What to Do If Your Tirzepatide Pen Has Expired

Step 1, Find and read the expiry date correctly

The expiry date on a Mounjaro KwikPen appears in two places: on the pen label itself and on the outer carton. It is expressed as month and year (MM/YYYY). A pen dated, say, 06/2025 is valid through the last day of June 2025, it expires at midnight on 30 June, not on the first of the month. This trips people up more often than you might expect.

There is a second date to watch. Once you remove the cap and take your first dose, the pen has entered its in-use period, which is governed by a separate, shorter timeframe regardless of what the printed date says. The exact in-use window depends on whether the pen has been kept refrigerated or stored at room temperature, and those figures are set out in the tirzepatide pen guide alongside the general storage rules. For the precise numbers, always go to the Patient Information Leaflet that comes with your pen, or contact our clinical team if you are unsure.

If the printed date has passed and the pen is unused, it is expired. If it passed while the pen was in active use, it is also expired. Either way, the answer is the same: do not inject it.

Step 2, Dispose of the expired pen safely

A common misconception is that blunted or used pens can go into the household waste if the needle is recapped. They cannot. An expired or used tirzepatide pen is a sharps item regardless of whether it has been injected, and it must go into a yellow sharps bin.

In the UK, many GP surgeries and community pharmacies accept pre-filled sharps containers for disposal free of charge, it is worth phoning ahead to confirm. Your local council's household waste pages will also list sharps collection points or bin-swap services. A 1-litre sharps container is adequate for most patients managing a single pen at a time.

Never place a pen in recycling. Never try to remove the needle manually. The needle mechanism on the KwikPen is designed not to be disassembled by the patient, and attempting to do so risks needlestick injury. If you have questions about disposal in your area, the nume FAQs cover the basics, or you can reach our team directly.

Step 3 (Understand what expiry actually means for the medicine

Tirzepatide is a peptide medicine) a chain of amino acids. Like most biologics, it degrades gradually over time, and the expiry date is the manufacturer's guarantee that the medicine remains within its licensed potency and purity window up to that point. After that date, Eli Lilly no longer certifies it.

In practice, degradation does not make the pen obviously different. The liquid does not change colour; there is no smell. This is precisely why the date matters: you have no sensory way of telling whether a given dose is full strength or partially degraded. Injecting an under-potent dose is not a neutral act, it may mean a week's worth of appetite regulation and glucose signalling is compromised, and if you are on a titration schedule, it may complicate how your prescriber interprets your progress. You can read more about how the medicine works on the Mounjaro overview page.

For a broader look at the specific rules governing tirzepatide expiry dates (including the in-use versus sealed-pen distinction) that page goes into the detail, and if you are also wondering whether tirzepatide expires and what that process involves, that question is covered there in full.

Step 4, Replace the pen and keep your schedule on track

Once you have disposed of the expired pen, the priority is getting a valid replacement as quickly as possible. Skipping a dose is not ideal (consistent weekly dosing is part of how the medicine maintains its effect) but injecting an expired pen is not an acceptable workaround. Contact your prescriber or pharmacy promptly.

If you are a nume patient, our clinical team is available seven days a week through the contact page. If your situation involves a missed dose because of the expired pen, do not adjust your next dose yourself, a prescriber will advise on timing. The NHS tirzepatide guidance also covers what to do when a dose is missed, and your Patient Information Leaflet is the definitive reference.

For anyone thinking about whether the risks of using an expired Mounjaro pen are really that significant, that page addresses the question directly. The short answer is that the risk is real enough not to take. On the subject of cost (replacing a pen is an expense nobody wants) the Mounjaro price context page explains what private treatment typically includes, and how to read a quote that is all-in versus one that is not.

When you are ready to continue treatment or start afresh, you can start a free consultation with our prescribers. Every review is done by a named GPhC-registered Independent Prescriber (the same day, on working days) and delivery follows by tracked DPD the next working day once approved.