Weight Loss Medication FAQs

Mounjaro is a prescription-only weight-loss treatment. It uses the active ingredient tirzepatide; a long-acting glucose-dependent insulinotropic polypeptide (GIP) receptor and GLP-1 (glucagon-like peptide-1) receptor agonist, to increase the body’s secretion of and sensitivity to insulin.

Mounjaro was authorised for use by type-2 diabetes patients and overweight patients in the UK by the Medicines and Health Regulatory Agency (MHRA) in November 2023.

Mounjaro is a prescription weight loss medication that works by mimicking the actions of two naturally occurring hormones, GLP-1 and GIP. These hormones play key roles in regulating appetite, blood sugar levels, and digestion. By mimicking these hormones, Mounjaro leads to patients feeling full sooner after eating, and having less cravings for food. Additionally, it slows down the emptying of the stomach, making you feel fuller for longer and reducing your overall food intake.

Mounjaro is a prescription-only treatment. It can be used by eligible patients with a BMI of 30kg/m2 or more, or for those with a BMI of 27-30kg/m2, meaning respectively those who fall into the BMI categories of ‘obese’ and ‘overweight’. It is also used in patients with type-2 diabetes.

Mounjaro is administered in a pre-filled injection pen once a week. Patients using Mounjaro will start with a dose of 2.5mg, increasing to 5mg after four weeks. Further increases in dose might be recommended by a healthcare professional depending on the response to the treatment.

The maximum dose of Mounjaro is 15mg once weekly.

If you forget an injection of Mounjaro, you can take it up to four days, or 96 hours late. If you have missed this window, wait to take your next injection at the original scheduled time, and be cautious not to take two injections.

Mounjaro should be injected under the skin of the stomach, thigh, or upper arm. If you choose to administer Mounjaro via the stomach or thigh you can administer by yourself, while administration via the upper arm will require help.

Mounjaro and similar weight loss treatments are designed to be used in conjunction with a healthy diet and exercise plan. Exercise and a healthy diet are an essential part of any weight loss journey and will help to enforce habits that ensure the results achieved through your course of Mounjaro are lasting.

It isn’t known how Mounjaro interacts with alcohol use, however, your GP might advise you against drinking or to limit your consumption of alcohol. Alcohol has an impact on blood sugar levels, which Mounjaro aims to manage. As such, alcohol might limit the drug's capacity to work effectively.

However, since a healthy diet is recommended in conjunction with the use of Mounjaro, limiting your alcohol consumption when using the weight medication can support your weight loss journey. Alcohol is high in calories, can encourage unhealthy eating habits and amplify cravings for greasy and high-fat foods. By reducing alcohol consumption while using Mounjaro, patients are more likely to get the best results from the drug.

Mounjaro side effects

Like all medications, Mounjaro has been seen to cause some side effects. It is not a guarantee that you will experience any side effects while using the drug, but it is wise to familiarise yourself with the common side effects users might experience.

The most common side effects of Mounjaro are:

• Diarrhoea
• Feeling sick (nausea)

The most common side effects of Mounjaro are usually mild and will typically subside within a few weeks. These side effects are often the body's initial response to the introduction of an unfamiliar chemical and to mitigate these effects, Mounjaro is introduced gradually to give your body time to adjust to the treatment.

Common side effects of Mounjaro include:

• Fast pulse
• Mild to moderate allergic reaction, such as eczema, itching, or a rash
• Decrease in appetite
• Stomach pain
• Vomiting
• Constipation
• Indigestion
• Bloating
• Gas and burping
• Heartburn or reflux
• Fatigue
• An increase in the levels of pancreatic enzymes, which will show up on a blood test
• Itching, redness, or irritation at the injection site

Uncommon side effects of Mounjaro include:

• Gallstones
• An increase in calcitonin (a hormone that helps to control calcium levels)

In very rare cases, Mounjaro can cause a serious allergic reaction. This is known as anaphylaxis and causes breathing difficulties, throat, face and mouth swelling, and fainting.

Another rare side effect it can cause is an inflamed pancreas, known as acute pancreatitis. These side effects require urgent medical attention, so speak to your doctor or call 111 or 999 if you have intense and persistent stomach and back pain during treatment.

Always read the patient information leaflet for any treatment you are using or considering using.

As of 2024, Mounjaro can be prescribed through the NHS for those living with type-2 diabetes or obesity. Must have a BMI >40 and living with diabetes, hypertension, CVD, or sleep apnoea. For people from black, Asia or ethnic minority back ground BMI is reduced to 37.5.