How to Start Mounjaro: What to Know Before Your First Dose

Mounjaro (tirzepatide) is a once-weekly injectable medicine. Your prescriber will have set your starting dose and given you instructions specific to your situation — those instructions are the ones that matter most. The general pattern described in the prescribing information is to begin at a low dose and adjust over time, but any change to your dose is always your prescriber's decision, not something to navigate alone.

Choosing the best day to start

One of the first practical decisions is which day of the week to inject. There is no universally 'best' day to start Mounjaro — what matters most is picking a day you can reliably stick to each week. Many people choose a day when they are at home or have a lighter schedule, particularly for their first few doses, so that if they experience any nausea or fatigue they can rest if needed. Once you have chosen a day, try to stay consistent — the same day each week helps keep the medicine working as intended.

What commonly happens in the first few weeks

In the early weeks, it is common to notice changes in appetite, and some people experience gastrointestinal side effects such as nausea, indigestion, or feeling full quickly. These effects are widely reported and often settle as the body adjusts. Keeping a simple record of how you feel after each dose can be genuinely useful — patterns that seem random in the moment often become clearer when you look back over several weeks.

If you want to understand more about how the medicine works in your system, our guide to when Mounjaro reaches peak activity explains the timing involved. For a broader overview of the medicine, the Mounjaro information hub covers the key topics in one place.

If you feel nervous about starting

Feeling scared to start is more common than you might think. Concerns about injecting, side effects, or whether it will work for you are all understandable. The most helpful thing you can do is go into your first dose prepared: read the patient information leaflet that came with your pen, follow your prescriber's guidance, and have a way to note down any symptoms so you can discuss them at your next appointment. You are not expected to have everything figured out on day one.

The single most valuable thing you can do when starting Mounjaro is stay consistent — with your injection day, your observations, and your conversations with your prescriber. GLP Trackr is built to make that consistency easy.

The dose and injection logging feature lets you record each shot the moment you take it — date, dose strength, and injection site — so you always have a clear record of where you are in your schedule. Set up a weekly reminder and you are far less likely to lose track of your injection day, especially in the early weeks when the routine is still new. You can also explore our guide to getting started with your Mounjaro routine for practical day-one tips.

Alongside dose logging, the side-effect tracker lets you note how you feel after each injection — nausea, energy levels, mood, sleep — and see those notes as a timeline. When you next speak to your prescriber, you will have something concrete to share rather than trying to recall how you felt three weeks ago.

GLP Trackr is free to try for seven days and available on the App Store and Google Play. Start logging from your very first dose and give yourself a head start on understanding your own journey.

GLP Trackr provides tracking and general information only — it is not a substitute for the advice of your prescriber or doctor. If you have any concerns about starting Mounjaro, how you feel after your first doses, or anything that worries you about your treatment, speak to your healthcare professional promptly. They know your full medical history and are best placed to guide you.