Mounjaro supports weight loss by mimicking two natural hormones in your body that help manage appetite and blood sugar levels. "By doing so, it helps you feel fuller for longer, which makes it easier to manage portion sizes, and stick to a healthy diet. By reducing cravings and promoting feelings of fullness, it helps you make more balanced food choices and gradually break away from unhealthy eating habits. When combined with balanced eating and regular exercise, Mounjaro can help people lose weight more effectively and maintain their results over time," says head pharmacist Jason Murphy.
The science behind how Mounjaro works explained simply
The main ingredient of Mounjaro is called tirzepatide, and unlike many other weight loss injections is known as a “dual agonist” treatment. "This is because it works on two natural hormones in the body called GLP-1 (glucagon-like peptide-1) and GIP (glucose-dependent insulinotropic polypeptide), whereas many other injections mimic only the GLP-1 hormone," says Jason.
"By copying these hormones, Mounjaro sends signals to your brain that you’re full or as if you’ve just eaten, helping to reduce your appetite alongside delaying how quickly your stomach empties in order to make you feel fuller for longer."
© UCG/Universal Images Group via GA clear guide on what to expect
Mounjaro comes in a KwikPen, a pre-filled, disposable pen designed for single-patient use. Each pen contains four doses, which are taken once a week, so one pen lasts about a month. "It is used to help manage type 2 diabetes and obesity, alongside a healthy diet and regular exercise. When you use Mounjaro, you may notice reduced hunger and fewer cravings almost straight away. Over time, this can lead to noticeable weight loss, with clinical studies showing people lose more weight than with diet and exercise alone," says Jason.
"As with any prescribed medication, some people can also experience side effects such as nausea, diarrhoea and constipation. However, these can easily be managed safely at home with small diet and lifestyle changes such staying hydrated, eating a balanced diet containing plenty of fibre, whole foods and protein and moving more," he adds.
© Getty ImagesDr Angela Kwong adds: "While some may experience reduced food noise and lowered appetite early on, it's important to know that the lower doses are there to help acclimatise your body to the medication and it's important to not rush with increasing the dose or expect full suppression early on.
"In the meantime, implementing lifestyle changes are important - ensuring good sleep habits, a regular exercise regimen and optimised eating habits to set you up for success."
How long does it take for Mounjaro to work?
Most people notice a difference in their hunger and food cravings almost straight away, often within the first few weeks of treatment. "On the highest maintenance dose of 15mg, clinical studies show people lost up to 22.5% of their starting weight over 72 weeks," says Jason.
"Mounjaro has been clinically proven to help people lose weight faster than diet and exercise alone, but consistency is key. Sticking with the treatment, alongside a balanced diet and regular exercise, will help you achieve the best results."
© Getty ImagesDr Angela Kwong asserts it can vary from person to person, however. "Some may experience reduced appetite and food noise early on during the acclimatisation phase. For others, this happens later at the treatment doses. As it can vary widely, it's important to have regular check-ups with your prescriber to ensure that you're taking the right dose for you," she says.
Is Mounjaro safe?
It’s normal to have concerns when starting a new medication but Mounjaro is safe for most people when taken as prescribed under the guidance of a clinician.
"It has been approved by multiple UK regulatory agencies, including the MHRA, NICE, and the NHS, and has undergone extensive clinical trials. Most side effects are mild and usually resolve on their own within four to eight weeks, while serious side effects are extremely rare," says Jason.
© Getty ImagesExpert bios
- Dr. Angela Kwong, MBBS DCH FRACGP is a Sydney-based GP and the NSW State Lead for the RACGP Specific Interests Group in Obesity Management. She is the Founder of Enlighten Me, an award-winning medically supervised weight management program and doctor designed meal replacement shake.
- Jason Murphy is the Head Pharmacist of Chemist4U. He graduated from Queen's University Belfast in 2007 and became a dedicated member of the Pharmaceutical Society of Northern Ireland. He focuses on weight management, combining clinical expertise with a passion for accessible healthcare.
