How Does Mounjaro Work? The Detailed Guide

It is estimated that 1 in 4 adults in the UK currently live with obesity. Obesity is a complex chronic disease that progressively worsens. This health condition is also a risk factor for developing other severe health conditions such as type 2 diabetes, some types of cancer, high blood pressure, and coronary heart disease.

When weight loss efforts are not working, treatments such as Mounjaro can be used with lifestyle changes to aid weight loss. In this article, we discuss precisely how Mounjaro works.

What is Mounjaro?

Mounjaro is an injectable medicine containing the active ingredient tirzepatide. It is a prescription medicine that is licensed for the treatment of obesity and type 2 diabetes.

Mounjaro works by targeting two hormones: glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP).

GLP-1 is a hormone released from your digestive tract when you eat. It promotes the feeling of fullness. GIP stimulates the release of insulin, helping control blood sugar levels. Mounjaro also slows down how fast food empties from the stomach.

This medication is prescribed in combination with a reduced-calorie diet and exercise.

How does Mounjaro work?

The active ingredient of Mounjaro is tirzepatide. It is a synthetic dual agonist for the GIP receptor and GLP-1 receptor. Tirzepatide is a 39-amino-acid-modified peptide with a C20 fatty diacid moiety that allows albumin binding as well as a prolonged half-life.

Tirzepatide binds to and activates the GIP and GLP-1 receptors, which are the targets for the naturally occurring hormones GIP and GLP-1. Tirzepatide improves first- and second-phase insulin secretion and lowers glucagon levels.

In patients with type 2 diabetes, tirzepatide lowers the fasting and postprandial glucose concentration, lowers body weight, and decreases food consumption.

Glucagon secretion

Glucagon is a hormone secreted by the pancreatic alpha cells. It stops blood sugar from dropping too low.

Tirzepatide reduces fasting and postprandial (after a meal) glucagon concentration. In studies, tirzepatide 15mg lowered fasting glucagon concentration by 28% and lowered glucagon AUC after a meal by 43%.

Gastric emptying

Gastric emptying is the rate at which the stomach empties. Tirzepatide slows food and liquids from emptying the stomach, leaving users feeling fuller. It also slows post-meal glucose absorption, lowering after-meal glucose.

Insulin sensitivity

Insulin sensitivity, also known as insulin resistance, leads to increased blood sugar levels. Insulin plays an important role in controlling the amount of glucose (sugar) in the blood. If left untreated, insulin resistance can lead to type 2 diabetes. Tirzepatide improves insulin sensitivity, helping manage blood sugar levels.

Conditions treated by Mounjaro

Mounjaro is licensed for the treatment of type 2 diabetes and weight loss. Here’s how Mounjaro works to treat these conditions.

How does Mounjaro work for type 2 diabetes?

Mounjaro is prescribed for adults over 18 years with type 2 diabetes. This medication can be prescribed to adults with type 2 diabetes when:

• Diabetes medications have not been effective in managing diabetes.
• The patient is unable to take other diabetes medications due to other medical conditions or side effects.

Mounjaro is only used for those with type 2 diabetes who have a Body Mass Index (BMI) of 35kg/m2 and with other conditions related to obesity. However, some patients can be prescribed Mounjaro if their BMI is below 35kg/m2 if:

• Using insulin increases the risk of developing hypoglycemia (low blood sugar)
• Weight loss leads to improvements in weight-related health conditions

The National Institute for Health and Care Excellence (NICE) recommends that patients from Black African, Asian, South Asian, Chinese, African-Caribbean, and Middle Eastern backgrounds receive Mounjaro treatment at a lower BMI. This is due to their risk of developing weight-related health conditions at a lower BMI.

How does Mounjaro work for weight loss?

In 2023, Mounjaro was approved for treating obesity and for overweight individuals. This medication can be prescribed with a reduced-calorie diet and increased exercise for those who:

• Have a BMI below 35kg/m2 with additional weight-related medical conditions such as prediabetes, high blood pressure, obstructive sleep apnea, history of heart disease and stroke, and type 2 diabetes.
• Have obesity (BMI of 30kg/m2 or greater).

How long does Mounjaro take to work?

When it comes to how quickly Mounjaro works, generally, it takes a couple of hours to start feeling the effects after the first injection. It then takes an additional 8-72 hours for this medication to reach peak levels in the body.

After injecting it into the skin, the average bioavailability of Mounjaro is 80%. Similar bioavailability of this medication was achieved when injecting it into the upper arm, stomach, or thigh.

Mounjaro comes in the following dose strengths:

• 2.5mg
• 5mg
• 7.5mg
• 10mg
• 12.5mg
• 15mg

The starting dose is 2.5mg, administered once weekly. After four weeks, the dose slowly increases to 5mg once a week. The maximum dose of Mounjaro is 15mg once weekly.

The half-life of the active ingredient tirzepatide is five days. It takes 30 days for Mounjaro to completely clear out the body after stopping it.

How long does it take for Mounjaro to kick in for weight loss?

In a 2022 study, patients using tirzepatide and a recommended diet and exercise started experiencing weight loss in the first weeks. Patients started on a dose of 2.5mg of Mounjaro injected once weekly. The dosages increased to either 5mg, 10mg, or 15 mg once weekly for the rest of the study.

Throughout the study (72 weeks), patients on 10mg of Mounjaro lost an average of 19.5% of their starting weight, while those on 15mg lost an average of 20.9% of their starting weight.

Benefits and side effects of Mounjaro

Benefits

Outside of weight loss and management, Mounjaro may offer other benefits such as:

• Lower blood sugar
• Reduced need for insulin or other diabetes medication
• Potential positive effects on cardiovascular disease such as lowering blood pressure and reducing the risk of major heart events

Side effects

Like any medication, there are side effects; however, not everyone may experience them.
Common side effects of Mounjaro (1 in 10 people):

• Hypoglycemia (low blood sugar)
• Nausea
• Constipation
• Diarrhoea
• Vomiting
• Dizziness
• Flatulence (gas)
• Heartburn or acid reflux
• Fatigue
• Increased pancreatic enzyme levels
• Fast pulse (common side effect when used for Type 2 diabetes patients)
• Allergic reaction (e.g., eczema, rash, itching)
• Decreased appetite
• Stomach pain
• Bloating
• Burping
• Indigestion

Uncommon side effects of Mounjaro (up to 1 in 100 people):

• Hypoglycemia (when used for patients with type 2 diabetes)
• Fast pulse (in weight loss management patients)
• Cholecystitis (gallbladder infection)
• Injection site pain
• Gallstones
• Increased calcitonin levels in the blood
• Weight loss in type 2 diabetes patients

Talk to your doctor or pharmacist if you experience persistent mild side effects that do not clear.
Uncommon serious side effects (up to 1 in 100 people):

• Acute pancreatitis (inflamed pancreas) can cause persistent and severe pain in the stomach and back

Rare serious side effects (up to 1 in 1000 people):

• Severe allergic reaction (e.g., angioedema, anaphylactic reaction)

If you experience any serious side effects, seek immediate medical attention or call 999. The Patient Information Leaflet contains a list of all of Mounjaro’s reported side effects.

Considering Mounjaro: Next steps for potential users

Mounjaro is a prescription injection to aid adults with type 2 diabetes and help treat those with obesity or who are overweight with weight-related health conditions.

In the UK, Mounjaro can only be purchased with a prescription from a healthcare professional at a registered pharmacy. One such pharmacy is Cloud Pharmacy. You can purchase Mounjaro KwikPens after completing a quick health questionnaire.

After a free online consultation with a registered pharmacist who will determine what weight loss treatment is best for you, the medication will be discreetly and securely delivered to your UK address. Cloud Pharmacy also provides all patients with confidential follow-ups and advice along their weight loss journeys.

Click here to book a consultation with Cloud Pharmacy.

FAQs

How does Mounjaro help you lose weight?

Mounjaro mimics or acts similarly to the hormones GIP and GLP-1, which are naturally produced in the intestinal tract. This results in the feeling of fullness, helping the user with hunger and portion control. Mounjaro also slows down digestion.

What does Mounjaro do to your hormones?

Mounjaro acts like two digestive hormones, glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). These naturally occurring digestive hormones play a role in digestion speed, blood sugar control, and appetite. GLP-1 lowers blood sugar, making you feel fuller for longer after you eat. The GIP hormone increases the release of insulin, which is required to turn sugar into energy.

What is the mechanism of action of Mounjaro for weight loss?

The active ingredient tirzepatide is a single molecule that activates (selectively binds to) GLP-1 receptors and GIP receptors in the body. GLP-1 and GIP are both naturally occurring incretin hormones. This results in the enhancement of insulin secretion, improvement of insulin sensitivity, and decreased food consumption.

Sources & method

• https://www.cloudpharmacy.co.uk/
• https://www.cloudpharmacy.co.uk/online-doctor/weight-loss-treatments/mounjaro-weight-loss-injection/
• https://www.diabetes.org.uk/guide-to-diabetes/managing-your-diabetes/treating-your-diabetes/tablets-and-medication/glp-1/mounjaro
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10231274/
• https://www.gov.uk/government/news/mhra-authorises-diabetes-drug-mounjaro-tirzepatide-for-weight-management-and-weight-loss
• https://mounjaro.lilly.com/hcp/how-mounjaro-works
• https://pi.lilly.com/us/mounjaro-uspi.pdf?s=pi
• https://www.medicines.org.uk/emc/files/pil.15481.pdf
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10159347/
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9268041/
• https://biomedres.us/pdfs/BJSTR.MS.ID.008226.pdf
• https://www.nhs.uk/conditions/obesity/
• https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/2821080
• https://jamanetwork.com/journals/jama/fullarticle/2812936
• https://www.nature.com/articles/s41591-023-02597-w
• https://mounjaro.lilly.com/hcp/a1c-weight