Mounjaro Froze in the Fridge: What to Do Next (October 2026)

01 · Do this first

What to do if your Mounjaro froze in the fridge

Do not inject it, whatever it looks like now. The storage guidance for Mounjaro says to keep pens in a fridge at 2–8°C and never freeze them, and it says never use a pen that has been frozen.¹³¹ That instruction has no exceptions for pens that have thawed and look clear again.

Here is a sensible order of action:

• Stop and set the pen aside. Do not try to warm it, shake it or test it with a trial injection.
• Check the other pens. If you keep more than one pen, check each of them. A cold spot in the fridge can affect everything stored in the same place.
• Dispose of the frozen pen safely. Put it in a sharps bin, in line with the pen's instructions. Do not put it in household rubbish.
• Contact your pharmacy or prescriber. Tell them what happened and how the pen was stored. They can advise on a replacement and on when your next dose should fall.
• Fix the fridge problem before the next pen goes in.

If you ordered from us, contact our support team (Monday–Friday 9am–5pm) and we will talk you through the next steps. Our prescribing team handles dose timing questions as part of ongoing monthly reviews.

02 · Decision guide

Frozen, cold or just cloudy? A quick decision table

Not every worry about a cold pen means it has frozen, but the safe response depends on what you actually found. Use this table as a guide and, if unsure, treat the pen as unusable until a pharmacist has advised you.

If you are not sure whether a pen froze, for instance it was at the back of a very cold fridge but looks fine, call the pharmacy. Telling them the facts costs nothing, and replacing a pen is far better than injecting an unreliable one.

03 · Why you shouldn't use it

Why you should not use a frozen Mounjaro pen

The label tells you never to use a pen that has been frozen, so the decision is made for you.¹³ Mounjaro is a prescription medicine dosed once a week, and each dose matters. If the contents have been through a freeze, nobody can confirm that the pen still delivers the strength printed on its label.

Many people hope a pen that has thawed and looks normal is fine. The trouble is that you cannot see whether a medicine has been affected. A clear liquid is not proof of quality, which is why the guidance is a blanket rule rather than a visual test.

There is also a practical side. A KwikPen is a multi-dose device. If it has frozen, the whole pen is affected, not just the next dose, so you cannot use up what you think is a safe part of it. Treat the entire pen as unusable.

Being wary is not an overreaction. It is the same care you would apply to any prescription injectable. If you are worried you have already injected from a pen that may have frozen, speak to your prescriber or pharmacist, describe what you used and how you feel, and report anything unusual through the Yellow Card scheme.¹⁹ If you have severe, persistent stomach pain, swelling of the face or throat, difficulty breathing or yellowing of the skin or eyes, get medical help straight away.

04 · How pens freeze

How pens end up frozen in a fridge

Pens usually freeze because of where they sit, not because the fridge is faulty. Most domestic fridges are coldest near the back wall, directly against the cooling element, and close to the freezer compartment. A pen pressed against either can drop below the safe range even though the fridge's dial reads normally.

The common causes are easy to spot once you know them:

• Pen touching the back wall or cooling plate. This is the most frequent cause in fridges that build up ice at the rear.
• Storage in the freezer drawer or door by mistake. A shelf labelled for frozen items is the wrong place for any pen.
• Fridge set too cold. If salad leaves, milk or other items are freezing too, the whole fridge is running below the safe range.
• Cold packs placed directly against the pen. This applies in travel bags too.
• Hold luggage on flights. Hold areas can fall below freezing, which is why pens should travel in hand luggage.¹³

Fridge behaviour can also change with the season and with how full the fridge is. A packed fridge blocks airflow, and an empty one can swing in temperature. If a pen froze once, assume the position was the problem and move it before the next pen goes in.

Our own guide to keeping Mounjaro in the fridge covers the practical side of fridge storage in more detail.

05 · Spotting a bad pen

How to tell if a Mounjaro pen has gone bad

Check three things before every injection: how it was stored, how the liquid looks, and the expiry date. Product information describes a genuine UK pen as arriving cold-chain packaged from a registered pharmacy with a batch number and expiry date, with a solution that is clear and colourless.¹³

Do not use a pen that:

• has been frozen, even if it has thawed;
• looks cloudy or discoloured;
• has particles in the solution;
• is past its expiry date;
• has been out of the fridge for more than 30 days, or above 30°C in use.

Do not rely on smell, feel or your own judgement of how cold the pen was. If the history is uncertain, say so to your pharmacist and let them decide.

If supply or packaging ever looks wrong, for example no batch number, no label or packaging that does not seem to have been kept cold, check the pharmacy on the GPhC register and contact it before injecting.¹² Our own registration is GPhC 9012878, and we supply genuine KwikPens through official LillyDirect supply from Eli Lilly's UK distribution.

Pens bought from sellers who offer to supply without a consultation or prescription carry extra risk, because you cannot trust the cold chain behind them. The MHRA publishes counterfeit alerts and runs the Yellow Card scheme for reporting problems.⁷

06 · Storing pens correctly

How to store Mounjaro so it does not freeze

Keep unopened pens in the fridge at 2–8°C and never let them freeze.¹³ Unopened pens keep until the expiry date printed on the box when they are stored properly.¹³

Practical habits that reduce the risk:

• Choose a middle shelf, in the main body of the fridge, not the door and not the back wall.
• Keep it clear of the freezer compartment and the cooling element, with space around the pen for air to move.
• Leave it in its carton so it is shielded from direct cold and from light.
• Keep the pen cap on to protect the pen from light.¹³
• Check the fridge itself. If other food freezes in the same spot, adjust the setting or move the pens.
• Use a fridge thermometer if you want reassurance.

If your household fridge is unreliable, or you share a communal fridge, a small dedicated fridge can help. We cover that in our guide to a mini fridge for Mounjaro.

For the underlying question, our pages on whether Mounjaro needs to go in the fridge and whether it has to stay refrigerated explain the rules in full.

07 · Out of the fridge and travel

Out of the fridge: what is allowed, and the opposite risk

Once a pen is in use, it can be kept out of the fridge not above 30°C for up to 30 days, after which it should be discarded.¹³ That is useful for short trips and means an in-use pen does not have to live in the coldest part of the fridge.

This also points to a simple safeguard against freezing. If your fridge is unreliable and you are mid-pen, keeping the pen you are currently using somewhere cool and stable at room temperature not above 30°C is permitted within that window. Keep the other, unopened pens in the fridge.

For unopened pens that have been out of the fridge, do not rely on a day limit you read online. Figures circulating online often come from other countries' labels, so check with the pharmacy before using the pen rather than guessing.¹³

Travelling without freezing your pen

You can fly with Mounjaro. 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.¹³ Most holidays need no special arrangements because in-use pens tolerate up to 30 days not above 30°C. For hot climates, use an insulated pouch.

The same caution applies to cold packs: do not let the pen sit directly against a frozen gel pack. Wrap it or keep a barrier between them. Check destination rules for travelling with prescription injectables before you fly.

08 · Replacement and dosing

Getting a replacement and what it means for your next dose

Contact the pharmacy that supplied the pen as soon as you notice, because they are the right people to arrange a replacement and to advise on timing. If you buy through us, our prescribing team reviews dose timing and follow-up, and repeat orders re-check suitability. Nothing ships automatically.

Some practical points:

• Replacement is not automatic. If a pen is faulty, damaged or the wrong item, contact us within 3 days. A pen frozen after delivery in your own fridge is a conversation to have with the team, so tell us exactly what happened.
• Do not stretch or split a dose to bridge the gap. Ask your prescriber how to handle the timing of the next injection.
• Missed timing is rarely an emergency. A short delay while a replacement arrives is something your prescriber can advise on. Tirzepatide has a half-life of about five days, so the medicine does not vanish overnight.¹ After a final dose it takes four to five weeks to clear the system.

A short pause while a replacement arrives is a practical issue to discuss with your prescriber, not a reason to inject a compromised pen.

We offer free next-day tracked delivery in temperature-controlled packaging, with same-day dispatch when ordered by 3pm, so a replacement does not take long to arrange once approved. See our weight loss clinic for how treatment works from consultation onwards.

09 · Feeling cold or tingling

Feeling cold or getting tingling on Mounjaro: a different question

These are separate matters from storage.

Feeling cold. If you feel unusually or persistently cold, particularly alongside tiredness, dizziness or low appetite, mention it to your prescriber. Eating very little can leave anyone feeling unwell, and a clinician can check whether something else is going on.

Tingling in the hands and feet. A change in skin sensation is listed as an uncommon side effect (up to 1 in 100) in the UK patient leaflet. Tell your prescriber if tingling is new, persistent or comes with numbness or weakness.¹³

In both cases, report new symptoms through the MHRA Yellow Card scheme, which helps regulators monitor medicines.¹⁹ Get medical help straight away for anything severe or sudden, including severe, persistent stomach pain, swelling of the face or throat, or difficulty breathing.

10 · Related storage guides

More on Mounjaro and the fridge

• If your pen has frozen, our short guide on what to do when you accidentally froze Mounjaro repeats the key steps.
• For the basics of refrigeration, see whether Mounjaro goes in the fridge.
• To see how a freezing incident differs from other storage accidents, read what happens when Mounjaro has frozen.

All of them point to the same rule: store pens at 2–8°C, never freeze them, and when in doubt ask the pharmacy before you inject.