Mounjaro Storage Guide (2026)
Refrigeration, the 21-day room-temperature window, what to do if it freezes or overheats, and travel rules. Verified against the current Lilly Prescribing Information.
Mounjaro must be refrigerated at 36 to 46 degrees Fahrenheit (2 to 8 degrees Celsius) in its original carton, protected from light. It can be kept at room temperature up to 86 degrees Fahrenheit (30 degrees Celsius) for up to 21 days, but only one time. After that 21-day window the pen must be discarded. Do not freeze Mounjaro; if it freezes, discard it. Mounjaro and Zepbound share the same Lilly tirzepatide formulation, so the storage rules are identical.
Mounjaro and Zepbound are both Lilly tirzepatide in the same pen and KwikPen formats. Every storage rule on this page applies identically to both. The full pillar with hot-car scenarios, ice-pack travel rules, and product-by-product (vial, single-dose pen, KwikPen) breakdown lives on the Zepbound storage guide.
The five storage rules
The 21-day room-temperature window is the rule most patients get wrong. Read it carefully.
In the original carton, protected from light. This is the default storage condition until you are ready to inject.
One-time window. Once the pen has been at room temperature, it cannot be returned to refrigerated storage and must be discarded after 21 days regardless of remaining doses.
If Zepbound has frozen, even partially, discard the pen. Do not attempt to thaw and use it. Frozen tirzepatide can lose potency and the pen mechanism can crack.
Gentle handling only. Vigorous shaking can damage the protein structure of tirzepatide.
Keep the pen in its original carton until you are ready to inject. Direct sunlight or prolonged bright light exposure can degrade the medication.
Common scenarios
The same scenarios apply to Mounjaro: the overnight room-temperature lapse, the hot car, the accidental freeze, the cross-country flight, the microdosing question. The scenario-by-scenario breakdown is on the Zepbound storage page.
Travel rules
Carry-on allowed. Yes. TSA's medical-conditions guidance allows GLP-1 medications and accompanying gel ice packs in carry-on luggage.
Ice packs. Frozen or partially frozen ice packs are allowed in carry-on if they are accompanying medically necessary medications. Declare them at the security screening point.
Documentation. TSA does not require a prescription label, but having one (or the original prescription box) speeds up the screening process if you are asked.
Frequently asked questions
Storage rules come directly from the Mounjaro (tirzepatide) Prescribing Information from Eli Lilly. Mounjaro and Zepbound use the identical tirzepatide formulation, so the storage protocol is shared. Travel and TSA guidance is the same as for any GLP-1 injection.