What Are the Ingredients in Mounjaro — and How Do They Work?

The single most important component in any medicine is its active ingredient — the substance that produces the pharmacological effect. Everything else in the formulation is there to keep that active ingredient stable, adjust the pH, or aid delivery.

Mounjaro (tirzepatide)

The active ingredient in Mounjaro is tirzepatide. Tirzepatide is a synthetic peptide that acts on both glucose-dependent insulinotropic polypeptide (GIP) receptors and glucagon-like peptide-1 (GLP-1) receptors — which is why it is described as a dual agonist. This dual action influences appetite-regulating pathways and slows gastric emptying, effects that are commonly reported by people taking the medicine.

The inactive ingredients (excipients) in Mounjaro's solution typically include substances such as sodium phosphate dibasic heptahydrate, sodium phosphate monobasic monohydrate, mannitol, polysorbate 80, and water for injection — though the precise list can vary by strength and presentation. Always check the patient information leaflet that came with your pen, or consult the full product details on the electronic Medicines Compendium (eMC), for the authoritative and up-to-date excipient list specific to your device.

If you have a known allergy or sensitivity to any component, speak with your prescriber or doctor before using the medicine.

Wegovy (semaglutide)

The active ingredient in Wegovy is semaglutide, a GLP-1 receptor agonist. Like tirzepatide, it acts on appetite-regulating pathways and is associated with a reduction in food noise — the persistent background preoccupation with food that many people on these medicines report diminishing. Wegovy's inactive ingredients similarly include stabilisers, pH adjusters, and water for injection; again, the patient information leaflet is the definitive source for your specific pen.

What these ingredients are not

Neither Mounjaro nor Wegovy contains insulin, stimulants, or anything marketed as an "active spray" or topical weight-loss compound — if you have seen products described that way, they are unrelated to these prescription medicines. For a closer look at the full components, the pages on what goes into Mounjaro's formulation and the role of tirzepatide as Mounjaro's active substance go into more detail.

Knowing what is in your medicine is a useful starting point — but staying consistent with your weekly injection schedule is what makes the difference over time. GLP Trackr's dose and injection logging feature lets you record every shot: the date, the dose strength, and the injection site. Over weeks, that creates a clear, timestamped record of your treatment that you can bring to your next prescriber appointment.

The app's side-effect tracker is equally useful here. If you notice a reaction and want to understand whether it is linked to a particular ingredient or dose stage, logging how you feel after each injection gives you a pattern to discuss with your healthcare professional — rather than relying on memory.

For a broader overview of everything Mounjaro involves, the Mounjaro guide is a good place to explore, and the Mounjaro ingredients list page offers a more detailed breakdown.

Any concern about a specific ingredient — including a suspected reaction — should be raised promptly with your prescriber or doctor. If you experience a serious or unexpected reaction, contact your healthcare professional without delay and report it to your national pharmacovigilance scheme (such as the UK's Yellow Card scheme) as directed in your patient information leaflet. GLP Trackr records what you log; it is a companion to your clinical care, not a substitute for it.

Ready to keep a clear record of every dose and how you feel after each one? Download GLP Trackr on the App Store or Google Play — your first 7 days are completely free.