What has changed with the Mounjaro KwikPen?
The pen has small visual and structural changes. They make it clearer when all four fixed doses have been delivered, and reduce confusion about leftover liquid.
Important: the medicine itself hasn't changed. The update doesn't change how tirzepatide works, your prescribed dose, your dose strength or your weekly injection routine.
Why has the pen been updated?
In the modified pen, the plunger starts slightly lower in the cartridge, and an extra internal component lets it travel further by the fourth injection. This reduces uncertainty about whether any usable medicine is left.
These are device improvements only. They don't affect the strength, safety, quality or effectiveness of your treatment.
How the Mounjaro KwikPen works
Both the original and modified pens are disposable, pre-filled, multi-dose pens for one person. Each pen contains:
- four fixed 0.6ml doses
- one dose taken once a week, as prescribed
- a little extra liquid used for priming before each injection
Differences you may notice
1. Plunger position
Before first use, the plunger in the modified pen may sit slightly further down the cartridge than in the original.
2. Extended internal plunger
A new internal component lengthens the plunger, so it moves closer to the end of the cartridge after the final dose.
3. Clearer finish after the fourth dose
After the fourth dose, the plunger sits nearer the end of the cartridge, making it clear the pen is empty and ready to throw away.
| Original KwikPen | Modified KwikPen 2026 | |
|---|---|---|
| Medicine | Tirzepatide | The same tirzepatide |
| Doses | Four fixed 0.6ml weekly doses | Four fixed 0.6ml weekly doses |
| Routine | Once weekly, as prescribed | Once weekly, as prescribed |
| Appearance | Some liquid may be visible after the fourth dose | Clearer that the fourth dose is complete |
What happened to the "golden dose"?
Some people noticed a little liquid left in older pens after the fourth injection, sometimes called the "golden dose". The pen has always been designed to deliver four fixed doses only. The remaining liquid was there for priming, not an extra dose.
Don't try to use leftover liquid. Use the pen only as described in the leaflet and Instructions for Use supplied with your medicine.
Will the new pen change how I inject?
No. The injection technique, medicine and weekly schedule are the same. Keep following the Instructions for Use supplied with your pen. If you're unsure, ask your prescriber before your next dose.
Why might I get different versions?
There's no single changeover date. Existing stock of the original pen is still being used, so you may receive either version while supplies change. A different-looking pen doesn't mean your prescription has changed.
Safety and reporting
If you're worried about your pen, your dose, possible side effects or whether the pen worked properly, contact your prescriber. Suspected side effects and product problems can be reported through the MHRA Yellow Card scheme, or to Lilly UK on 01256 315 000.
Talk it through with a prescriber
Start with our free online consultation. Before any treatment starts, you'll have a video consultation with a pharmacist or nurse prescriber, who will recommend what's safest for you.
Start free consultationFrequently asked questions
Has the Mounjaro medicine changed?
No. The 2026 update is to the KwikPen device only. The medicine, tirzepatide, is unchanged.
Does the new Mounjaro pen contain fewer doses?
No. Both the original and modified pens deliver four fixed weekly doses.
Will my Mounjaro dose strength change?
No. The update doesn't change your prescribed strength, dose plan or injection day.
Can I use leftover liquid in a Mounjaro pen?
No. The pen delivers four fixed doses only. Leftover liquid is for priming and isn't an extra dose.
Is it normal to receive the old pen and then the new one?
Yes. Both versions may be supplied while existing stock is used up.
References
Last reviewed: October 2026. This guide is general information and doesn't replace advice from your prescriber or the leaflet supplied with your medicine.