Insulin is a medication that helps manage blood sugar levels for individuals with diabetes. Its effectiveness relies heavily on proper storage, as it is a sensitive protein that can degrade when exposed to unsuitable environmental conditions, especially temperature extremes. Understanding how temperature impacts insulin and recognizing signs of degradation are important for maintaining its potency and ensuring proper diabetes management.
How Temperature Affects Insulin
Insulin’s structure and function are susceptible to temperature fluctuations. High temperatures cause insulin to denature, meaning its molecular structure changes, leading to a loss of effectiveness. This degradation can occur when insulin is exposed to temperatures above 86°F (30°C), and the longer the exposure, the greater the loss of potency. For example, insulin contained in an infusion set of a pump device should be discarded if exposed to temperatures exceeding 98.6°F (37°C). Leaving insulin in hot places like a car’s glove box or direct sunlight can rapidly diminish its ability to lower blood sugar.
Conversely, freezing temperatures also damage insulin. Insulin should never be frozen, as this can irreversibly alter its molecular structure, rendering it ineffective even after it thaws. Storing insulin too close to the freezer compartment in a refrigerator can cause it to freeze.
Signs of Insulin Degradation
Inspecting insulin visually before use can help identify degradation. Clear insulin should be colorless and transparent. If clear insulin appears cloudy, discolored, or contains particles, clumps, or “strings” floating in it, it has likely gone bad and should not be used.
Some types of insulin, such as NPH or intermediate-acting insulins, are naturally cloudy due to their formulation. For naturally cloudy insulins, signs of degradation include a frosted appearance, crystallization, separation where clumps settle at the bottom, or if it shows lumps, flakes, or sticks to the glass. Unexplained high blood sugar levels despite consistent dosing can also suggest that the insulin has lost its potency.
Storing Insulin Correctly
Unopened insulin vials or pens should generally be stored in a refrigerator at temperatures between 36°F and 46°F (2°C and 8°C) until their expiration date. It is important to avoid placing insulin too close to the freezer element within the refrigerator to prevent accidental freezing.
Once opened or in use, most insulin products can be kept at room temperature, typically between 59°F and 86°F (15°C and 30°C), for a specific duration, usually up to 28 days. Some insulins may have different in-use durations, with some lasting from 10 to 56 days depending on the specific type and manufacturer. Storing opened insulin at room temperature can make injections more comfortable, as cold insulin may sting. Insulin should always be protected from direct heat, sunlight, and humidity, and never left in hot environments like a car.
When to Dispose of Insulin
Insulin must be discarded under several circumstances to ensure safety and effectiveness. Any insulin showing visible signs of degradation should be thrown away immediately, even if it has not reached its labeled expiration date. Insulin that has been frozen or exposed to excessively high temperatures should also be discarded. Using insulin that has lost its potency can lead to uncontrolled blood sugar levels, potentially causing health complications.
Unopened insulin should not be used past the expiration date printed on its packaging. Once opened, insulin has a limited “in-use” period and should be discarded after this period, even if it looks normal. Used needles and syringes should be placed in a sharps container, and local guidelines should be followed for proper disposal of expired or compromised insulin vials and pens.