Insulin Storage & Expiration
Medically reviewed by Dr. Chhaya Makhija, MD, DipABLM — September 2026
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.
Frequently Asked Questions
How long does insulin last once opened?
Most insulin vials and cartridges, opened or unopened, can sit unrefrigerated between 59°F and 86°F (15–30°C) for up to 28 days and still work. After 28 days potency declines even at proper room temperature, so an in-use vial should be discarded at that point regardless of the printed expiry date. Product labels vary, so check yours.
Can I use insulin after its expiry date?
No. Degraded insulin is less potent, and the practical danger is that it silently under-treats — your glucose runs high and the cause is not obvious. Write the date you open each vial or pen directly on it, and go by whichever comes first: 28 days from opening, or the printed expiry.
Does heat ruin insulin faster?
Yes, measurably. The usual 28-day room-temperature window shortens to roughly 21 days when insulin is kept at an average of around 90°F (32°C). Cars, windowsills, beach bags and checked luggage are the common failure points.
How can I tell if insulin has gone bad?
Inspect it before every use. Clear insulins should be completely clear and colourless — discard them if you see cloudiness, discolouration, clumps, stringiness, or crystals on the glass. Cloudy insulins such as NPH should resuspend evenly; if they stay clumped or leave solid deposits after gentle rolling, do not use them.
Can I freeze insulin?
Never. Freezing destroys insulin permanently, and it does not reliably look different afterwards, which is what makes it dangerous. Discard any insulin you suspect has frozen — including insulin left against a fridge’s cooling element or in an unheated car in winter.
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
Written by Ryan Mitchell · Last updated: September 2026