Insulin that's exposed to extreme temperatures can lose potency even if it still looks normal, so storage habits matter as much as the dose itself.
Unopened insulin
Store unopened pens and vials in the refrigerator (typically 36-46°F / 2-8°C) until the expiration date printed on the packaging. Never let insulin freeze - freezing permanently damages it, and it should be discarded if it has frozen, even after thawing.
In-use insulin
Once opened, most insulin can be kept at room temperature (below roughly 86°F / 30°C) for a limited window that varies by product - commonly around 28 days, though it varies by brand and should be checked against the specific product's insert. Keeping it in-use insulin at room temperature (rather than the fridge) can also make injections less stingy, since cold insulin can be more uncomfortable to inject.
Travel and heat
- Never leave insulin in a hot car, direct sun, or near a heater.
- Use an insulated travel case with a cool pack for trips, keeping insulin away from direct contact with ice (to avoid freezing).
- On flights, carry insulin in hand luggage - cargo holds can freeze.
When to discard insulin
Discard insulin that has been frozen, exposed to high heat, has changed color or clarity in a way that's unusual for that product, has visible particles (for a normally clear insulin), or is past its opened-use window or expiration date.