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Brand names: Mounjaro, Zepbound
Dosage form: Subcutaneous injection (2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg,15 mg per 0.5 mL in single-dose pen)
Drug class: Incretin Mimetics (GLP-1 Agonists)

Medically reviewed by Melisa Puckey, BPharm. Last updated on Mar 28, 2024.

What is tirzepatide?

Tirzepatide is a prescription medicine used for weight loss (Zepbound brand) and type 2 diabetes (Mounjaro brand) in adults. Tirzepatide works for weight loss by decreasing appetite and slowing the movement of food from the stomach into the small intestine, which may make you feel full more quickly and for a longer period of time. In type 2 diabetes, tirzepatide decreases blood sugar levels by increasing insulin production and lowering the amount of sugar the liver makes. Tirzepatide is given as an injection under the skin once a week. Tirzepatide is a GIP and GLP-1 receptor agonist.

Zepbound is FDA-approved for weight loss for adults with obesity or who are overweight and have weight-related medical problems. Zepbound helps you to lose weight and maintain weight loss and should be combined with diet and exercise.

Mounjaro is used to help lower blood sugar in adults with type 2 diabetes; it should be used together with diet and exercise.

When tirzepatide (Mounjaro) is used for type 2 diabetes, it can be used as a single therapy (on its own) or with other diabetes medicines, including sulfonylureas, SGLT2 inhibitors, or metformin.

It is not known if tirzepatide can be used in people who have had pancreatitis. Tirzepatide should not be used in people who have type 1 diabetes.

Mounjaro and Zepbound both contain the same active ingredient, tirzepatide, and are made by Eli Lilly and Company. They are both available as single-dose pens in the same strengths 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg,15 mg per 0.5 mL.

How does tirzepatide work?

Tirzepatide is a GIP and GLP-1 receptor agonist, so it works (mechanism of action) by activating both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) hormone receptors. GLP-1 helps control appetite and calorie intake, and GIP is thought to contribute to regulating food intake as well.

How much weight is lost on Zepbound?

Patients on Zepbound (tirzepatide) 5mg weekly lost 16.1 kg (35.5 lb) on average after 72 weeks. For Zepbound's 10mg weekly dose, the average weight loss was 22.2 kg (48.9 lb), and for Zepbound's 15mg weekly dose average weight loss was 23.6 kg (52.0 lb) over 72 weeks. Patients who used a placebo lost 2.4 kg (5.3 lb) over the 72 weeks. These results are from the clinical trial SURMOUNT-1, NCT04184622.  Individual results may vary. 

What are the side effects of tirzepatide?

Common tirzepatide side effects

The most common tirzepatide side effects include abdominal pain, burping, constipation, diarrhea, dyspepsia, fatigue, gastroesophageal reflux disease, hair loss, hypersensitivity reactions, injection site reactions, nausea, and vomiting, which affects 5% or more patients.

Serious tirzepatide side effects

Stop using this medicine and get emergency medical help if you have:

Call your doctor at once if you have:

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.


Tirzepatide may cause thyroid C-cell tumors. It is important to tell your doctor if you have a personal or your family has a history of thyroid cancer or a condition called Multiple Endocrine Neoplasia (MEN) syndrome. This is a syndrome that causes tumors to develop on endocrine glands. If you experience any of these symptoms: lump or swelling in your neck, difficulty in swallowing, hoarseness, or shortness of breath, then you should call your doctor immediately.

Keep all appointments with your doctor, health professionals, and the laboratory. Your doctor may order certain tests to check your body's response to this medicine.

Before using tirzepatide

How should I use tirzepatide?

You should follow the directions on your prescription label 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 take it more often than prescribed by your doctor.

Tirzepatide is a once-weekly injection given under the skin (subcutaneous) using a pre-filled single-dose pen.

It is usually given

Your doctor will probably start you on a low dose, which may be gradually increased, but not more than once every 4 weeks.

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

You may administer insulin in the same area as tirzepatide, but they should not be given right next to each other. Insulin and tirzepatide should be given as separate injections and not be mixed 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 give Mounjaro, click here: Instructions for Mounjaro

Tirzepatide Dosing information

Usual Zepbound Dose for Weight Loss (Adult)

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

After 4 weeks: The dosage should be increased to 5 mg subcutaneously once a week.

Further dose increases: After at least 4 weeks on the current dose the dosage may be increased in 2.5 mg increments.

Recommended maintenance dose:  5 mg, 10 mg, or 15 mg injected subcutaneously once weekly.

Maximum dose: 15 mg subcutaneously once a week.

Usual Mounjaro Dose for Diabetes Type 2 (Adult)

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

After 4 weeks: The dosage should be increased to 5 mg subcutaneously once a week.

If additional glycemic control is needed: The dosage should be increased 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 of 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 should I do if I miss a dose?

If you miss a dose of tirzepatide take the missed dose as soon as you remember it, if within 4 days after the missed dose. However, if it has been more than 4 days since your last dose, then skip the missed dose and continue your regular dosing schedule. Do not inject two doses within 3 days of each other.

What happens if I 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.


Tell your doctor and pharmacist what prescription and over-the-counter medications, vitamins, nutritional supplements, and herbal products you are planning to take or are taking. They may interact with tirzepatide and 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 this medicine. Your doctor may suggest you use another form of birth control for 4 weeks after starting tirzepatide and for 4 weeks after each dose change.

Taking tirzepatide with other medicines to treat diabetes, such as sulfonylureas or insulin, may increase your risk of hypoglycemia. Talk to your doctor and pharmacist about low blood sugar and how to manage it.

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


What are the ingredients in tirzepatide?

Active ingredient: tirzepatide

Mounjaro 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.

Zepbound 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.


Mounjaro and Zepbound

Eli Lilly and Company.

Marketed by: Lilly USA, LLC Indianapolis, IN 46285, USA.

Popular FAQ

Ozempic, Mounjaro, Wegovy and Zepbound can all lead to long-term weight loss, but only Wegovy and Zepbound are approved by the FDA for this use. In studies, Zepbound has led to a 21% weight loss in adults using the highest dose, while Wegovy has led to about a 15% weight loss. Continue reading

Both tirzepatide and semaglutide are prescription medicines used with diet and exercise to treat people with type 2 diabetes or to help people lose and maintain weight loss. Semaglutide has also been approved for cardiovascular risk reduction. They are marketed as Ozempic, Wegovy and Rybelsus (semaglutide) and as Mounjaro or Zepbound (tirzepatide). Continue reading

Some pharmacies or clinics may supply compounded versions of medicines like tirzepatide (Mounjaro, Zepbound) and semaglutide (Ozempic, Wegovy) to patients, but the FDA has issued safety warnings about this practice. Concerns have risen over active ingredients, side effects and labeling of these compounded products. Continue reading

Mounjaro's active ingredient has been shown to help with weight loss when used to treat obese patients. Mounjaro's active ingredient tirzepatide is approved for weight loss but under the brand name Zepbound, in studies participants treated with Mounjaro's active ingredient tirzepatide lost between 16.1 kg (35.5 lb) and 23.6 kg (52.0 lb) on average over 72 weeks. Continue reading

The specific amount of weight you might lose from Zepbound is uncertain, but significant weight loss ranging from 35.5 lb (16.1 kg) to 52.0 lb (23.6 kg) was observed in the 72-week SURMOUNT-1 clinical trial, which compared different Zepbound (tirzepatide) doses to a placebo (inactive treatment). Continue reading

Zepbound is administered once a week by subcutaneous (under the skin) injection. Your healthcare provider will show you how to do this and then you can administer the injection at home yourself or have a caregiver administer it for you. Your healthcare provider will tell you the correct dose of Zepbound to use. Continue reading

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Further information

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