You've dropped your Mounjaro pen — here's exactly what to check

The moment after it hits the floor

It happened fast, the pen slipped off the bathroom shelf or rolled off the kitchen counter, and now you're holding it wondering whether tonight's injection is still on. Take a breath. The first thing to do is nothing: don't recap, don't press any buttons, don't try the injection yet. Place the pen on a flat surface and start a calm visual check.

Look at the cartridge window. The solution inside should be clear and colourless, essentially water-clear. If it looks cloudy, discoloured or contains visible particles, set the pen aside, that pen should not be used. A crack in the cartridge or the outer casing is also a clear signal to stop; even a hairline crack can compromise the sterility of the medicine inside.

If the pen had a needle attached when it fell, be careful around the tip. The needle on a Mounjaro pen should be replaced with a fresh one before each injection anyway, so this is a good moment to remove it using the outer cap and dispose of it in a proper sharps container. A bent or visibly damaged needle is an additional reason to pause and assess before proceeding.

What a fall can (and cannot) do to the pen mechanism

There's a common worry that a dropped pen will miscount its doses or fire a partial injection unexpectedly. The Mounjaro KwikPen uses a mechanical click-and-hold delivery mechanism, and dropping the pen on its own does not trigger a dose, the button still needs to be pressed and held deliberately. So a fall doesn't mean you've accidentally injected yourself or wasted a dose through the air.

What a hard drop can do is damage the cartridge internally or disturb the plunger mechanism in ways that aren't visible from the outside. If the pen landed needle-end down with force, there is a small chance the stopper inside has shifted. This is where a close look at the dose counter matters: if the number shown has changed from what it was before the pen fell, something may have moved and the pen should not be used.

For detailed guidance on how the pen is designed to work under normal conditions, the step-by-step pen use guide is a useful reference. The Mounjaro patient information leaflet, available through the Mounjaro SmPC on the eMC, also describes what a normal cartridge looks like and the checks to carry out before injecting.

Storage, temperature and what happens if the pen was unrefrigerated before the drop

Mounjaro pens are stored in the fridge at 2–8°C, so a pen that falls and rolls under a sofa for twenty minutes has two potential problems: the drop itself and the fact it left the fridge. The SmPC and patient information leaflet set out exactly how long the pen can be kept at room temperature once removed from refrigeration, always check those documents for the precise window rather than relying on memory or secondhand advice, because the allowance is specific and time-limited.

If the pen looks undamaged after your inspection, the solution is clear, the dose counter is unchanged, and you're within the room-temperature limit described in the leaflet, the injection can typically proceed normally. Attach a fresh needle, follow your usual technique, and rotate the injection site as you normally would. The Mounjaro injection overview covers site rotation and technique if you want a reminder.

One misconception worth laying to rest gently: some people assume that any jar or knock means the medicine has been somehow deactivated or changed chemically. In practice, the concern with a drop is physical (a crack, a leak, a bent needle) not a change to the medicine's chemistry from the impact itself. If everything looks right, it usually is. Our guidance on what to do with a used Mounjaro pen may also be helpful once you've completed your injection and are ready to dispose of it safely.

When to contact your prescriber or pharmacy

If any part of the inspection gives you pause (the solution looks off, you can't confirm the dose counter reading, the casing feels cracked, or you simply aren't sure) don't inject. Contact the team who prescribed your treatment. At nume, aftercare is available seven days a week, and our prescribers can advise on your specific situation rather than a generic answer.

A concern about a damaged or dropped pen is exactly the kind of thing aftercare exists for. If you decide to arrange a replacement pen, a prescriber will review your situation before it's issued. There's also a full FAQ section covering common practical questions about your treatment, including how the tirzepatide pen injector is designed to be handled and what its key components do.

For anything that feels like an urgent medical concern (a needle-stick injury, signs of an allergic reaction, or accidental injection of a damaged pen) contact NHS 111 or your GP rather than waiting for a pharmacy response. Side effects from Mounjaro, including any unexpected reactions, can be reported directly to the MHRA through the Yellow Card scheme.

If you're new to treatment or want to understand the full range of what's available, our free consultation is the place to speak to our prescribers.