Pronunciation: mown-JAHR-OH
Generic name: tirzepatide
Dosage form: single-dose injection pen (multiple strengths), single-dose vial (multiple strengths)
Drug class: GLP-1 Agonists (Incretin Mimetics)

Medically reviewed by Carmen Pope, BPharm. Last updated on May 14, 2025.

What is Mounjaro?

Mounjaro (tirzepatide) is used for type 2 diabetes to help lower blood sugar levels, and tirzepatide also causes weight loss. Mounjaro is a once-weekly injection that should be used alongside dietary changes and exercise.

Mounjaro received FDA approval on May 13, 2022. There is no Mounjaro generic. The 2 different brands of tirzepatide (Mounjaro and Zepbound) are made by Eli Lilly and Company but are FDA-approved for different conditions.

• Mounjaro: Specifically approved for type 2 diabetes management in adults.
• Zepbound: Designated for weight loss treatment in adults.
• See Zepbound vs Mounjaro: Complete Comparison Guide for Weight Loss and Diabetes Treatment.

Benefits of Mounjaro

• Blood sugar control and HbA1c reduction.*
• Significant weight loss support.**

*HbA1c measures your average blood sugar level over the past 2-3 months.
** Not an FDA-approved use.

Although Mounjaro for weight loss is not officially approved, Mounjaro has been shown to help weight loss and maintain the lost weight in clinical trials when combined with diet and exercise. 

Weight loss support

The most recent clinical trial (Surmount-5) comparing tirzepatide (Zepbound, Mounjaro) to semaglutide (Ozempic, Wegovy) reported that tirzepatide is significantly more effective than semaglutide.

• Average weight loss: tirzepatide 50.3 lb (22.8 kg), semaglutide 33.1 lb (15 kg).
• Percentage of body weight lost: tirzepatide 20.2%, semaglutide 13.7%.
• Waist circumference reduction: tirzepatide 7.2" (18.4 cm), semaglutide 5.1" (13 cm).

Tirzepatide is probably more effective than semaglutide because of its dual mechanism of action.

How does Mounjaro work?

Mounjaro (tirzepatide) has a dual mechanism of action and activates two hormone receptors in the gut: GIP (gastric inhibitory polypeptide) and GLP-1 (glucagon-like peptide-1). This:

• Stimulates insulin release from the pancreas when blood glucose is elevated
• Decreases glucagon secretion (a hormone that raises blood sugar)
• Slows down stomach emptying, which helps to control post-meal blood sugar spikes
• Helps to control appetite and food intake
• Increases feelings of fullness and satiety, acting on GLP-1 receptors in the brain
• Affects the brain's reward pathways, with potential benefits beyond diabetes and weight management.

Mounjaro belongs to the drug class called GIP receptor and GLP-1 receptor agonists. 

Medical uses and FDA approvals

Mounjaro is approved by the FDA for blood sugar (glucose) control in adults with type 2 diabetes, along with diet and exercise.

WARNING: Mounjaro is not approved for type 1 diabetes treatment, and it is not known if it can be used in people with pancreatitis.

It is not known if Mounjaro is safe or effective in children under 18 years of age.

Side effects

The most common side effects of Mounjaro include:

• nausea
• diarrhea
• decreased appetite
• vomiting
• constipation
• indigestion
• stomach (abdominal) pain.

Serious side effects and warnings

Mounjaro may cause the following serious side effects:

• Possible thyroid tumors, including cancer. Tell your healthcare provider if you get a lump or swelling in your neck, hoarseness, trouble swallowing, or shortness of breath. These may be symptoms of thyroid cancer. In studies with rats, Mounjaro and medicines that work like Mounjaro caused thyroid tumors, including thyroid cancer. It is not known if Mounjaro will cause thyroid tumors, or a type of thyroid cancer called medullary thyroid carcinoma (MTC) in people.

Do not use Mounjaro if you or any of your family have ever had a type of thyroid cancer called medullary thyroid carcinoma (MTC), or if you have an endocrine system condition called Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

• Inflammation of your pancreas (pancreatitis). Stop using Mounjaro and call your healthcare provider right away if you have severe pain in your stomach area (abdomen) that will not go away, with or without vomiting. You may feel the pain from your abdomen to your back.
• Low blood sugar (hypoglycemia). Your risk for getting low blood sugar may be higher if you use Mounjaro with another medicine that can cause low blood sugar, such as a sulfonylurea or insulin. Signs and symptoms of low blood sugar may include:
  • dizziness or light-headedness
  • sweating
  • confusion or drowsiness
  • headache
  • blurred vision
  • slurred speech
  • shakiness
  • fast heartbeat
  • anxiety, irritability, or mood changes
  • hunger
  • weakness
  • feeling jittery
• Serious allergic reactions. Stop using Mounjaro and get medical help right away if you have any symptoms of a serious allergic reaction, such as:
  • swelling of your face, lips, tongue, or throat
  • problems breathing or swallowing
  • severe rash or itching
  • fainting or feeling dizzy
  • very rapid heartbeat.
• Kidney problems (kidney failure). In people who have kidney problems, diarrhea, nausea, and vomiting may cause a loss of fluids (dehydration), which may cause kidney problems to get worse. You need to drink fluids to help reduce your chance of dehydration.
• Severe stomach problems. Stomach problems, sometimes severe, have been reported in people who use Mounjaro. Tell your healthcare provider if you have stomach problems that are severe or will not go away.
• Vision changes. Tell your healthcare provider if you have changes in vision during treatment with Mounjaro.
• Gallbladder problems. Gallbladder problems have occurred in some people who use Mounjaro. Tell your healthcare provider right away if you get symptoms of gallbladder problems, which may include:
  • pain in your upper stomach (abdomen)
  • fever
  • yellowing of skin or eyes (jaundice)
  • clay-colored stools.
• Food or liquid getting into the lungs during surgery or other procedures that use anesthesia or deep sleepiness (deep sedation). Mounjaro may increase the chance of food getting into your lungs during surgery or other procedures. Tell all your healthcare providers that you are taking Mounjaro before you are scheduled to have surgery or other procedures.

Talk to your healthcare provider if you have any side effect that bothers you or that does not go away. These are not all the possible side effects of Mounjaro. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Related/similar drugs

Before using this medicine

You should not use this medicine if you:

• are allergic to the tirzepatide, Mounjaro, Zepbound, or any of the ingredients contained in the pens or vials (see below for a list of ingredients)
• have a personal or family history of medullary thyroid carcinoma (a type of thyroid cancer); or
• have multiple endocrine neoplasia type 2 (tumors in your glands).

Tell your doctor if you have ever had:

• pancreas problems;
• kidney disease;
• are planning surgery or a procedure that uses anesthesia or deep sedation
• a severe stomach problem, such as problems with digesting food or slowed emptying of your stomach (gastroparesis); or
• diabetic retinopathy (a diabetes complication that affects the eyes).

Pregnancy

Tell your healthcare provider if you are pregnant, you become pregnant, or plan to become pregnant while using this medicine. It is not known if this medicine will harm your unborn baby.

This medicine can make birth control pills less effective. Ask your doctor about other birth control options such as an injection, implant, skin patch, vaginal ring, condom, diaphragm, cervical cap, or contraceptive sponge. If you take birth control pills, you may need to use additional birth control methods for 4 weeks after starting this medicine, and for 4 weeks each time the dose is increased.

Breastfeeding

Tell your healthcare provider if you are breastfeeding or plan to breastfeed while using this medicine. It is not known whether this tirzepatide passes into your breast milk. Talk to your healthcare provider about the best way to feed your baby while using this medicine.

How should I use Mounjaro?

You should read the Instructions for Use carefully and ask your pharmacist or doctor to explain any part you do not understand. It is important to use this medicine exactly as directed. Do not take more or less of it or more often than your doctor prescribes.

Mounjaro is a pre-filled pen injected under the skin (subcutaneously).

• Mounjaro is usually given 1 time a week
• It can be given with or without meals at any time of the day
• It may be injected under the skin of the thigh, abdomen, or upper arm.
  • You should rotate the injection site for each dose.
  • See Where is the best place to inject Mounjaro? for more information.

Your healthcare provider will usually start you on a low dose, which will be gradually increased, but not more than once every 4 weeks.

You may change the day of the week you use this medicine as long as there are at least three days between doses.

You may give insulin in the same area as this medicine, but they should not be given right next to each other. Do not mix insulin and Mounjaro in the same injection.

Mounjaro controls type 2 diabetes but does not cure it. It may take four weeks or longer before you see the full benefit of this medicine. Continue to take this medicine even if you feel well. Do not stop taking this medicine without talking to your doctor.

For more detailed instructions with diagrams, on how to use this medicine, click here: Instructions for Mounjaro.

Mounjaro Dosing Information

Usual Adult Dose for Diabetes Type 2:

Initial dose: 2.5 mg under the skin (subcutaneously) once a week.

After 4 weeks: Increase to 5 mg subcutaneously once a week.

If additional glycemic control is needed: Increase from 5 mg to 7.5 mg for 4 weeks and thereafter in 2.5 mg increments after at least 4 weeks on the current dose.

Maximum dose: 15 mg subcutaneously once a week.

Comments: The 2.5 mg dosage is for starting treatment and is not intended for glycemic control. The day of weekly administration can be changed, if necessary, as long as the time between the 2 doses is at least 3 days (72 hours).

What strengths are Mounjaro pens?

Mounjaro is available as a single-dose autoinjector pen or vial in the following strengths:

• 2.5 mg/0.5 mL 
• 5 mg/0.5 mL 
• 7.5 mg/0.5 mL 
• 10 mg/0.5 mL 
• 12.5 mg/0.5 mL 
• 15 mg/0.5 mL.

In the past, there have been issues with Mounjaro availability due to increased demand leading to drug shortages for some strengths.

What should I do if I miss a dose?

Take the missed dose as soon as you remember it within 4 days after the missed dose.

However, if more than 4 days have passed, skip the missed dose and continue your regular dosing schedule. Do not inject two doses within 3 days of each other.

What should I do in case of an overdose?

In case of overdose, call the poison control helpline at 1-800-222-1222. Information is also available online at Poison Help If the victim has collapsed, had a seizure, has trouble breathing, or can't be awakened, immediately call emergency services at 911.

What other drugs affect Mounjaro?

Tell your doctor and pharmacist what prescription and nonprescription medications, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Your doctor may need to change the doses of your medications or monitor you carefully for side effects.

Birth control pills may not work as well while receiving Mounjaro. Your doctor may suggest you use another form of birth control for 4 weeks after starting this medicine and for 4 weeks after each dose change.

Taking other medicines to treat diabetes like insulin, sulfonylureas, or other GLP-1 agonists such as Ozempic (see Mounjaro vs Ozempic) with this treatment may increase your risk of low blood sugar levels. Talk to your doctor and pharmacist about low blood sugar and how to manage it.

This medicine delays gastric emptying and has the potential to change the absorption of other medicines that are taken orally.

This list is not complete. Many other drugs may interact with this medicine, including prescription and over-the-counter medicines, vitamins, and herbal products. To check for interactions with this medicine click the link below.

How do I store Mounjaro?

Store your Mounjaro pens in the refrigerator between 36⁰F to 46⁰F (2⁰C to 8⁰C) in their original carton to protect them from light.

If needed, or while traveling, each single-dose Mounjaro pen can be stored at room temperature up to 86⁰F (30⁰C) for up to 21 days.

Mounjaro ingredients

Active ingredient: tirzepatide

Inactive ingredients: sodium chloride, sodium phosphate dibasic heptahydrate, and water for injection. Hydrochloric acid solution and/or sodium hydroxide solution may have been added to adjust the pH.

Who makes Mounjaro?

Mounjaro is made by Eli Lilly and Company, commonly known as Lilly. They are an American pharmaceutical company based in Indianapolis that was founded in 1876. Notable drugs from Lilly include:

• Zepbound (tirzepatide for weight loss - same molecule as Mounjaro)
• Trulicity (diabetes)
• Verzenio (breast cancer)
• Jardiance (diabetes, heart failure - partnered with Boehringer Ingelheim)
• Cymbalta (depression, anxiety)
• Prozac (depression - though now generic)
• Olumiant (rheumatoid arthritis)
• Donanemab (Alzheimer's - recently approved).

Popular FAQ

More FAQ

• Mounjaro side effects you need to be aware of

View more FAQ

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Medical Disclaimer