Which Diabetes Injection Is Used for Weight Loss?

Semaglutide (the active substance in Wegovy) and tirzepatide (the active substance in Mounjaro) are both prescription-only, once-weekly injectable medicines. They were each developed in the field of metabolic medicine and are now prescribed for weight management in eligible adults, subject to a prescriber's assessment.

How they work

Semaglutide acts on GLP-1 receptors — pathways involved in appetite regulation, feelings of fullness, and the rate at which the stomach empties. Tirzepatide acts on both GLP-1 and GIP receptors, making it a dual-action medicine. Many people on either medicine report a noticeable reduction in appetite and what is often called "food noise" — the persistent preoccupation with eating. These are commonly reported effects, not guarantees; individual experience varies.

How they are given

Both medicines come as pre-filled injection pens and are administered once a week, typically into the abdomen, thigh, or upper arm. Rotating the injection site — moving around the body rather than reusing the same spot — is a standard part of managing these injections. Your prescriber or the patient information leaflet that came with your pen will guide you on technique.

For a broader overview of how injectable weight-loss medicines work and what to expect, see our guide to weight-loss injections. You may also find it useful to read about the diabetic injection used for weight loss or our page covering the diabetes injection prescribed for weight loss in more detail.

Suitability is decided by your prescriber

Neither medicine is suitable for everyone. Your prescriber will have assessed your individual health history, other medicines you take, and any contraindications before prescribing. If you have questions about whether the medicine is right for you, or about how to take it, that conversation belongs with your healthcare professional — not a tracking app.

Once you are prescribed a once-weekly injection, keeping a clear record of each dose is more useful than it might sound. Weeks blur together, injection sites are easy to repeat by habit, and a missed or delayed dose can be hard to reconstruct from memory alone.

GLP Trackr's injection-site tracking and rotation feature is built for exactly this. Each time you inject, you log the site — abdomen, thigh, or upper arm — and the app records your rotation history, then suggests where to inject next. Over time, you build a clear picture of your injection pattern without having to remember it yourself. You can also log the dose strength and date of every injection, so your full treatment history is always in one place.

If you ever miss a dose and want to note it before speaking to your prescriber, the app lets you log that too — giving you something concrete to discuss at your next appointment rather than trying to recall from memory. Any decision about what to do after a missed dose belongs with your prescriber or doctor, not the app.

Our guide to injections for weight loss covers more on what to expect throughout your treatment.

If you ever notice anything at an injection site — redness, swelling, or unusual discomfort — or have any concerns about your medicine, contact your healthcare professional promptly. Side effects and reactions should also be reported to your national reporting scheme (such as the UK's Yellow Card scheme or your country's equivalent).

Ready to take control of your injection routine? GLP Trackr is free to try for 7 days — download it on the App Store or Google Play and let the rotation tracker do the remembering for you.