How Long Does It Take for Mounjaro to Work? Plus 5 More Mounjaro FAQs

Mounjaro (tirzepatide) is a once-weekly injection that can help lower blood glucose (sugar) in adults with Type 2 diabetes. It works best when combined with a diabetes-friendly diet and regular exercise. The active ingredient in Mounjaro — tirzepatide — is also approved for weight loss under a different brand name: Zepbound.

Mounjaro is the only diabetes medication in its class. And it may work better than similar Type 2 diabetes medications.

But how long does it take for Mounjaro to work? And is it safe to use? Here are answers to these and other common questions about Mounjaro.

1. How long does it take for Mounjaro to work?

Mounjaro starts to work in your body within hours of the first injection. Some people have reported noticing its initial effects, such as feeling fuller after eating, within as little as 12 hours.

This timeframe can vary, though. Clinical trials show that people typically start experiencing Mounjaro’s glucose-lowering effects about 4 weeks after starting treatment. And it’s possible that you’ll notice some weight loss during this same period.

These benefits should continue as your body adjusts to the medication. Mounjaro’s full glucose-lowering effects peak around 4 to 6 months after starting it.

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Weight loss typically continues longer than this. Studies that looked at tirzepatide’s weight loss effects ran for over 1 year. People lost the greatest amount of weight during the first 8 months after starting tirzepatide. And those that continued using it were able to maintain this weight loss long term.

2. How does Mounjaro work?

Mounjaro is a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. It acts like GIP and GLP-1, two gut hormones in the body. These hormones help balance glucose levels and regulate appetite.

Mounjaro lowers your blood glucose by:

• Encouraging your pancreas to release more insulin after you eat

• Decreasing the amount of new glucose your liver makes

• Moving glucose from your blood into your cells more efficiently

• Making your body more sensitive to its natural insulin

Mounjaro also has effects that help promote weight loss. These include:

• Slowing the passage of food from the stomach to the intestines

• Targeting areas of the brain that regulate appetite and food cravings

• Balancing levels of hunger hormones in the body

These actions are why Mounjaro is sometimes prescribed off-label for weight loss.

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• Can a nutritious diet boost Mounjaro’s effects? One woman discusses how her diet has changed and become more health-focused since she started Mounjaro.

How much does Mounjaro lower A1C?

Clinical trials show that Mounjaro can lower your A1C by as much as 2% at the highest dosage (15 mg per week). Your hemoglobin A1C (HbA1c or A1C) represents your average blood glucose over the past 3 months.

About 90% of people using Mounjaro were able to get their A1C lower than 7% (a common goal for people with diabetes). What’s more, about half of Mounjaro users lowered their A1C to less than 5.7%. People without diabetes typically have A1C levels of 5.7% or less.

3. How much body weight may you lose with Mounjaro?

In clinical trials, people lost as much as 28 lbs after using the highest dose of Mounjaro (15 mg) for about 10 to 12 months. In these same trials, close to 90% of participants using this dose lost at least 5% of their starting body weight. And 45% of people lost at least 15%.

Everyone’s experience with Mounjaro and weight loss is unique. In general, higher doses typically lead to greater weight loss. But these doses are also more likely to cause digestive side effects, such as nausea and diarrhea.

4. How long does Mounjaro stay in your system?

Mounjaro is a long-acting medication. Small amounts of the medication may be in your system for up to 25 days. But its effects start to wear off after about a week you inject it. So if you are preparing for an upcoming surgery, you may need to stop Mounjaro 1 week before the procedure.

5. How long do you have to take Mounjaro?

Like other diabetes medications, Mounjaro is intended for long-term use. So it’s likely you’ll use this medication for several years. And it’s possible that you may need to take it for life.

Type 2 diabetes is a chronic health condition, and there is currently no cure. But using Mounjaro can help manage your blood glucose and reduce the risk of diabetes complications.

It’s common to notice improvements in glucose after a few weeks of starting Mounjaro. If you stop using it, your glucose and A1C levels may return to what they were before you started. If you want or need to stop Mounjaro, speak with your diabetes care team. They can help determine next steps for you to follow.

Will you regain body weight after you stop using Mounjaro?

Yes. If you lost weight while using Mounjaro, it’s likely that you’ll regain some weight if you stop the medication. Studies found that people who stopped using tirzepatide regained an average of 14% of their body weight back during the following year.

6. Is Mounjaro safe to use?

Yes. Mounjaro is considered safe for most people to use for the treatment of Type 2 diabetes. However, be sure to share your full medical history with your diabetes care team prior to starting Mounjaro.

Nausea, diarrhea, and vomiting are common side effects people have when using Mounjaro. Some have also reported constipation, bloating, and burping. Most of these side effects are mild and improve as your body gets used to the medication.

Rarely, people using Mounjaro report these more serious side effects:

• Low blood glucose (hypoglycemia), especially when combined with insulin or other medications that promote insulin release, such as glyburide or glimepiride

• Allergic reactions, including serious reactions such as anaphylaxis

• Kidney damage, particularly if you’re experiencing a lot of vomiting or diarrhea

• Temporary worsening of diabetic retinopathy (an eye condition caused by diabetes)

• Gallbladder disease, including gallstones and inflammation of the the gallbladder

A higher risk of thyroid C-cell tumors was also seen in animal studies of Mounjaro. This hasn’t been seen in human studies. But to be safe, the manufacturer recommends that people with the following conditions shouldn’t use Mounjaro:

• A personal or family history of medullary thyroid cancer

• Multiple endocrine neoplasia type 2 (MEN2) syndrome

Does Mounjaro cause pancreatitis?

No, Mounjaro doesn’t seem to directly cause pancreatitis (swelling of your pancreas). It can, however, cause or contribute to gallbladder disease, which can raise your risk of pancreatitis.

A small number of people using Mounjaro in clinical trials developed pancreatitis. But a similar percentage of people using other diabetes medications or a placebo (an injection with no medication in it) also developed it. Using this evidence, researchers have determined that Mounjaro doesn’t directly cause pancreatitis.

How to save on Mounjaro

There are ways to save on Mounjaro, which is available as a brand-name medication. If you have commercial insurance, you may be eligible to pay as little as $25 per prescription through the manufacturer’s copay savings program.

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Written by:

Kristina D. Carter, PharmD, MBA, MHA

Kristina D. Carter, PharmD, MBA, MHA, has over 25 years of experience working in healthcare. She is registered as a licensed pharmacist in Georgia, Indiana, and Tennessee.

Edited by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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