Does the Slimming Injection Work?

Mounjaro and Wegovy belong to a class of medicines that act on appetite-regulating pathways in the brain. Wegovy contains semaglutide, a GLP-1 receptor agonist. Mounjaro contains tirzepatide, which acts on both GLP-1 and GIP receptors — making it a dual agonist. Both are given as once-weekly injections using a pre-filled pen.

In practical terms, many people prescribed these medicines describe a reduced sense of hunger and less preoccupation with food — sometimes called reduced "food noise". Stomach emptying can also slow, which contributes to a feeling of fullness after smaller meals. These effects are commonly reported, though not universal; individual responses vary.

It is worth being clear about what the injection is not: it is not a cosmetic quick fix, it does not replace a balanced diet and physical activity, and it is not suitable for everyone. Suitability is always decided by a prescriber based on your individual health picture.

Injection sites and how you take it

Both medicines are injected under the skin, typically into the abdomen, thigh, or upper arm. Rotating between sites with each weekly dose is generally recommended to allow the skin and tissue in each area to recover. Your prescriber or the patient information leaflet that comes with your pen will guide you on technique and any preferences specific to your prescription.

For more background on how these medicines are used, see our overview of weight-loss injections or explore what to expect when starting a slimming injection.

One of the most useful things you can do while on a weekly injection is keep a consistent record of what is changing — not just on the scale, but in your energy, appetite, and how you feel day to day. Progress on these medicines is rarely linear, and without a log it can be hard to see the pattern.

GLP Trackr is built specifically for people already prescribed Mounjaro or Wegovy. The app's injection-site tracking and rotation feature lets you log each dose, the site used, and the date — so you always know where you injected last and where to go next. Over time, that log becomes a clear record of your consistency, which is one of the biggest factors in getting results.

Alongside site tracking, the daily check-in captures weight, mood, energy, and appetite (including food noise) in about 30 seconds each morning. The insights feature then surfaces patterns in your own data — helping you spot what is and is not shifting, and giving you something concrete to bring to your next prescriber appointment.

If you have questions about accessing a prescription or what the process involves, the page on how to get the slimming injection covers the general pathway. For context on costs, see what the slimming injection costs — though any specific pricing should always come from your own pharmacy or prescriber.

Any decision about whether the injection is working well enough for you, or whether your dose or treatment needs reviewing, belongs with your prescriber or doctor. GLP Trackr helps you record the full picture so that conversation is as informed as possible — it is not a substitute for their clinical judgement. If you experience severe or persistent side effects at any point, contact your healthcare professional promptly.

Ready to start building that record? Download GLP Trackr on the App Store or Google Play and try it free for 7 days — log your first injection site today.