Improperly stored insulin is a common cause of erratic or high blood sugars, and should be considered if there is a change in the patient's glycemic control, or if a patient does not seem to be responding to his insulin as usual, especially when traveling. Patients should be given the following instructions:
• Do not leave insulin in luggage or a car that might be exposed to extreme temperatures.
Unopened vials, pens, and pen cartridges should be stored in the refrigerator at 36°F-46°F (2°C-8°C) until the expiration date. Once opened (when the stopper or seal has been punctured with a needle), insulin pens are kept at room temperature. Vials can be refrigerated or unrefrigerated, depending on what is more convenient for the patient. Once opened, vials are "fresh" for 28 days if stored at less than 86°F (15°C-30°C) and protected from bright sunlight. In contrast, pen products vary in the manufacturers' allowable time before discarding (Table 2). rnsulin that has passed the expiration date, or has been exposed to other than recommended temperatures, will lose potency and should be discarded.
Shaking or agitating insulin, such as when carrying it in a purse or loose in a car glove box, can reduce its potency. Hard shaking of long-acting insulin suspensions prior to drawing it up in a syringe can have the same effect. Cold insulin can be irritating to inject. Thus, patients should be told to roll the vial in their hands 10 times prior to drawing it up in the syringe (after letting it sit 30 minutes at room temperature if the vial is stored in the refrigerator).
Drawing up several days' worth of syringes is a common practice, especially for individuals who require assistance from home health workers, visiting nurses, or family. Prefilled syringes should be kept refrigerated, stored vertically with the needles pointing up to prevent needle clogging by insulin crystals, and used within 21 days. Always label them carefully.
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