Mounjaro Injection Doses: Understanding Your Starting and Titration Strengths

Mounjaro is a once-weekly injectable medicine whose active substance, tirzepatide, acts on both GLP-1 and GIP receptors — pathways involved in appetite regulation and blood sugar management. It is supplied as pre-filled pens across a range of strengths: commonly 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, and 15 mg.

Starting low and titrating up

A low starting dose — typically 2.5 mg — is standard practice. Beginning at the lowest strength allows the body to adjust gradually, which many people find helps with the gastrointestinal side effects that are commonly reported in the early weeks. From there, dose increases are made by the prescriber at intervals they determine, based on how well the medicine is being tolerated and the individual's response.

It is worth being clear: no page, app, or online resource can tell you when your dose should change. That decision belongs with your prescriber or doctor, who knows your full medical history.

What the pen strengths mean in practice

Each pre-filled pen delivers a single fixed dose. The 2.5 mg and 5 mg pens are most associated with the early stages of treatment; strengths such as 7.5 mg and above tend to come later in the titration schedule. Your prescriber will specify which pen to use at each stage. For the most accurate and up-to-date product information, the electronic Medicines Compendium (eMC) holds the full summary of product characteristics for Mounjaro.

If you would like a broader overview of how Mounjaro injections work in general, the guide to Mounjaro injections covers the essentials. For a deeper look at how doses are structured across the full titration schedule, see Mounjaro injection doses explained. You can also read more in our overview of weight-loss injections.

Keeping track of which dose strength you are on, when you last injected, and which site you used is where GLP Trackr is most useful — especially when your pen strength changes at a titration step.

The app's injection-site tracking and rotation feature lets you log the site of each injection (abdomen, thigh, or upper arm) and automatically suggests your next rotation site, so you are never guessing where to inject next. Alongside this, the dose logging feature lets you record the exact strength of each pen used — so if you move from 2.5 mg to 5 mg, or from 5 mg to 7.5 mg, that change is captured clearly in your history. Weekly dose reminders mean a busy week is far less likely to result in a missed injection.

Having a clear, timestamped log of every dose and strength you have taken is also genuinely useful when you see your prescriber — you can show them exactly what you have been taking and when, without relying on memory. The Mounjaro pen and injection guide has more on what to note at each injection.

Any decision about your current dose strength or when to move to the next step should always be made with your prescriber — never on your own. If you have questions about which pen strength is right for you, or whether it is time to adjust, contact your healthcare professional directly.

Ready to keep your Mounjaro schedule organised in one place? Download GLP Trackr free on the App Store or Google Play and start a 7-day free trial — log your dose strength, rotation history, and weekly reminders from day one.