Insulin is a medication that helps individuals manage diabetes by regulating blood sugar levels. Understanding how to properly handle and store insulin is crucial for maintaining its effectiveness. A common question concerns its stability once a vial, pen, or cartridge has been opened. Proper storage ensures the medication remains potent and safe for use.
Duration of Opened Insulin
Once insulin is opened or removed from refrigeration, its shelf life significantly shortens compared to its unopened expiration date. Most types of insulin, whether in vials, pens, or cartridges, are typically suitable for use for approximately 28 days when stored at room temperature (59°F to 86°F / 15°C to 30°C). This timeframe applies to many common insulins, including insulin glargine (Lantus), insulin lispro (Humalog), and insulin aspart (NovoLog).
For insulin vials, the 28-day countdown begins once the rubber stopper is punctured, regardless of refrigeration. Some insulin preparations have different durations; for example, insulin detemir (Levemir) can last up to 42 days, and insulin degludec (Tresiba) up to 56 days. Conversely, some formulations, like certain Humulin N or Humulin 70/30 pens, might have shorter durations (10 to 14 days). Always follow the manufacturer’s specific instructions on the product’s package insert.
Factors Influencing Insulin Stability
Several external factors can accelerate insulin degradation, making it less effective. Insulin is a protein, and its molecular structure is sensitive to environmental conditions. Exposure to extreme temperatures, both hot and cold, can cause irreversible changes.
High temperatures, exceeding 86°F (30°C), can denature the insulin protein, leading to a loss of its biological activity. This can occur if insulin is left in a hot car, direct sunlight, or near heat sources.
Freezing insulin is also damaging. When insulin freezes, ice crystals form, disrupting protein molecules and causing them to degrade rapidly. Even if thawed, frozen insulin should not be used. Excessive physical agitation, such as vigorous shaking, can also contribute to insulin degradation by breaking down protein molecules and potentially causing clumping or frothing.
Risks of Using Compromised Insulin
Using insulin that has lost potency due to improper storage carries health risks. The primary danger is that the insulin will not effectively lower blood glucose levels, leading to hyperglycemia (elevated blood sugar). Persistent hyperglycemia can cause symptoms like increased thirst, frequent urination, and fatigue.
Uncontrolled hyperglycemia can lead to complications such as diabetic ketoacidosis (DKA), a medical emergency more common in individuals with type 1 diabetes. DKA occurs when the body breaks down fat for energy, producing harmful ketones. Compromised insulin may show visual cues like changes in color, cloudiness (for clear insulins), or the presence of clumps, particles, or frost-like crystals. However, insulin can lose effectiveness without visible changes, making adherence to storage guidelines important.
Best Practices for Storage and Disposal
Unopened insulin should always be stored in a refrigerator at temperatures between 36°F and 46°F (2°C and 8°C) until its expiration date. Avoid placing insulin near the freezer compartment, as freezing can render it unusable.
Once opened, most insulin products can be stored at room temperature (59°F to 86°F / 15°C to 30°C) for their specified duration, usually up to 28 days. Labeling the insulin with the date of opening helps track its usable period. Keep insulin away from direct sunlight, extreme heat, and cold, such as in a car or on a windowsill. When traveling, an insulated bag can help maintain the recommended temperature, avoiding direct contact with ice packs.
Safe disposal of insulin and related supplies is important. Expired or unused insulin should be discarded according to local regulations. Used syringes, needles, and insulin pens with attached needles should be placed in a sharps container to prevent accidental needle sticks. Many communities offer specific programs for sharps disposal, such as drop-off sites or mail-back services.