Your Complete Guide To Mounjaro

Looking for extra support to reach your weight loss goals? Many treatments can help you lose weight safely and sustainably, and Mounjaro is one of them. Mounjaro is a dual GLP-1/GIP receptor agonist, designed to treat obesity or to help those who are overweight in the presence of other weight-related health conditions. It contains tirzepatide, a medication that helps control hunger and improves how your body uses insulin, making it easier for you to lose weight.

At MedExpress, we know every weight loss journey is unique. Starting treatment can feel like a daunting step, and it’s important to choose the right weight loss medication for you. Here, our experts break down what Mounjaro is, how it works and who can use it to help you make an informed decision about starting treatment.

Article Summary:

• Mounjaro is a brand name for tirzepatide, an injectable medication used for weight loss and type 2 diabetes.
• Tirzepatide is a dual GLP-1/GIP receptor agonist. It works by helping to control blood sugar levels and reduce appetite to support weight management.
• In clinical trials, people using the highest dose of Mounjaro lost an average of 22.5% of their body weight after 72 weeks (1 year, 5 months).

What is Mounjaro?

Mounjaro is the brand name for an injectable treatment containing tirzepatide. It was originally developed to treat type 2 diabetes, because it’s designed to lower and stabilise blood sugar and helps the body to release insulin when it’s needed. But it later emerged as a highly effective option for weight loss, delivering impressive results for many people.

Mounjaro isn’t a quick fix for weight loss. It must be used alongside lifestyle changes, including a reduced-calorie diet and increased physical activity, to achieve lasting weight management.

How does Mounjaro work?

Mounjaro contains the active ingredient tirzepatide, which mimics two naturally occurring hormones in your gut: glucagon-like peptide-1 (GLP-1) and gastric inhibitory polypeptide (GIP). These hormones help control blood sugar levels and signal to your brain to reduce appetite, helping to reduce food cravings. They also slow down the rate at which food leaves your stomach, helping you feel fuller for longer.

This also helps to reduce “food noise”, an informal term which describes the feeling of constant food-focused thoughts, such as what to eat, when to eat, and how much to eat.

Because Mounjaro mimics two hormones instead of one, it’s more effective for weight loss than other injectable medications. Studies show that, by reducing your food intake and slowing down digestion, Mounjaro can lead to a significant decrease in calorie consumption.

If you’re eligible for a prescription, you take it once a week with a pre-filled pen, self-injecting into your abdomen, thigh, or upper arm. The Mounjaro pen is designed to be minimally invasive, with small needles for comfort. However, you should rotate injection sites weekly with each dose to prevent irritation, bruising, or lumps under the skin.

Mounjaro in the UK

You can support your weight loss with Mounjaro in the UK. It’s approved by the MHRA (Medicines and Healthcare products Regulatory Agency) and by the National Institute for Health and Care Excellence (NICE) for the treatment of obesity and weight management. It’s backed by strong clinical evidence from trials.

Mounjaro is only available on prescription, and should be used under specialist medical supervision. MedExpress offers support throughout your treatment, so you can get expert guidance whenever you need it.

How effective is Mounjaro?

In clinical trials, people using Mounjaro experienced significant weight loss. On average, those on the highest dose of 15mg lost 22.5% of their body weight on average after 72 weeks (1 year, 5 months). [1]

Mounjaro has also been shown to have additional health benefits. Studies show tirzepatide can help to reduce waist size, lower blood pressure, and decrease 'bad' cholesterol levels. [1]

By helping you to lose weight, Mounjaro can have a positive and protective impact on your overall health, particularly in relation to your heart. In one study it was found that it improves blood pressure, lipids, and markers of inflammation and arterial stiffness, and can help lower the risk of cardiovascular disease. [2]

Read more about what results users are experiencing on Mounjaro here, and how it compares to other treatments like Wegovy.

Mounjaro side effects

Like all medications, Mounjaro can cause some side effects. You must be aware of them before starting treatment. These are the common side effects of tirzepatide:

• Nausea, diarrhoea, or vomiting are very common, but will settle with time.
• You may also have constipation, indigestion, and abdominal pain. Our clinical team can offer support to help you relieve these symptoms.
• Injection site reactions can cause redness and irritation. These are generally mild.

Comparison of very common side effects in clinical trials

*The percentages indicate the proportion of trial participants who experienced each side effect.

You can help manage side effects with dietary changes, like choosing bland foods and staying hydrated. We also recommend that you limit caffeine and alcohol intake, stay active and speak to our clinical team for advice on changing dosage or timing to relieve symptoms.

Following the prescribed dosage

Mounjaro starts at a low dose (2.5mg) and may be increased gradually if needed, until you reach the maximum dose or a dose that works for you. Our clinicians review your progress regularly and will only adjust your dose if it’s safe, appropriate, and helping you make steady progress. We’ll keep you informed every step of the way with reminders and guidance designed to make treatment simple and supportive.

Reminder: The right dose for you is one where you’re seeing steady weight loss (around 0.5–1kg per week) and you feel like you can stick with it. If you’re not quite there yet, or things feel too fast, it’s okay to take more time at a lower dose. This is about finding what works for you.

Our clinical team will check in on your progress throughout your journey. To continue prescribing Mounjaro, we review how treatment is working for you. As a guide, this usually means seeing at least a 5% reduction in your starting body weight after 6 months, which helps us ensure the medication is providing a meaningful benefit for your health.

Who can use Mounjaro?

It’s important to know if you can safely use Mounjaro and make the lifestyle changes that come with taking it. For best results, Mounjaro should be paired with a lower-calorie diet and more physical activity.

Whether it’s right for you will depend on your medical history and your current health. You’re eligible to take Mounjaro if you are an adult over the age of 18, and have a body mass index (BMI) of 30 and above. You may be also eligible if you have a BMI of 27 and above along with a weight-related health condition. These related concerns include high blood pressure, type 2 diabetes, heart disease and high cholesterol.

Mounjaro isn’t suitable for you if you have:

• Severe kidney or liver problems
• Type 1 diabetes
• A personal or family history of thyroid cancers or certain genetic conditions
• An allergy to tirzepatide or any other ingredients in Mounjaro

Mounjaro is not suitable if you’re pregnant or breastfeeding. It may also make oral birth control less effective by lowering hormone levels in your blood. We recommend adding an additional barrier method of contraception if you are a woman of childbearing age, such as condoms, or switching to a non-oral method like an IUD to stay protected.

If you have a history of pancreatitis, serious digestive issues, diabetic retinopathy or kidney problems, speak to your GP or healthcare provider before starting Mounjaro.

Ready to start your weight loss journey?

Find out what treatment is suitable for you by completing a short online consultation on our website.

References:

1. Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, et al. Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine [Internet]. 2022 Jun 4;387(3):205–16. Available from: https://www.nejm.org/doi/full/10.1056/NEJMoa2206038
2. O’Riordan M. SURPASS-CVOT Published: Large Trial Confirms CVD Efficacy of Tirzepatide [Internet]. TCTMD.com. 2025 [cited 2026 Feb 23]. Available from: https://www.tctmd.com/news/surpass-cvot-published-large-trial-confirms-cvd-efficacy-tirzepatide
3. Frías JP, Davies MJ, Rosenstock J, Pérez Manghi FC, Fernández Landó L, Bergman BK, et al. Tirzepatide versus Semaglutide Once Weekly in Patients with Type 2 Diabetes. New England Journal of Medicine [Internet]. 2021 Jun 25;385(6):503–15. Available from: https://www.nejm.org/doi/full/10.1056/NEJMoa2107519