Mounjaro Pen Stuck? What to Do (November 2026)

01 · Do this first

What to do the moment your Mounjaro pen is stuck

The first thing to do is stop pressing. Pushing harder on a button or dial that is not moving is the one action most likely to turn a small problem into a wasted pen or an inaccurate dose. Take a breath, put the pen down somewhere safe, and work through the checks in order.

Next, think about the pen itself.

If the pen is not empty, look at the needle and how it was attached, and read the pen's patient information leaflet, which sets out how to attach a needle and what to do if the pen does not work as expected.¹³ Our step-by-step guide to how to unjam a Mounjaro pen goes through the practical handling checks in more detail.

02 · Diagnose it

Is the pen stuck, or is it empty?

Tell the two apart by what the dose window shows and how the dial behaves. A pen that is empty or nearly empty behaves differently from a pen with a blocked needle, and the right response is different too. The table sets out the common patterns and a safe next step for each.

If you cannot say with confidence what is wrong, the safest course is to leave the pen alone and ask.

03 · Next decision

When to contact the pharmacy or prescriber

Contact us or your prescriber whenever the pen will not deliver a full, confirmed dose. A faulty pen is a supply problem, not something to solve by improvising. Dispensed prescription medicines cannot be returned except when faulty, damaged or the wrong item, so tell us promptly if you think the pen is defective.

Our support team is available Monday to Friday, 9am to 5pm, by email at support@everydaymeds.co.uk, through the account portal chat or by phone on 0333 207 0413. Tell us what the dose window shows, which dose you are on, when you last injected and what you have already tried. That lets us advise quickly and helps your prescriber decide on next steps.

If you are not yet a customer and are comparing providers, you can see current options on the Mounjaro pen prices and consultation page. The standard price of the starting pen is £169.99 per month, and all six doses are in stock. Prices checked 11 November 2026.

If your problem is that the needle itself seems fixed to the pen, see our page on a needle that will not come off the pen. If the pen is stuck at the end of its supply, see what happens on the last dose.

04 · How the KwikPen works

How the Mounjaro KwikPen is designed to work

Mounjaro is the brand name for tirzepatide, a once-weekly injectable prescription medicine made by Eli Lilly. In the UK it is licensed for weight management in adults and for type 2 diabetes. It comes as a pre-filled multi-dose pen (KwikPen) in six strengths: 2.5mg, 5mg, 7.5mg, 10mg, 12.5mg and 15mg.¹ Understanding that a single pen is built to be used across several weekly injections explains a lot of the confusion people have when it appears to stop working.

The pen is not a syringe you fill. It is a sealed device with a dose knob, a dose window and an injection button. That detail matters because many people assume the pen is broken when the clicks feel different from last week. Clicks are not the measure; the number in the window is.

Each KwikPen contains four weekly doses.¹³

Because the mechanism relies on the window reading correctly, a few simple habits reduce problems. Keep a note of the date of each injection so you always know where you are in the pen. Turn the dose knob steadily rather than jerking it. Read the window in good light before you press the button. And if anything looks unusual, such as a number that will not settle or a knob that resists, pause rather than push through.

It also helps to remember that the dial is part of the dose check, not an obstacle. When it stops where you do not expect, it is giving you information. Our guide to preparing your Mounjaro pen covers the routine before each injection, and a calm, repeatable routine is the best protection against the panic of a pen that seems to have jammed.

Finally, remember that the pen is a prescription device supplied for one person. If you are unsure whether something is a fault or a normal feature, we would always rather you asked than guessed. A short message to the pharmacy costs nothing and can save a wasted dose or an unsafe injection.

05 · Stuck on zero or empty

Pen stuck on zero: finished, not jammed

A pen that shows zero and will not dial is very often a pen that has done its job.

The honest answer is that the design limits you to the medicine inside, rather than switching off on a count. Each KwikPen contains four weekly doses.¹³ If you have injected the doses you were supplied for, the pen reaching its limit is the expected outcome, not a defect.

Before concluding the pen is empty, count back through your injection dates. If you started a new pen recently and have not yet injected the number of weekly doses it holds, something else may be wrong, and you should contact us. If you have used the full number, you need your next pen rather than a repair. Our page on a pen stuck on the last dose looks at that end-of-pen situation specifically.

What you should not do is try to squeeze out whatever is left. If the pen cannot deliver the full dose you are due, you need a new pen, and the pharmacy can help you arrange it.

Plan ahead where you can. If you are nearing the end of a pen, check that your next supply is on its way before your injection day, so you are not caught out with a pen that will not dial and no replacement. Repeat orders with us re-check suitability and there is no auto-shipping, so you will need to place the order yourself in good time. Free next-day tracked delivery in temperature-controlled packaging is included, and same-day dispatch applies when you order by 3pm.

06 · Needle and button problems

Needle and injection button problems

If the pen dials correctly but the injection button will not press, the needle is the first thing to suspect. A needle that is not fitted correctly, or one that has become blocked, can make the button feel stuck. The patient information leaflet sets out how to attach a needle and what to do if the pen does not work as expected, and that leaflet is the authority to follow.¹³

Online forums are full of tips for freeing a jammed pen, and some of them involve force, tapping, shaking or dismantling the device. None of that is safe to try. If a needle problem is suspected, stop, set the pen aside and ask for advice rather than experimenting with the mechanism.

Needles, a sharps bin and injection guidance are included with every order, so you should have what you need to follow the leaflet properly. Dispose of used needles in the sharps bin, not in household waste. If a needle seems fixed to the pen or will not come away, our page on a needle stuck on the pen covers that separate problem.

It is worth thinking about what changed since your last injection. Did you use a different needle? Did you attach it in a hurry? Did the pen spend time somewhere cold or hot? Was it dropped or knocked in a bag? Any of these can matter. When you contact us, giving that history helps the prescribing team judge whether the issue is a handling problem or a faulty pen.

Also avoid the temptation to keep trying repeatedly. Each attempt risks delivering part of a dose, and you may not be able to tell how much went in. If you are unsure whether a dose was delivered, do not simply inject again to be safe. Contact your prescriber or the pharmacy and describe exactly what happened. They can advise on timing in line with the missed-dose rule rather than leaving you to guess.

Finally, if there is any visible damage to the pen, such as a cracked body, a loose component or leaking medicine, do not use it. A damaged pen is a reason to ask for a replacement, and the faulty or damaged item route is exactly what our returns policy covers.

07 · Why you should not force it

Why forcing a stuck pen is the wrong move

Forcing a stuck pen can damage the mechanism and compromise the dose you receive. The pen's accuracy depends on the dial and plunger working as designed. When you push through resistance, you can no longer be confident that what the window showed is what you injected. That uncertainty is the real risk, more than the wasted medicine.

A half-delivered injection from a jammed pen leaves you unsure what dose you received, which is why the right response is to stop and ask.

The licensed ladder already starts low for tolerability. Everyone starts Mounjaro on 2.5mg once a week, and the dose can step up by 2.5mg at a minimum of four-week intervals up to a maximum of 15mg weekly, depending on how you respond and tolerate it.¹ If a pen problem leaves you uncertain about the dose you have had, speak to your prescriber. Do not try to make up the difference yourself.

If a pen is faulty, tell us promptly so the item can be dealt with under our faulty, damaged or wrong item policy.

Equally, do not share pens or borrow one from a friend to get over a gap. Mounjaro is prescribed to an individual after a consultation reviewed by a GPhC-registered prescriber, and pens are not interchangeable between people. Our page on sharing a Mounjaro pen explains why that is unsafe.

08 · Storage and handling

Storage and handling that affect how the pen works

Storage mistakes are an under-recognised reason for a pen that behaves oddly. Keep Mounjaro pens in a fridge at 2–8°C and never freeze them. Once in use, a pen can be kept out of the fridge at a temperature not above 30°C for up to 30 days after first use, and must then be thrown away. Keep the pen cap on to protect it from light, and never use a pen that has been frozen.¹³

If your pen feels different, ask whether it has been stored properly. A pen pushed to the back of a fridge where it can freeze, left in a hot car or kept in a bag next to an ice pack may not be safe to use, whatever it feels like in your hand. If there is any chance it was frozen, do not use it and contact the pharmacy.

When travelling, carry pens in hand luggage, because hold luggage can fall below freezing, ideally in a cool bag with the prescription label or a copy of your prescription. In-use pens tolerate up to 30 days not above 30°C, so most holidays need no special arrangements. For hot climates, use an insulated pouch.¹ A knock in a packed suitcase is a common cause of damage, so keep the pen in a protective case rather than loose.

Unopened pens should be kept in the fridge and keep until the expiry date printed on the box. If an unopened pen has been out of the fridge, check with the pharmacy before using it rather than relying on a remembered day limit, because figures circulating online often come from other countries' labels.¹³ That is especially relevant if a pen seems stiff and you are wondering whether it spent too long on a warm doorstep.

Good habits help: take the pen out of the fridge only when you are ready to inject, check the window and the pen body for damage, and return it to appropriate storage afterwards. If the pen is new, our guide to preparing a Mounjaro pen walks through the routine.

09 · Needle-stick accidents

If you are accidentally pricked by a needle

A stuck pen often means fiddling with a needle, and that is when accidental pricks happen. If you are accidentally stuck by a needle, deal with it calmly and get proper advice rather than relying on a general web search. We are a pharmacy, not an emergency service, and we cannot assess an injury remotely, so the right place to turn is a pharmacist, your GP or the NHS urgent advice services.

The circumstances change what is sensible. A prick from your own clean, unused needle is very different from a prick from a needle that has been used on someone else. If the needle belonged to another person or came from a shared or unknown source, seek medical advice promptly and tell the clinician exactly what happened. Do not wait to see whether symptoms develop.

For Mounjaro, the needle is attached to the pen as described in the patient information leaflet, and the leaflet is the place to check how to attach and remove it correctly.¹³ Do not pull a needle out of its hub or cut it, and do not recap it with force. If a needle will not come away normally, ask for help rather than improvising.

Always put used needles in a sharps bin, which is included with every order. Do not leave loose needles where children, pets or other household members can reach them. When the sharps bin is full, follow your local arrangements for disposal.

If you notice an unexpected symptom after a pen problem or a needle accident, tell your prescriber; for severe or persistent stomach pain, chest pain, swelling of the face or throat or difficulty breathing, get medical help straight away. You can also report suspected side effects through the MHRA Yellow Card scheme.¹⁹ Reporting helps regulators spot patterns with devices as well as medicines, which is how faults in pens get picked up and addressed.

Finally, if a needle problem leaves you unsure whether you received your dose, do not inject again straight away to be safe. Describe what happened to your prescriber or pharmacist and follow their advice, which will take the missed-dose rule into account.

10 · Missed doses and timing

If a stuck pen makes you miss your injection day

A faulty pen can leave you without a usable dose on your usual day, and the missed-dose rule tells you what to do. If you miss a dose, take it as soon as you can within 4 days (96 hours) of the scheduled time, then carry on with your usual day. If more than 4 days have passed, skip the missed dose entirely and take the next one on your normal day — never take two doses within 3 days of each other.¹

That gives you a reasonable window to sort out the pen. Contact the pharmacy as soon as you realise there is a problem, rather than waiting until the end of that window. Delivery of a replacement takes time, and the sooner we know, the sooner we can help.

You can also change your weekly injection day if needed, as long as at least 3 days (72 hours) have passed since your last dose.¹ If a replacement pen arrives on a different day from your usual one, your prescriber can advise on your injection day.

There is no best time of day to inject. Mounjaro works the same morning or evening, with or without food, and what matters is the same day each week.¹ So a delayed dose on a different time of day is not a problem in itself; the key is staying inside the missed-dose limits and not doubling up.

Do not try to compensate for a missed or uncertain dose by injecting extra later. Never take two doses within 3 days of each other. If you cannot work out whether you are inside or outside the window, ask your prescriber.

It is also worth knowing that tirzepatide has a half-life of about five days, so after a final dose it takes roughly four to five weeks to clear the system. A short delay while you sort out a pen is therefore not a sudden stop, but speak to your prescriber before restarting.

Many people on a stuck-pen day are worried about progress too. Weight loss on Mounjaro is gradual by design, and you should think in months, not days. A short delay will not undo your progress, and you should judge results by trend rather than individual weigh-ins. If you are concerned about a plateau, our page on weight stuck on Mounjaro looks at that separately.

11 · Getting a replacement

Getting help and a replacement pen

The practical route to a working pen is to contact the pharmacy that supplied it. We dispense Mounjaro from official LillyDirect supply, sourced from Eli Lilly's UK distribution, and the pens we supply are genuine KwikPens. If you believe your pen is faulty or damaged, tell us straight away with a description of the problem, the dose on the label and the date of your last injection.

Our service is built around ongoing support. Prescriber reviews, dose-titration and follow-up assessments are part of the aftercare, along with side-effect support. A reviewed pen problem is part of that conversation, because your prescriber needs to know whether you have had your full dose each week. Repeat orders re-check suitability, and there is no auto-shipping, so you remain in control of when the next pen is dispatched.

Delivery is free, next-day and tracked, using temperature-controlled, discreet packaging. Same-day dispatch applies when you order by 3pm. Saturday delivery is £14.99. If you are replacing a pen on a tight schedule, factor that in and place your order early enough.

Everything we supply is prescribed after a free online consultation reviewed by a GPhC-registered prescriber, and the consultation is free with no hidden fees. Payment is taken when you place the order; if the prescriber decides the treatment is not suitable, the order is refunded automatically in full. You can pay by Visa, Mastercard, Klarna or pay-monthly options, and there are no subscriptions. To see current options, visit the Mounjaro pen page, or explore our wider weight loss clinic.

For more practical tips, our guides on handling tips for a stuck pen and how the pen mechanism behaves offer additional context. Mounjaro (tirzepatide) is a prescription-only medicine, used alongside a reduced-calorie diet and increased physical activity. Individual results vary. This page is information, not a substitute for medical advice.