How Long Can I Leave Mounjaro Unrefrigerated? (October 2026)

01 · The core answer

How long can an in-use pen stay out of the fridge?

An in-use pen can be out of the fridge for up to 30 days (not above 30°C). Once in use, a pen can be kept out of the fridge not above 30°C for up to 30 days — useful for short trips — and must then be thrown away.¹ Discard it at that point even if some medicine is left.

Keep the cap on to protect the pen from light, and never use a pen that has been frozen.¹³ Each KwikPen contains four weekly doses, so a pen used every week will normally be finished well inside this window.¹

02 · Unopened pens

What if the pen is unopened?

For an unopened pen, the rule is different: keep it in the fridge, and it keeps until the expiry date printed on the box.¹ 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. Figures circulating online often come from other countries' labels.¹³

If you have just received a delivery and are unsure, our team can advise. Orders ship in temperature-controlled packaging, and you can see the Mounjaro pen and its current price on the product page.

Related guides: How Long Can Wegovy Be Unrefrigerated? and How long can you leave mounjaro out of the fridge and How long does mounjaro last unrefrigerated.

03 · Warm or frozen pens

What happens if Mounjaro gets warm, and how can I tell if it has gone bad?

A pen that has been warm is only usable if it stayed within the in-use limits: not above 30°C and within 30 days of starting to keep it out of the fridge.¹ A hot car or a sunny windowsill is the classic way to exceed that. The pharmacy can tell you what to do with an unopened pen that has been exposed to heat.

The solution in a genuine pen is clear and colourless; do not use a pen that looks cloudy or discoloured or has particles in it. Also check these points: has it been frozen, has it passed the in-use limit, and is it past the printed expiry date? A frozen pen must never be used.¹ If you are unsure about any of these, do not inject. Contact the pharmacy, or see our guide on leaving Mounjaro out overnight.

04 · Flying with pens

How do I travel with Mounjaro on a plane?

You can fly with Mounjaro. Carry pens in hand luggage, because hold luggage can fall below freezing. Ideally use a cool bag, with the prescription label or a copy of your prescription.¹

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 Check destination rules for travelling with prescription injectables before you fly. Airline and airport rules on injectable medicines differ, so confirm them with your airline.

05 · Holidays and missed doses

Can I stop Mounjaro for a holiday?

Most people do not need to pause for a holiday, because an in-use pen can be kept out of the fridge for up to 30 days (not above 30°C).¹ If you decide to pause or change anything, speak to your prescriber first.

If a trip makes you miss your usual day, this rule applies: 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 Our guide to the gap between Mounjaro injections explains this in more detail.

06 · Same rule, other brands

Do other weight-loss pens follow the same rules?

Not necessarily. Each medicine has its own leaflet and its own storage limits, so never assume one pen's rules apply to another. For wider support on treatment, visit our weight loss clinic.