Insulin is a medication used to manage blood sugar levels for individuals with diabetes. Its effectiveness relies heavily on its stability, which is maintained through proper storage conditions. Ensuring its integrity is crucial for patient safety.
How Insulin Degrades
Insulin is a protein with a complex molecular structure, including two chains linked by disulfide bonds. This structure is susceptible to changes when exposed to certain environmental factors. High temperatures, freezing temperatures, direct sunlight, and excessive physical agitation can alter the insulin molecule. These alterations can lead to a loss of potency.
The degradation process often involves protein denaturation, where the insulin molecule loses its intended three-dimensional shape. This can lead to aggregation, where insulin molecules clump together, forming insoluble particles. Chemical breakdown, such as the cleavage of disulfide bonds or the formation of inactive fragments, also occurs. Once insulin has degraded, these changes are generally irreversible.
Identifying Compromised Insulin
Visual inspection can sometimes reveal if insulin has degraded. Clear insulin, such as regular or rapid-acting insulin, should appear colorless and transparent. If clear insulin looks cloudy, discolored, or contains visible particles or clumps, it is compromised and should be discarded.
Some insulin types, like NPH (isophane) insulin or pre-mixed insulins, are normally cloudy or opaque due to their formulation. These should appear uniformly cloudy without any distinct clumps, threads, or particles, even after gentle rolling to mix. If you observe any unusual changes in consistency, such as a frosted appearance or particles sticking to the glass, it suggests degradation.
Insulin can degrade without obvious visual cues. The most reliable indicator of compromised insulin is consistently high blood sugar levels despite proper dosing and administration technique. If blood glucose readings are unexpectedly elevated, even after confirming correct insulin use and storage, the insulin has lost its effectiveness. If you suspect your insulin is not working as expected, consult a healthcare professional.
Proper Storage and Handling
Unopened insulin vials and pens should be stored in a refrigerator at temperatures between 36°F and 46°F (2°C and 8°C). When stored under these conditions, unopened insulin maintains its potency until the expiration date printed on the package. Avoid placing insulin directly against freezer coils, as freezing temperatures can damage it.
Once opened, insulin vials or pens can be kept at room temperature, between 59°F and 86°F (15°C and 30°C). Most opened insulin products remain stable for about 28 days, though some specific types may last anywhere from 10 to 56 days. Write the date you open a new vial or pen on its label to track its use-by date.
When traveling, protect insulin from extreme temperatures. Do not leave insulin in direct sunlight or a hot car, as heat can reduce its potency. If insulin has been accidentally frozen, do not use it, even after thawing, as its potency will be compromised.
If insulin has been exposed to temperatures exceeding 86°F (30°C), it may have lost effectiveness. While it might be necessary to use such insulin in an emergency, replace it with properly stored insulin as soon as possible. Never attempt to compensate for potentially compromised insulin by increasing the dosage, and always consult a pharmacist or doctor if you have concerns about your insulin’s integrity.