Insulin Storage & Expiration
By Ryan Mitchell · Referenced to manufacturer labeling & FDA guidance · Updated July 2026
Insulin is a protein, and proteins degrade with heat, light, agitation and time. Degraded insulin doesn't usually look different — it just quietly works less, which shows up as unexplained high readings. The rules below cover the two storage states every insulin has: unopened (in the fridge) and in use (opened).
The two golden rules
- Unopened insulin lives in the refrigerator at 36–46°F (2–8°C) and is good until the printed expiration date. Never frozen — freezing permanently destroys insulin, even after thawing.
- Opened (in-use) insulin can stay at room temperature — below 77–86°F (25–30°C) depending on product — but only for a limited number of days, regardless of the printed date.
In-use timelines by product
| Insulin | Room temp, opened | Notes |
|---|---|---|
| Humalog / NovoLog / Apidra (rapid vials & pens) | 28 days | Apidra pens: 28 days below 77°F |
| Humulin R / Novolin R (Regular) | 28–42 days (product-specific) | Novolin vials list 42 days |
| NPH (Humulin N / Novolin N) | 14–42 days (pen vs vial varies) | Cloudy — roll gently before use |
| Lantus / Basaglar (glargine U-100) | 28 days | Pens never refrigerated after first use |
| Toujeo (glargine U-300) | 56 days | |
| Levemir (detemir) | 42 days | |
| Tresiba (degludec) | 56 days | Longest in-use window |
| Vetsulin / Caninsulin (U-40, veterinary) | 42–60 days per label | Refrigerate between uses |
Write the opening date on every vial or pen the day you start it. Planning refills around these windows is exactly what our vial, pen and refill calculators do.
Signs insulin has gone bad
- Clear insulins (rapid analogs, glargine, detemir, degludec) turned cloudy, discolored, or containing particles or strings.
- Cloudy insulins (NPH, premixed) with clumps that won't disperse after gentle rolling, or a frosted coating inside the glass.
- Behavioral sign: unexplained persistent highs despite correct dosing — especially after heat exposure (car, direct sun, no fridge) — warrant swapping to a fresh vial/pen before assuming your doses are wrong.
Travel and heat
- Carry insulin in hand luggage — checked baggage holds can freeze it.
- Use an insulated pouch or cooling case in hot climates; avoid direct ice contact (freeze risk) — gel packs with a barrier are safer.
- Insulin tolerates the days-long room-temperature windows above; a normal travel day is fine. The dangers are cars in summer, radiators, and freezing.
- Crossing time zones changes basal timing, not storage — plan dose timing with your care team before long trips.
Can you use expired insulin?
Manufacturers and the FDA say no — potency after the expiration date or beyond the in-use window is not guaranteed, and dosing accuracy depends on full potency. In practice degradation is gradual rather than a cliff, which is why the universal advice for unexplained highs on old insulin is: open a fresh one first. If cost pressure is forcing the question, ask your care team about patient-assistance programs rather than stretching expired insulin — and use the pens-per-month calculator to make prescriptions cover the real need.
Sources & References
- FDA. Information Regarding Insulin Storage and Switching Between Products in an Emergency. Link
- Manufacturer prescribing information: Lilly (Humalog, Humulin), Novo Nordisk (NovoLog, Levemir, Tresiba), Sanofi (Lantus, Toujeo, Apidra).
- ADA. Insulin Storage and Syringe Safety. Link
Last reviewed: July 2026 · See our methodology