How to count the doses left in a Mounjaro KwikPen

By Ümit Can Erim · Published 4 November 2026 · Updated 4 November 2026 · Sources checked 4 November 2026 · How these guides are written

A Mounjaro® KwikPen® holds 4 weekly doses, and its instructions describe no counter that shows how many remain. So you count them yourself: note the day of the first dose, then tick off each injection. The pen is finished after the fourth dose or 30 days after first use, whichever comes first, even if you can still see medicine inside.

Read this first. This page reports what the published instructions say. It cannot tell you whether a particular dose went in or whether your pen is still fit to use. If you cannot remember whether you took this week's dose, ask your pharmacist or prescriber before you inject again.

What ends a KwikPen

The US, UK and Canadian instructions agree on the first two limits below. The US prescribing information also lists the room-temperature total as a limit of its own.

Limit	What the instructions say
4 weekly doses	Throw the pen away after the fourth dose, including the unused medicine
30 days after first use	Throw it away, even if there is medicine left in it
30 days in total at room temperature	US label: room temperature means up to 30 °C (86 °F)
Frozen	Throw it away, whatever else is true of the pen

Why you cannot read the count off the pen

The dose window shows two things in the instructions: the prime position and the full-dose icon. Neither one is a number of doses left. The UK instructions go further and mark lines on the pen with the words "Do not use these marks as dose indicators".

The liquid you can see does not help either. The US label says each KwikPen contains additional volume to allow for priming, and the Canadian instructions say the leftover medicine after the fourth dose is normal and helps the pen work correctly. A pen that looks part full can be finished.

How to keep count

Write down the day of the first dose. Add 30 days to it and write that date down too. That is the last day of this pen.
Use the calendar in the instructions. The US, UK and Canadian instructions each end with a Medication Calendar, with space for the dates you inject.
Tick it off straight after the injection. A tick added on the day is a record. A tick added a week later is a guess.
After the fourth tick, the pen is done. Throw it away as your pharmacist or the instructions describe, and start the count again with the next pen.

Here is the arithmetic for a pen first used on 1 March. Your own day is whichever one your prescriber set.

Dose	Date	Doses left afterwards
1st	1 March	3
2nd	8 March	2
3rd	15 March	1
4th	22 March	0: throw the pen away
30-day limit	31 March	Not reached in this example

When the 30 days arrive first

On an unbroken weekly schedule the fourth dose falls 21 days after the first, so the 30-day limit stays out of the way. A gap changes that. Skip one week and the fourth dose falls on day 28 after the first. Skip two and it would fall on day 35, past the limit, so the pen ends with a dose still in it.

The arithmetic stops there. Whether to take a late dose, and what to do about a gap in treatment, are questions for your prescriber. What the leaflets say about a missed dose is a separate page. Lilly's Canadian FAQ is direct about the limit itself: its in-use testing supports 30 days, and use beyond that is not recommended.

The medicine left at the end

It is not a fifth dose. The US instructions say the pen will prevent you from dialing a full dose after 4 weekly doses, and warn that "attempting to inject any leftover medicine could result in an incomplete dose". They also say not to transfer the medicine into a syringe.

If the dose knob will not turn all the way to the full-dose icon, the instructions say to throw the pen away with the medicine in it, because there may not be enough for a full dose. If that happens before your count reaches four, tell your pharmacist: you are a dose short and they can advise on what comes next.

Check that yours is a KwikPen

Everything above is about the multi-dose KwikPen. A single-dose Mounjaro pen holds one dose and is discarded after it, and the US label gives it a different limit of 21 days in total at room temperature. That is the tirzepatide figure in our storage guide. The name of the device is on your carton.

Dozify keeps the count for you

Add your pen as a KwikPen and My Stock shows the doses left and the expiry date. Each shot you log takes one dose off the pen, and the home screen tells you before you run out. This is part of Premium; dose logging and reminders stay free.

Download the app See how stock tracking works →

Questions

How many doses are in a Mounjaro KwikPen?

Four fixed doses, one taken each week. That is the same at every strength from 2.5 mg to 15 mg: the strength printed on the pen is the size of each dose, not the amount in the whole pen.

Can I get an extra dose from what is left?

The instructions say no. Do not inject the leftover medicine and do not draw it into a syringe, since it could be an incomplete dose.

Do I prime the pen every week?

Yes. Priming is one of the steps in the instructions for each injection, and the extra volume in the pen is there to allow for it. It does not count as one of your 4 doses.

I lost count. What now?

Ask your pharmacist or prescriber, and tell them the date of the first dose if you know it. Do not inject again just to be sure: for a dose you think was incomplete, the instructions say not to start over or repeat the injection.

Can an opened KwikPen go back in the fridge?

The US prescribing information lists both the refrigerator and room temperature up to 30 °C (86 °F) for a pen in use, and the 30-day limits still apply. Follow the instructions that came with your own pen, since wording differs between countries.

Does this apply to the Zepbound KwikPen?

The Zepbound® US prescribing information also lists a KwikPen with four weekly doses and the same discard rule. Check the instructions in your carton.

Educational information, not medical advice. Dozify is a personal tracking app, not a medical device. This page reports public drug labelling and does not recommend a medicine, a dose or a schedule. Mounjaro®, Zepbound® and KwikPen® are trademarks of Eli Lilly and Company; Dozify is not affiliated with Lilly. Always follow the instructions that came with your medication, and ask your pharmacist or prescriber when you are unsure.