How to tell how many doses are left in your Mounjaro pen

Step 1, Find the dose counter before you inject

Hold the pen with the needle cap pointing away from you and the label facing up. About halfway along the barrel, you will see a small clear window with a number printed inside. That number tells you exactly how many doses remain in this pen.

A new, unused pen shows 4. After your first injection it will show 3, then 2, then 1, then 0. The mechanism is mechanical, not digital, no battery, no connectivity, nothing to charge. It simply advances each time the pen completes a full injection cycle.

A question our prescribers hear most weeks is whether the counter can stick or skip. In normal use it should not. If the number does not change after what felt like a complete injection, check the patient information leaflet available via the eMC and contact your prescriber or a pharmacist before injecting again. Do not assume the dose was missed and inject a second time.

Step 2, What to look for if the number is hard to read

Lighting and angle matter more than people expect. Tilt the pen so natural or overhead light falls directly on the counter window. Some patients find it easier to read against a white background. The numbers are printed clearly in black, if you are seeing anything ambiguous, the most common cause is poor lighting rather than a faulty counter.

If you wear reading glasses, keep them on for this step. The window is small, and the difference between a 1 and a 0 matters. At 0 the pen is empty; injecting from an empty pen delivers no tirzepatide, and you may not feel any difference during the injection attempt.

Details on what the pen looks like at each stage are covered in the patient information leaflet that comes in your Mounjaro box. The Mounjaro treatment overview on our site also explains how the KwikPen works in plain terms.

Step 3, Tracking across your treatment cycle

Because one pen lasts four weeks, tracking is straightforward: pen 1 covers weeks 1–4, pen 2 covers weeks 5–8, and so on. Many patients mark the start date on the box with a pen. Others set a weekly phone reminder for injection day, which doubles as a prompt to check the counter before and after.

If you are moving between doses (for example, from 5mg to a higher strength) your new pen starts at 4 again, because the counter is dose-count-based, not a continuation of a previous pen. The strengths differ; only your prescriber decides when a dose change is appropriate. You can read about the individual dose stages, including what to expect at the 5mg stage, separately.

When you are on your last dose (counter showing 1), that is a practical signal to check your supply situation, and our page on how to interpret the dose left in your Mounjaro pen walks through exactly what to do at that point. Private treatment through a regulated pharmacy like our GPhC-registered service requires a clinical re-review before each repeat order, so factor that into your timeline. Our GPhC premises registration is publicly verifiable at the GPhC register.

Storage, disposal and a note on the reservoir

One thing worth knowing: the liquid level visible through the pen's side does not tell you how many doses remain. The reservoir is designed so that a small amount of liquid is always present even after the counter reaches 0. Judging doses by eye is unreliable; the counter is the only accurate guide, and the NHS tirzepatide medicines page reinforces that patients should follow the manufacturer's instructions for the device.

Store the pen in the fridge (2–8°C) until you are ready to use it. For the exact window allowed for room-temperature storage before an injection, check your patient information leaflet; the SmPC details vary slightly by strength, and we do not publish a single figure here because the wrong number could mislead. Dispose of used pens in a sharps container, not household waste.

If you have broader questions about how many doses a particular strength contains, our guide on how many doses come in a Mounjaro pen covers the full breakdown. Questions about cost and what a private prescription includes are covered on the Mounjaro prices page. And if something about your treatment feels off, the right step is always to speak with your prescriber rather than adjust anything yourself.

If you are not yet on treatment and are exploring whether Mounjaro might be clinically suitable for you, patients who have already started on the lowest strength may find it useful to read through UK reviews of the Mounjaro KwikPen 2.5mg before their first injection, and you can check your eligibility with a free consultation, reviewed the same day by a GPhC-registered prescriber.