Insulin is a naturally occurring hormone that plays a significant role in regulating blood glucose levels. For individuals with diabetes, insulin therapy is often necessary to manage these levels effectively. The consistent effectiveness of this medication relies on proper storage and an understanding of its shelf life.
Storing Unopened Insulin
Unopened insulin products require specific storage conditions to maintain their stability and effectiveness until their printed expiration date. Manufacturers generally recommend storing unused insulin in a refrigerator, typically at temperatures between 36°F and 46°F (2°C and 8°C). This helps preserve the insulin’s protein structure, preventing premature degradation.
This guideline applies to various forms of unopened insulin, including vials, pre-filled pens, and cartridges. Protecting these unopened products from light is also important for their long-term preservation.
Using Opened Insulin
Once insulin is opened or removed from refrigeration, its shelf life shortens, and storage recommendations change. Most opened insulin, whether in vials, pens, or cartridges, should be stored at room temperature, generally between 59°F and 86°F (15°C and 30°C). Storing opened insulin at room temperature can prevent discomfort from injecting cold medication.
The typical duration for using opened insulin is 28 days. However, this period can vary depending on the specific insulin type or brand. For instance, some insulins like Levemir may be stable for up to 42 days, while Tresiba can last for 56 days once opened. Insulin used in pump reservoirs has an even shorter lifespan and should be discarded after 48 hours. Note the date of opening on the product to track its usage period.
Preserving Insulin’s Potency
Environmental factors can negatively impact insulin’s stability and shorten its shelf life. Extreme temperatures are particularly detrimental; exposing insulin to freezing conditions can destroy its protein structure, rendering it ineffective. Likewise, excessive heat, such as leaving insulin in a hot car or direct sunlight, causes the insulin to break down and lose its ability to regulate blood glucose.
Physical agitation, such as vigorous shaking, can also degrade insulin’s delicate protein molecules. Instead of shaking, insulin vials or pens that require mixing should be gently rolled between the palms to ensure an even suspension. To prevent premature degradation, insulin should be kept away from direct heat sources and direct sunlight.
Recognizing Compromised Insulin and Its Risks
It is important to identify insulin that may have lost its effectiveness, even if within its stated expiry or opened-use window. Clear insulin, such as regular or rapid-acting types, should remain transparent. If it appears cloudy, discolored, or contains particles, clumps, or “strings,” it has likely been compromised and should not be used. Some intermediate-acting insulins, like NPH, are naturally cloudy, but any changes in their usual appearance, such as clumping or a frosty appearance, indicate a problem.
Using degraded insulin will not regulate blood sugar levels as intended. This can lead to dangerously high blood sugar (hyperglycemia), potentially causing complications like diabetic ketoacidosis. If there is any doubt about the integrity of an insulin product, dispose of it properly and use a new supply.