Are Weight Loss Jabs Safe?

Mounjaro and Wegovy are both prescription-only medicines that have undergone clinical evaluation before receiving regulatory authorisation. That process includes assessment of their safety profile alongside their benefits. Both medicines carry a black triangle designation (▼) in the UK, meaning they are subject to additional monitoring so that new safety information can be identified quickly. Any suspected side effects should be reported to a healthcare professional and to your national pharmacovigilance scheme — for example, the UK Yellow Card scheme or the equivalent scheme in your country.

Commonly reported side effects

The most frequently reported side effects for both medicines are gastrointestinal: nausea, vomiting, diarrhoea, constipation, indigestion, and reflux. These are related to how the medicines affect appetite-regulating pathways and the speed at which the stomach empties. For many people these effects are most noticeable in the first days after a dose change and ease over time. Other commonly reported effects include fatigue, headache, dizziness, and reactions at the injection site.

When to contact a healthcare professional promptly

Some symptoms warrant prompt medical attention. These include severe or persistent abdominal pain (which could indicate a pancreas or gallbladder issue), a rapid or severe allergic reaction, significant changes in vision, or any symptom that is worrying you. Never wait to seek advice if something feels serious — contact your healthcare professional straight away. If you want a broader overview of how these medicines work and what to expect, the guide to weight loss injections covers the topic in more depth.

Who these medicines are not suitable for

Suitability depends on individual health factors including other medical conditions, other medicines being taken, and personal and family history. Your prescriber will have considered these before prescribing. These medicines are not suitable for everyone, and that assessment belongs with a qualified clinician — not with a tracking app or general information. If your circumstances have changed since you were prescribed, speak with your prescriber or doctor. You can also read more about what weight loss jabs are and Mounjaro as a weight loss injection for factual background on these specific medicines.

One of the most useful things you can do while taking a weekly injection is keep a clear, consistent record — both for your own awareness and to support productive conversations with your prescriber. GLP Trackr's injection-site tracking logs where each shot was given and automatically suggests your next rotation site, so you are not guessing or repeating sites more often than you should. Rotating sites correctly is important for skin health and consistent absorption, and having a reliable log removes the mental effort of remembering.

Alongside site rotation, the app's side-effect tracker lets you log how you feel each day — nausea, fatigue, injection-site reactions, or anything else — and surfaces patterns over time. If a symptom keeps appearing at a particular point in your weekly cycle, that is exactly the kind of insight worth bringing to your next appointment. The app's doctor report feature can turn your logged data into a clear summary to share with your prescriber.

GLP Trackr does not provide medical advice and is not a substitute for your prescriber's guidance. If you have concerns about your safety on this medication, contact your healthcare professional — always follow their advice over anything you read here. For information on how and where these injections are typically accessed, see the overview of weight loss jab pharmacies and NHS access.

Start logging your injections and tracking how you feel — GLP Trackr is free to try for 7 days on the App Store and Google Play.