

Side Effects

Mounjaro and Ozempic can cause similar side effects, such as nausea, diarrhea, constipation, and lower appetite. At higher doses, Mounjaro may cause more side effects than Ozempic. Side effects are usually more common at the start of treatment or after dose increases. Everyone reacts differently, with some people experiencing mild side effects or none at all from either medication.

Access, Cost, and Coverage of Mounjaro

Mounjaro is relatively new and is only available as a brand-name medication. It usually has a higher cost than other diabetes medications, especially those with generic versions.

Without insurance, the retail price of a 28-day supply of Mounjaro could be up to $1,000 or more, depending on the pharmacy. Insurance coverage, including commercial and Medicare or Medicaid coverage, can depend on the plan or state.

Some private insurance plans cover Mounjaro for type 2 diabetes, although insurance companies usually require prior authorization. That means a healthcare provider will have to provide documentation of medical necessity or recommend other medications first (step therapy) before Mounjaro can be covered.

Savings options are available for people with or without insurance. For example, the manufacturer offers a savings card for eligible patients with commercial insurance, potentially reducing the costs to $25 for up to 3 months.

Prescription discount cards could help reduce the cash pay for those without insurance. In addition, some reputable telehealth platforms offer compounded versions of tirzepatide that are just as effective but at a reduced cost.

Practical Use: Lifestyle and Adherence Tips

Mounjaro works best when it’s taken consistently with balanced lifestyle changes, such as a nutritious diet and regular exercise. A regular schedule for weekly injections and small changes in habits can also help make Mounjaro more effective and easier to tolerate.

Choose one day each week to make the injection and take note of the day, or set reminders to avoid missed doses.
Rotate the injection sites between areas on the stomach, thigh, or upper arm.
Eat smaller meals throughout the day to help manage nausea or indigestion.
Focus on protein and fiber to help keep muscle mass and manage blood sugar while on Mounjaro.
Avoid large meals with high-fat, greasy foods, which could worsen digestive side effects.
Drink plenty of fluids throughout the day, even while experiencing side effects like nausea or constipation.
Try to get at least 150 minutes of moderate-intensity aerobic exercise per week.
Take note of side effects and blood sugar trends as recommended by a healthcare provider.

Having the right lifestyle habits can make a difference in improving blood sugar levels more than taking tirzepatide alone.

FAQs

How long does it take for Mounjaro to start working?

Mounjaro starts working after the first dose, but it may take several weeks before blood sugar levels improve. It could take 2 to 3 months to see an improvement in A1c levels since A1c levels show blood sugar trends over time.

Can you lose weight on Mounjaro if you have diabetes?

Yes, many people who take Mounjaro for type 2 diabetes also notice weight loss since it can decrease appetite. Weight loss may be seen at higher doses, which is why the active ingredient is approved under the brand name Zepbound for this purpose.

Is Mounjaro better than Ozempic for A1c reduction?

Mounjaro has been shown to reduce A1c more than Ozempic at standard doses. However, both medications are effective for managing type 2 diabetes.

What happens if you stop taking Mounjaro?

Blood sugar levels could increase after stopping Mounjaro, especially if lifestyle habits like diet and exercise haven’t been maintained. Studies also suggest that people regain weight after stopping Mounjaro, which is why it’s important to have a plan before stopping it, such as adhering to lifestyle changes or staying on a lower maintenance dose.

Does Mounjaro cause hair loss?

Hair loss is not a listed side effect of Mounjaro. However, some people may experience nutritional deficiencies due to dietary changes while on the medication. Deficiencies in B vitamins, for example, could cause hair loss.

Can Mounjaro be taken long-term?

Mounjaro is generally taken as a long-term medication for type 2 diabetes. A healthcare provider will recommend regular follow-up visits to make sure it’s working safely and effectively.