Mounjaro (Tirzepatide)
Dual GIP/GLP-1 Receptor Agonist for Type 2 Diabetes and Weight Management
Quick Facts About Mounjaro
Key Takeaways About Mounjaro
- First-in-class dual action: Mounjaro is the first approved medicine that activates both GIP and GLP-1 receptors, providing superior blood sugar control and weight loss compared to single-receptor agonists
- Once-weekly injection: Administered subcutaneously once per week at any time of day, with or without food, making it convenient for long-term use
- Significant weight loss: In clinical trials, the highest dose (15 mg) led to an average weight loss of 22.5% of body weight over 72 weeks for weight management
- Common GI side effects: Nausea, diarrhoea, and vomiting are the most frequent side effects but typically improve over time as the body adjusts
- Gradual dose escalation: Treatment starts at 2.5 mg weekly and increases in 2.5 mg increments every 4 weeks to minimise gastrointestinal side effects
What Is Mounjaro and What Is It Used For?
Mounjaro (tirzepatide) is a dual GIP/GLP-1 receptor agonist used to treat type 2 diabetes in adults and children aged 10 and older, and for chronic weight management in adults with obesity or overweight with at least one weight-related health condition.
Mounjaro contains the active substance tirzepatide, a synthetic peptide that simultaneously activates two incretin hormone receptors: glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1). This dual mechanism of action distinguishes tirzepatide from other incretin-based therapies that target only the GLP-1 receptor, and it has demonstrated superior efficacy in both glycaemic control and weight reduction in head-to-head clinical trials.
In patients with type 2 diabetes, Mounjaro lowers blood sugar by stimulating insulin secretion and suppressing glucagon release, both in a glucose-dependent manner. This means the drug's effects are strongest when blood sugar levels are elevated and diminish as levels normalise, significantly reducing the risk of hypoglycaemia when used without insulin or sulfonylureas. Mounjaro also slows gastric emptying, which contributes to reduced post-meal blood sugar spikes and decreased appetite.
For weight management, Mounjaro is approved for adults with a body mass index (BMI) of 30 kg/m² or greater (obesity), or a BMI of 27 kg/m² or greater (overweight) with at least one weight-related comorbidity such as prediabetes, type 2 diabetes, high blood pressure, dyslipidaemia, obstructive sleep apnoea (OSA), or a history of cardiovascular events. Tirzepatide affects appetite regulation centres in the brain, helping patients eat less and feel fuller sooner. In the landmark SURMOUNT-1 clinical trial, participants taking tirzepatide 15 mg achieved an average weight loss of 22.5% of their body weight over 72 weeks.
In patients with obstructive sleep apnoea (OSA) and obesity, Mounjaro can be used with or without continuous positive airway pressure (CPAP) therapy. Weight loss achieved with tirzepatide has been shown to reduce the severity of OSA symptoms, including reducing the apnoea-hypopnoea index (AHI), which measures the number of breathing interruptions during sleep.
Mounjaro can be used as monotherapy when metformin is not tolerated or is contraindicated, or in combination with other diabetes medications including metformin, sulfonylureas, SGLT2 inhibitors, and insulin. When used alongside insulin or sulfonylureas, the doses of these medications may need to be reduced to prevent hypoglycaemia.
Mounjaro was first approved by the US Food and Drug Administration (FDA) in May 2022 for type 2 diabetes, and subsequently by the European Medicines Agency (EMA). It received FDA approval for chronic weight management in November 2023 under the brand name Zepbound. The active ingredient tirzepatide has been studied in over 20,000 patients across the SURPASS (diabetes) and SURMOUNT (weight management) clinical trial programmes.
What Should You Know Before Taking Mounjaro?
Before starting Mounjaro, inform your doctor about all your medical conditions, particularly any history of pancreatitis, gastroparesis, thyroid cancer, or diabetic retinopathy. Do not use Mounjaro if you are allergic to tirzepatide.
Contraindications
You should not use Mounjaro if any of the following apply to you:
- Allergy to tirzepatide or any of the other ingredients in Mounjaro (dibasic sodium phosphate heptahydrate, sodium chloride, sodium hydroxide, hydrochloric acid, water for injections)
- Personal or family history of medullary thyroid carcinoma (MTC) – in animal studies, GLP-1 receptor agonists caused thyroid C-cell tumours; while this has not been confirmed in humans, Mounjaro should not be used in patients at risk
- Multiple Endocrine Neoplasia syndrome type 2 (MEN 2) – a condition that increases the risk of medullary thyroid cancer
Warnings and Precautions
Talk to your doctor, pharmacist, or nurse before using Mounjaro if you have or have had any of the following conditions:
- Pancreatitis – if you have a history of inflammation of the pancreas, Mounjaro should be used with caution. Seek immediate medical attention if you experience severe, persistent abdominal pain that may radiate to the back, with or without vomiting
- Gastroparesis or severe digestive problems – Mounjaro slows gastric emptying, which can worsen conditions where food remains in the stomach longer than normal
- Diabetic retinopathy or macular oedema – rapid improvements in blood sugar control have been associated with worsening diabetic eye disease in some patients. Your doctor may recommend eye examinations before and during treatment
- Use of insulin or sulfonylureas – combining Mounjaro with these medications increases the risk of hypoglycaemia (low blood sugar). Your doctor may need to adjust the doses of these medications
- Kidney disease – gastrointestinal side effects such as vomiting and diarrhoea can cause dehydration, which may worsen kidney function. It is important to drink plenty of fluids during treatment
If you are scheduled for surgery under general anaesthesia, inform your doctor and the anaesthesia team that you are taking Mounjaro. Because tirzepatide slows gastric emptying, there is a risk that stomach contents may not have fully emptied before the procedure, increasing the risk of aspiration. Your doctor may advise you to temporarily stop Mounjaro before surgery.
Use in Children and Adolescents
Mounjaro is approved for children aged 10 years and older for the treatment of type 2 diabetes. It has been studied only in children and adolescents with type 2 diabetes who were overweight or had obesity at the start of treatment. The dosing schedule for children is similar to adults, starting at 2.5 mg weekly with increases up to a maximum of 10 mg weekly.
Mounjaro is not recommended for children under 10 years of age with type 2 diabetes, or for children and adolescents under 18 years for weight management, as it has not been studied in these populations. If you are under 18 years old, a caregiver may assist with administering the injection, or you may self-inject if your doctor deems it appropriate.
Pregnancy and Breastfeeding
Mounjaro should not be used during pregnancy. The effects of tirzepatide on an unborn baby are unknown, and animal studies are insufficient to rule out potential harm. If you are pregnant, think you might be pregnant, or are planning to become pregnant, tell your doctor before using this medicine. Reliable contraception is recommended during treatment with Mounjaro.
It is not known whether tirzepatide passes into breast milk. A risk to the newborn or infant cannot be excluded. If you are breastfeeding or planning to breastfeed, discuss with your doctor whether to discontinue breastfeeding or to delay treatment with Mounjaro. Your doctor will help you decide based on the benefits of treatment versus the potential risks to your baby.
Driving and Operating Machinery
Mounjaro is unlikely to affect your ability to drive or use machines. However, if you are taking Mounjaro in combination with a sulfonylurea or insulin, you may experience low blood sugar (hypoglycaemia), which can impair your concentration and reaction time. Signs of low blood sugar include headache, drowsiness, weakness, dizziness, hunger, confusion, irritability, rapid heartbeat, and sweating. Avoid driving or operating machinery if you experience these symptoms.
Sodium Content
Mounjaro contains less than 1 mmol (23 mg) sodium per dose, meaning it is essentially sodium-free. This is relevant for patients on a sodium-restricted diet.
How Does Mounjaro Interact with Other Drugs?
Mounjaro can interact with oral medications because it slows gastric emptying, potentially altering the absorption of other drugs. The most clinically significant interactions are with insulin, sulfonylureas, and oral contraceptives.
Because tirzepatide delays gastric emptying, it can affect how quickly other orally administered medicines are absorbed. This is particularly relevant during the initial weeks of treatment and following dose increases. In most cases, this effect is modest and does not require dose adjustments for co-administered medications. However, for medications with a narrow therapeutic index (where small changes in blood levels can have significant consequences), close monitoring may be warranted.
Clinical pharmacology studies have shown that tirzepatide does not have clinically meaningful effects on the pharmacokinetics of metformin, digoxin, lisinopril, atorvastatin, or acetaminophen (paracetamol) at steady state. However, during the dose-escalation phase, transient changes in absorption may occur. Patients taking time-sensitive medications should discuss the timing of their doses with their healthcare provider.
Major Interactions
| Drug | Effect | Action Required |
|---|---|---|
| Insulin | Increased risk of hypoglycaemia due to additive blood sugar-lowering effects | Doctor should reduce insulin dose when starting Mounjaro; monitor blood glucose closely |
| Sulfonylureas (glimepiride, glipizide, glyburide) | Increased risk of hypoglycaemia | Doctor may reduce sulfonylurea dose; frequent blood glucose monitoring recommended |
| Oral contraceptives | Delayed gastric emptying may reduce absorption, potentially lowering contraceptive efficacy | Consider switching to a non-oral contraceptive method or adding a barrier method during initial treatment |
| Warfarin | Potential changes in warfarin absorption and INR values | Monitor INR more frequently when starting Mounjaro or changing the dose |
Minor Interactions and Monitoring
| Drug | Effect | Clinical Significance |
|---|---|---|
| Metformin | No clinically meaningful interaction at steady state | Safe to combine; no dose adjustment needed |
| SGLT2 inhibitors (empagliflozin, dapagliflozin) | Additive blood sugar-lowering; dehydration risk may increase | Monitor for dehydration; maintain adequate fluid intake |
| Statins (atorvastatin) | No clinically relevant pharmacokinetic interaction | Safe to combine; no dose adjustment needed |
| Paracetamol (acetaminophen) | Slightly delayed absorption during dose escalation | Minimal clinical impact; no dose adjustment needed |
| Digoxin | No clinically meaningful interaction observed | Safe to combine; standard monitoring recommended |
Always inform your doctor, pharmacist, or nurse about all medications you are taking, including prescription drugs, over-the-counter medicines, vitamins, and herbal supplements. This is essential to ensure safe and effective treatment with Mounjaro.
What Is the Correct Dosage of Mounjaro?
Mounjaro is started at 2.5 mg once weekly for 4 weeks, then increased to 5 mg weekly. The dose can be further increased in 2.5 mg increments every 4 weeks up to a maximum of 15 mg once weekly for adults, or 10 mg for children aged 10–17 with type 2 diabetes.
Always use Mounjaro exactly as your doctor has prescribed. The dose is gradually increased (titrated) over several weeks to reduce the likelihood and severity of gastrointestinal side effects. Do not change your dose unless your doctor instructs you to do so. Each vial contains a single dose of 0.5 ml solution.
Adults
Adult Dosage Schedule – Type 2 Diabetes and Weight Management
| Period | Dose | Purpose |
|---|---|---|
| Weeks 1–4 | 2.5 mg once weekly | Starting dose (not a therapeutic dose) |
| Weeks 5–8 | 5 mg once weekly | First therapeutic dose |
| Weeks 9–12 | 7.5 mg once weekly | If additional efficacy needed |
| Weeks 13–16 | 10 mg once weekly | Further dose increase if needed |
| Weeks 17–20 | 12.5 mg once weekly | Further dose increase if needed |
| Week 21 onwards | 15 mg once weekly | Maximum dose |
Your doctor will instruct you to remain on each dose for at least 4 weeks before increasing to the next level. Not all patients will need to reach the maximum dose – your doctor will determine the optimal dose based on your blood sugar levels, weight loss goals, and tolerability.
Children and Adolescents (aged 10–17 years)
Paediatric Dosage Schedule – Type 2 Diabetes Only
The starting dose is 2.5 mg once weekly for 4 weeks, increasing to 5 mg once weekly. If needed, the dose may be further increased in 2.5 mg increments to 7.5 mg and then to a maximum of 10 mg once weekly. Each dose level should be maintained for at least 4 weeks before increasing. A caregiver may administer the injection, or the child may self-inject if deemed appropriate by the prescribing doctor.
Elderly Patients
No dose adjustment is required based on age alone. However, elderly patients may be more susceptible to gastrointestinal side effects and dehydration. Careful monitoring and adequate fluid intake are recommended, especially during dose escalation. If kidney function is reduced, your doctor will consider this when determining the appropriate dose.
How to Inject Mounjaro
Mounjaro is injected under the skin (subcutaneously) in the abdomen, upper thigh, or back of the upper arm. You should rotate injection sites within the same area each week and never inject directly into a vein. If you also use insulin, choose a different injection site. Each vial is for single use only.
Before injecting, check that the solution is clear and colourless to slightly yellow. Do not use if it is frozen, cloudy, or contains particles. Wash your hands thoroughly, clean the vial stopper with an antiseptic swab, draw up the full 0.5 ml dose using a sterile syringe and needle, and inject under the skin. Hold the needle in place for 5 seconds to ensure the full dose is delivered. Dispose of the vial, needle, and syringe in a sharps container immediately after use.
You may inject Mounjaro at any time of day, with or without food. Try to inject on the same day each week. If you need to change your injection day, the interval between two doses must be at least 3 days. Once you have selected a new day, continue dosing once weekly on that new day.
Missed Dose
If you forget to inject a dose of Mounjaro:
- If 4 days or less have passed since the missed dose: inject it as soon as you remember, then continue with your regular schedule
- If more than 4 days have passed: skip the missed dose entirely and inject your next dose on the regularly scheduled day
- Never inject a double dose to make up for a missed one. The minimum interval between two doses must be at least 3 days
Overdose
If you have used too much Mounjaro, contact your doctor immediately. An overdose may cause hypoglycaemia (low blood sugar), nausea, and vomiting. There is no specific antidote; treatment is supportive and based on the patient's symptoms. If you experience symptoms of severe hypoglycaemia (confusion, seizures, loss of consciousness), seek emergency medical care immediately.
Do not stop using Mounjaro without first talking to your doctor. If you stop using Mounjaro and you have type 2 diabetes, your blood sugar levels may rise. If you are using Mounjaro for weight management, you may regain weight after discontinuation.
What Are the Side Effects of Mounjaro?
Like all medicines, Mounjaro can cause side effects, although not everyone gets them. The most common side effects are gastrointestinal – nausea, diarrhoea, and vomiting – which typically improve over time. Serious but rare side effects include pancreatitis and severe allergic reactions.
Gastrointestinal side effects are the most frequently reported adverse reactions with tirzepatide. They are most common at the start of treatment and after each dose increase, and they usually diminish as your body adjusts to the medication. The gradual dose-escalation schedule (starting at 2.5 mg) is specifically designed to minimise these effects. If gastrointestinal symptoms are severe or persistent, contact your doctor, who may recommend temporarily pausing the dose escalation or reducing the dose.
Severe, persistent abdominal pain radiating to the back (possible pancreatitis), difficulty breathing, rapid swelling of the face, lips, tongue, or throat (severe allergic reaction/anaphylaxis), or signs of severe hypoglycaemia such as confusion, seizures, or loss of consciousness.
Very Common
May affect more than 1 in 10 people
- Nausea
- Diarrhoea
- Abdominal pain (particularly in weight management and paediatric patients)
- Vomiting (particularly in weight management and paediatric patients)
- Constipation (in weight management patients)
- Hypoglycaemia (when used with sulfonylureas or insulin)
Common
May affect up to 1 in 10 people
- Hypoglycaemia (when used with metformin and SGLT2 inhibitors, or metformin alone in children)
- Allergic reactions (rash, itching, eczema)
- Dizziness (particularly in weight management patients)
- Low blood pressure (in weight management patients)
- Decreased appetite (in diabetes patients)
- Indigestion (dyspepsia)
- Bloating and flatulence
- Belching (eructation)
- Acid reflux (gastro-oesophageal reflux disease)
- Hair loss (in weight management patients)
- Fatigue
- Injection site reactions (itching, redness)
- Increased heart rate
- Increased pancreatic enzyme levels (lipase, amylase)
- Elevated calcitonin levels (in weight management patients)
Uncommon
May affect up to 1 in 100 people
- Acute pancreatitis (inflammation of the pancreas)
- Hypoglycaemia (when used with metformin alone in adults)
- Gallstones (cholelithiasis)
- Inflammation of the gallbladder (cholecystitis)
- Weight loss (in diabetes patients, as a side effect)
- Injection site pain
- Elevated calcitonin levels (in diabetes and OSA patients)
- Change in taste perception
- Change in skin sensation
- Delayed gastric emptying
Rare
May affect up to 1 in 1,000 people
- Severe allergic reactions (anaphylaxis, angioedema)
If you experience persistent vomiting, diarrhoea, or nausea that leads to dehydration (symptoms include dark urine, dizziness, and dry mouth), drink plenty of fluids and contact your doctor. Dehydration can lead to reduced kidney function, particularly in patients with pre-existing kidney disease.
Hypoglycaemia is very common when Mounjaro is combined with insulin or sulfonylureas. Symptoms include headache, drowsiness, weakness, dizziness, hunger, confusion, irritability, rapid heartbeat, and sweating. Your doctor should advise you on how to treat low blood sugar and may need to reduce the dose of your insulin or sulfonylurea.
If you experience any side effects, including any not listed above, talk to your doctor, pharmacist, or nurse. You can also report side effects directly to your national pharmacovigilance authority to help continuously monitor the benefit-risk balance of this medicine.
How Should You Store Mounjaro?
Store Mounjaro in a refrigerator at 2–8°C. Do not freeze. If needed, it can be kept at room temperature (up to 30°C) for a maximum of 21 days, after which it must be discarded.
Proper storage of Mounjaro is essential to maintain its effectiveness and safety. Keep the medicine out of the sight and reach of children. Do not use Mounjaro after the expiry date printed on the label and carton (the expiry date refers to the last day of that month).
- Refrigerate at 2°C to 8°C – store in the original packaging to protect from light
- Do not freeze – if the vial has been frozen, it must NOT be used
- Room temperature storage – Mounjaro can be stored at up to 30°C for a maximum of 21 days total. After 21 days at room temperature, the vial must be discarded even if it has not been opened
- Do not use if the vial, seal, or rubber stopper is damaged, or if the solution is cloudy, discoloured, or contains visible particles
Do not dispose of Mounjaro in household waste or down the drain. Ask your pharmacist for guidance on how to properly dispose of unused medicines. These measures help protect the environment.
What Does Mounjaro Contain?
The active substance in Mounjaro is tirzepatide. Each vial contains a single dose of tirzepatide in 0.5 ml of solution for injection, available in six strengths from 2.5 mg to 15 mg.
| Strength | Tirzepatide per Vial | Volume |
|---|---|---|
| Mounjaro 2.5 mg | 2.5 mg | 0.5 ml |
| Mounjaro 5 mg | 5 mg | 0.5 ml |
| Mounjaro 7.5 mg | 7.5 mg | 0.5 ml |
| Mounjaro 10 mg | 10 mg | 0.5 ml |
| Mounjaro 12.5 mg | 12.5 mg | 0.5 ml |
| Mounjaro 15 mg | 15 mg | 0.5 ml |
Inactive Ingredients
The other ingredients (excipients) in Mounjaro are:
- Dibasic sodium phosphate heptahydrate
- Sodium chloride
- Sodium hydroxide (for pH adjustment)
- Concentrated hydrochloric acid (for pH adjustment)
- Water for injections
Mounjaro contains less than 1 mmol (23 mg) sodium per dose, meaning it is essentially sodium-free.
Appearance and Packaging
Mounjaro is a clear, colourless to slightly yellow solution for injection supplied in single-use glass vials. Each vial contains 0.5 ml of solution. Needles and syringes are not included in the packaging and must be obtained separately. Packs are available containing 1, 4, or 12 vials, as well as multipacks of 4 or 12 vials. Not all pack sizes may be available in your country.
The marketing authorisation holder is Eli Lilly Nederland B.V., Utrecht, the Netherlands. The medicine is manufactured by Eli Lilly Italia S.p.A., Sesto Fiorentino, Florence, Italy.
Frequently Asked Questions About Mounjaro
Mounjaro (tirzepatide) and Ozempic (semaglutide) are both injectable medications used for type 2 diabetes and weight management, but they differ in their mechanism of action. Mounjaro activates both GIP and GLP-1 receptors (dual agonist), while Ozempic targets only the GLP-1 receptor. Head-to-head clinical trials (SURPASS-2) showed that tirzepatide produced greater reductions in HbA1c and body weight compared to semaglutide 1 mg. Both are administered once weekly by subcutaneous injection.
In the SURMOUNT-1 clinical trial involving adults with obesity or overweight, participants taking tirzepatide 15 mg lost an average of 22.5% of their body weight over 72 weeks (approximately 24 kg or 52 lbs). Those on 10 mg lost 21.4%, and those on 5 mg lost 16.0%, compared to 2.4% with placebo. Individual results vary based on starting weight, dose, diet, physical activity, and adherence to treatment. Mounjaro should be used in combination with a reduced-calorie diet and increased physical activity.
There is no direct pharmacological interaction between Mounjaro and alcohol. However, alcohol can independently lower blood sugar levels, which may increase the risk of hypoglycaemia, particularly if you are also taking insulin or sulfonylureas alongside Mounjaro. Alcohol can also worsen gastrointestinal side effects such as nausea and vomiting. If you choose to drink alcohol, do so in moderation and monitor your blood sugar levels carefully. Consult your doctor for personalised advice.
If you stop taking Mounjaro, your blood sugar levels may rise again if you have type 2 diabetes, and you may regain weight that you previously lost. The SURMOUNT-1 trial extension data showed that participants who discontinued tirzepatide regained approximately two-thirds of their lost weight within one year of stopping. Do not stop Mounjaro without first discussing with your doctor, who can help plan a safe transition and advise on alternative treatments if needed.
Mounjaro has been studied in clinical trials lasting up to 2 years, during which it maintained its efficacy and safety profile. However, as a relatively new medication (first approved in 2022), long-term data beyond 2 years are still being collected through ongoing post-marketing surveillance and extension studies. The most common long-term concerns include gastrointestinal tolerability, potential pancreatic effects, and thyroid safety (based on animal data). Your doctor will regularly monitor your health during treatment. Report any new or worsening symptoms promptly.
No. Mounjaro is not approved for type 1 diabetes and should not be used as a substitute for insulin in people whose bodies cannot produce insulin. Tirzepatide works by enhancing insulin secretion from functioning pancreatic beta cells, which are absent or severely depleted in type 1 diabetes. Using Mounjaro in type 1 diabetes could lead to diabetic ketoacidosis, a potentially life-threatening condition. Always use only medications prescribed specifically for your condition.
References
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. 2022;387(3):205-216. doi:10.1056/NEJMoa2206038 (SURMOUNT-1 trial)
- Frías JP, Davies MJ, Rosenstock J, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine. 2021;385(6):503-515. doi:10.1056/NEJMoa2107519 (SURPASS-2 trial)
- European Medicines Agency (EMA). Mounjaro (tirzepatide) – Summary of Product Characteristics. Last updated January 2026.
- American Diabetes Association (ADA). Standards of Care in Diabetes – 2024. Diabetes Care. 2024;47(Supplement 1):S1-S321.
- Davies MJ, Aroda VR, Collins BS, et al. Management of Hyperglycaemia in Type 2 Diabetes, 2022. A Consensus Report by the American Diabetes Association (ADA) and the European Association for the Study of Diabetes (EASD). Diabetologia. 2022;65(12):1925-1966.
- World Health Organization (WHO). Obesity and Overweight Fact Sheet. 2024.
- National Institute for Health and Care Excellence (NICE). Tirzepatide for treating type 2 diabetes. Technology appraisal guidance [TA924]. 2023.
- US Food and Drug Administration (FDA). Highlights of Prescribing Information – Mounjaro (tirzepatide) injection. Revised 2024.
Editorial Team
iMedic Medical Review Board – Board-certified endocrinologists and clinical pharmacologists
Level 1A – Based on systematic reviews and randomised controlled trials (SURPASS, SURMOUNT programmes)
ADA Standards of Care, EASD/ADA Consensus Report, NICE Guidelines, EMA SmPC, WHO recommendations
No pharmaceutical funding or sponsorship. Independent medical editorial content with no conflicts of interest.
This article was last medically reviewed on . All medical information is based on current evidence-based guidelines and peer-reviewed research. For questions about this content, contact our editorial team.