Written and maintained by CASRAI Editorial Board
Last updated
This page describes products and general use; it is not medical advice.
Short answer: it depends on whether the pen is unopened or in use. An unopened insulin pen is stored in a refrigerator at 2°C to 8°C (36°F to 46°F) until its expiration date. A pen that is in use is kept at room temperature, below 30°C (86°F), and the FDA-approved labels for NovoLog, Lantus and Humalog pens say not to refrigerate it. Each in-use pen is discarded after 28 days, even if insulin remains.
Who uses this: clinic and pharmacy staff who stock insulin, caregivers, and students learning about injectable-drug devices. Always check the label or instructions for use of the specific product, because storage rules are product-specific.
What an insulin pen is
An insulin pen is a prefilled, single-patient-use injector. On the NovoLog, Lantus and Humalog labels, the pen cartridge holds 3 mL of insulin (NovoLog FlexPen and FlexTouch, Lantus SoloStar, Humalog KwikPen). A pen is different from a vial, which is a bottle of insulin drawn into a syringe; the labels give vials separate storage rules. For the syringe side, see what a syringe is and insulin syringe sizing. A pen is also a kind of medical device used to deliver a drug.
Does an unopened insulin pen need to be refrigerated?
Yes. The labels for NovoLog, Lantus and Humalog all direct that unused insulin be stored in a refrigerator, and list unopened refrigerated storage as lasting until the expiration date printed on the product. The NovoLog and Lantus labels give the range as 2°C to 8°C (36°F to 46°F). Do not freeze it, and do not use insulin that has been frozen. Protect it from direct heat and light.
An unopened pen may be kept at room temperature (up to 30°C or 86°F) for 28 days, then must be thrown away.
Does a pen in use need to be refrigerated?
No. For the pens in the table below, the in-use pen is kept at room temperature and the labels say not to refrigerate it (NovoLog: “Do not refrigerate”; Lantus and Humalog: room temperature only). The patient instructions for NovoLog say the pen in use is thrown away after 28 days, even if it still has insulin left in it.
Storage by product (from the FDA-approved labels)
| Product (3 mL pen) | Unopened, room temperature (up to 30°C / 86°F) | Unopened, refrigerated | In use (opened) |
|---|---|---|---|
| NovoLog FlexPen / FlexTouch (insulin aspart), Novo Nordisk | 28 days | Until expiration date | 28 days; do not refrigerate |
| Lantus SoloStar (insulin glargine), Sanofi | 28 days | Until expiration date | 28 days; room temperature only, do not refrigerate |
| Humalog KwikPen, Tempo Pen, Junior KwikPen (U-100) and U-200 KwikPen (insulin lispro), Eli Lilly | 28 days | Until expiration date | 28 days; room temperature only, do not refrigerate |
The Humalog label adds that room-temperature days are cumulative: at room temperature the product can be used for a total of 28 days, counting both unopened and in-use storage time. The table covers only these three products; follow the label of the product you hold.
Pens versus vials
Vials follow different rules. In the same labels, an in-use vial (10 mL for NovoLog and Lantus; 10 mL and 3 mL for Humalog) may be stored either refrigerated or at room temperature for 28 days, while an in-use pen may not be refrigerated. Do not assume the vial rule applies to a pen.
Heat, light and freezing
- Do not freeze insulin, and do not use it if it has been frozen (NovoLog, Lantus and Humalog labels).
- Protect from direct heat and light (NovoLog, Lantus and Humalog labels); NovoLog also warns against excessive heat or light.
- For insulin in an insulin pump reservoir, the Humalog label says to change it at least every 7 days or per the pump manual, or after exposure to temperatures above 37°C (98.6°F).
Common mistakes
- Putting the pen in use back in the refrigerator because the unopened pen was kept there.
- Counting 28 days from first injection only, when the product label counts room-temperature storage time before opening as well (Humalog footnote).
- Drawing insulin from a pen into a syringe for later use. The NovoLog label says not to withdraw it into a syringe and store it.
- Storing the pen with a needle attached. The NovoLog label says to remove and discard the needle after each injection and store the pen without a needle attached.
- Using a pen that has frozen.
FAQ
Does an insulin pen need to be refrigerated?
Unopened pens are stored in the refrigerator (2°C to 8°C) until the expiration date. Once a pen is in use, the NovoLog, Lantus and Humalog labels direct room-temperature storage below 30°C (86°F) and say not to refrigerate it. Discard after 28 days.
How long can an unopened pen stay out of the refrigerator?
Twenty-eight days at up to 30°C (86°F) on the NovoLog, Lantus and Humalog labels, after which it is thrown away.
Can I freeze insulin pens?
No. The NovoLog, Lantus and Humalog labels say not to freeze insulin and not to use it if it has been frozen.
For broader supply and storage context, see the diabetes clinic supply checklist and pharmaceutical cold chain logistics.
Sources
- NovoLog (insulin aspart) Prescribing Information and Patient Information, Novo Nordisk, revised 02/2023, sections 16.2 and Table 9: novo-pi.com/novolog.pdf (checked 2026-10-30).
- Lantus / Lantus SoloStar (insulin glargine) label, Sanofi, effective 2025-06-02, section 16.2, via DailyMed: DailyMed set ID d5e07a0c-7e14-4756-9152-9fea485d654a (checked 2026-10-30).
- Humalog (insulin lispro) label, Eli Lilly, SPL published 2026-08-10, section 16.2, via DailyMed: DailyMed set ID c8ecbd7a-0e22-4fc7-a503-faa58c1b6f3f (checked 2026-10-30).
