Brand · tirzepatide
Mounjaro
Last reviewed · Written by the PepCycle team
Mounjaro is the brand name for tirzepatide licensed for type 2 diabetes. Tirzepatide is a dual GIP and GLP-1 receptor agonist, injected once weekly. Mounjaro contains the same active ingredient as Zepbound but is a separate product with its own indication and labelling.
What Mounjaro is
Mounjaro is tirzepatide approved for use in adults with type 2 diabetes to improve glycaemic control alongside diet and exercise. It is administered as a weekly subcutaneous injection and manufactured by Eli Lilly.
Because tirzepatide activates both incretin receptors rather than GLP-1 alone, it is not simply "another Ozempic" — the pharmacology differs, and so do the trial data. Which product suits any individual is a clinical decision, and this page takes no position on it.
Pens, vials and the confusion between them
Mounjaro has been supplied as a single-dose auto-injector pen and, in some markets and programmes, as a manufacturer-filled single-dose vial used with a separate syringe. The vial format is the one that causes trouble in peptide-tracking apps.
- Pen: record product, strength, lot, date and time. Nothing is derived.
- Vial: record the stated amount, the syringe used and the date. Still nothing is derived.
- Both: record the injection site and rotate.
For the full distinction, see pens versus vials.
What a useful record contains
- Product name, strength and lot as printed.
- Actual injection date and time — weekly schedules drift silently.
- Injection site, rotated and recorded.
- Titration changes as dated events with the instructing clinician.
- Side effects with timestamps, particularly gastrointestinal effects in the days following an injection.
- Glucose readings or weight on a consistent schedule, so trends are comparable.
PepCycle keeps injections, measurements and side effects on one timeline, exportable to CSV or JSON for a review appointment.
Mounjaro and Zepbound
| Mounjaro | Zepbound | |
|---|---|---|
| Active ingredient | Tirzepatide | Tirzepatide |
| Licensed for | Type 2 diabetes | Weight management (plus OSA in some markets) |
| Manufacturer | Eli Lilly | Eli Lilly |
| Interchangeable? | No — separate products and labelling | No |
A switch between them is a product change, and belongs in a log as a new compound with a start date rather than a rename of the old one.
Frequently asked questions
Is Mounjaro a GLP-1 medication?
It contains tirzepatide, which activates both the GIP and GLP-1 receptors. Calling it a GLP-1 is common shorthand, but it is a dual incretin agonist rather than a pure GLP-1 receptor agonist.
Do I reconstitute a Mounjaro vial?
No. A manufacturer-filled Mounjaro vial contains a finished solution at a fixed concentration. Reconstitution applies only to lyophilised powder that you dissolve yourself, which this is not.
What is the difference between Mounjaro and Zepbound?
Both are tirzepatide from Eli Lilly. Mounjaro is licensed for type 2 diabetes and Zepbound for weight management, with obstructive sleep apnoea added in some markets. Separate products, separate labelling, not interchangeable.
How should I log a weekly injection I took a day early?
With its actual date and time, flagged as off-schedule. The value of the record is that it shows the real interval; adjusting the entry to match the plan defeats the purpose.
Related pages
Keep a Mounjaro record your prescriber can read
Log every injection with its real date and time, mark late and missed entries instead of hiding them, record side effects alongside dose changes, and export the whole timeline before an appointment.
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