Mounjaro Instructions: Key Things to Know When You're Already Prescribed

Mounjaro (tirzepatide) and Wegovy (semaglutide) are both once-weekly injectable medicines supplied as pre-filled pens. While the specific steps for each device are detailed in the leaflet inside your pack — and on the electronic Medicines Compendium at medicines.org.uk — the broad principles people on GLP-1 treatment commonly follow include:

• Check your pen before use. Inspect the solution through the viewing window; it should be clear and colourless to slightly yellow. Check the expiry date on the label. If anything looks unusual, contact your pharmacist or prescriber before injecting.
• Let it come to room temperature. Most people find the injection more comfortable when the pen has been out of the refrigerator for a short while. Check your patient leaflet for the exact guidance — it will specify how long the pen can safely be kept at room temperature.
• Choose an injection site. Common sites are the abdomen (stomach area), front of the thigh, or upper arm. Each site has different absorption characteristics; your prescriber or the leaflet will guide you on what is appropriate for you.
• Rotate your sites. Injecting into the same spot repeatedly can cause skin changes over time. Rotating between and within sites — for example, different areas of the abdomen — is widely recommended. Your patient information leaflet will give specific guidance.
• Do not reuse needles. Each injection requires a new, sterile needle.
• Dispose of used pens and needles safely. Use a sharps container; guidance on disposal varies by country, so check local arrangements or ask your pharmacy.

For pen-specific step-by-step instructions for Wegovy, see our guide on using the Wegovy pen. If you want to hear how others on Mounjaro approach their weekly routine, the Mounjaro community forums can be a useful source of real-world experience.

Always treat the leaflet that came with your specific pen as the definitive source — instructions can vary between pen strengths and device generations, and the information here is general rather than device-specific.

One of the easiest things to lose track of on a weekly injection schedule is which site you last used — especially when you are rotating across multiple areas. GLP Trackr's injection-site tracking logs every injection with its location and date, then suggests your next rotation site automatically, so you never have to remember on your own.

Alongside site tracking, the app's dose logging lets you record each injection — date, time, and dose strength — in one place. This running log is especially useful to bring to prescriber appointments, giving your healthcare professional a clear picture of your schedule rather than relying on memory. If you ever have a question about your routine, having a documented history makes those conversations more productive.

For a full overview of managing your Mounjaro treatment, visit our Mounjaro information hub.

A note on side effects and safety: If you experience anything unexpected after an injection — including severe or persistent pain at the injection site, signs of an allergic reaction, or any symptom that concerns you — contact your healthcare professional promptly. Do not attempt to adjust your dose or technique based on general guidance alone; your prescriber knows your full medical history and is best placed to advise. Any side effects worth noting can also be reported to your national pharmacovigilance scheme (such as the UK's Yellow Card scheme) as well as to your healthcare team.

Ready to keep your weekly injection routine organised? GLP Trackr tracks your injection sites, logs every dose, and helps you spot patterns over time — available free on the App Store and Google Play, with a 7-day trial to get started.