Slimming Injections: What They Are and How to Track Your Journey

Slimming injections such as Wegovy and Mounjaro are once-weekly injectable medicines prescribed for weight management in adults who meet clinical criteria. Wegovy contains semaglutide, a GLP-1 receptor agonist, while Mounjaro contains tirzepatide, which acts on both GLP-1 and GIP receptors. Both work by influencing appetite-regulating pathways — many people report reduced hunger, lower "food noise", and a greater sense of fullness after eating. According to NHS guidance, these medicines are used alongside diet and lifestyle changes, not as a standalone solution.

Are they safe?

Both medicines are prescription-only for good reason: suitability is assessed individually by a prescriber who considers your full medical history. They are not suitable for everyone, and like all medicines they carry the possibility of side effects — gastrointestinal symptoms such as nausea, constipation, and indigestion are among the most commonly reported. They both carry a black triangle (▼) status in some countries, meaning any suspected side effects should be reported to your national reporting scheme (such as the UK's Yellow Card scheme) as well as to your healthcare professional. If you have questions about whether these injections are right for you, or about any symptoms you experience, speak with your prescriber or doctor.

Injection sites and rotation

These medicines are injected under the skin (subcutaneously), typically into the abdomen, upper thigh, or upper arm. Rotating the injection site each week is generally recommended to help avoid skin irritation or changes at any one spot. The specific sites suitable for you and the technique involved are covered in the patient information leaflet that comes with your pen — and your prescriber or pharmacist can walk you through it. For a broader look at how these medicines work at a biological level, see our guide on how slimming injections work. You may also find useful background in our overview of slimming injections generally.

Remembering which site you injected last week — and keeping a reliable record of every dose — is harder than it sounds when you are managing a weekly schedule alongside everything else in life. GLP Trackr's injection-site tracking and rotation feature is built specifically for this: log each injection with the site you used (abdomen, thigh, or arm), and the app keeps a running rotation history so you always know where to inject next.

Beyond site rotation, the app also logs your dose strength and the date and time of each injection, giving you a clear, timestamped record you can refer back to. Dose reminders mean a weekly shot is much less likely to be forgotten — particularly useful during the early weeks when the routine is still new. You can also log any side effects you notice after each injection, building a picture over time that is genuinely useful to bring to your next prescriber appointment.

For a deeper look at the wider injection journey — including what to expect at different stages — visit our weight loss injections hub. If you are specifically on semaglutide, our page on semaglutide weight loss injections covers what many people experience on that medicine. You can also read more about tracking slimming injections and what others commonly report in our slimming injections experience guide.

GLP Trackr is free to try for 7 days — download it on the App Store or Google Play and let the app handle the rotation tracking so you can focus on the journey itself.

A note on safety: GLP Trackr is a tracking and journaling app, not a medical service. If you experience symptoms that feel severe, persistent, or worrying — at any point in your treatment — contact your healthcare professional promptly. Any decisions about your injection schedule or dose belong with your prescriber, not an app.