Differing opinions about how to best care for insulin are stirring up a whirlwind of confusion. Over the last few months readers have been sending their questions and concerns to DIABETES HEALTH. The questions are simple enough: What is the best temperature to keep my insulin? Is it okay to use insulin past the expiration date? How should I mix my insulin? But answers to these questions can vary, making it hard to be sure one is doing the right thing. Here the questions and comments of insulin users will be presented with the recommendations of the companies who produce insulin.
Too Hot or Too Cold?
Brian Leslie, a DIABETES HEALTH on-line reader, writes: “I have had great results keeping my vial of insulin at work in my desk … However, I would imagine that taking a vial of medication and constantly fluctuating its temperature would tend to degrade its effectiveness faster.”
According to Wayman Wendell Cheatham, MD, medical director at Novo Nordisk, it is okay to keep insulin in and out of the refrigerator while the vial is in use. But prior to being opened, a vial of insulin should be stored in a refrigerator.
“As long as the insulin is kept away from high temperatures and freezing, a change in temperature (while in use) is not a problem,” says Dr. Cheatham. He adds that insulin should not be left in the car during the summer months even if only for a short period of time.
Laura Stallman, a spokesperson for Eli Lilly and Company, agrees that moving a vial of insulin in and out of the refrigerator while in use does not affect its potency – assuming that it is used before the expiration date.
Best If Used By…
Eli Lilly and Novo Nordisk, the only two companies who market insulin in the United States, provide directions and expiration dates with their product. But, some misunderstanding still arises.
The expiration date is printed on every vial of insulin, and neither company recommends using the product after the expiration date.
In educational material distributed by Eli Lilly, an example is given on how to accurately apply an expiration date: “If you start a new bottle of NPH on March 1 and you plan to finish it on or beyond March 28, you should not buy a bottle with an expiration date later than March 28.”
“Insulin is not like Cinderella. At the stroke of midnight it doesn’t disintegrate.” says Cheatham, of Novo. However, he adds, “Our data on hand does not support recommendations of use beyond that point (the expiration date).”
Kirti Pandya, RPh, from Novo Nordisk says that insulin kept at room temperature is good for 30 days after the vial has been opened and good for 90 days after opening if it is kept refrigerated. She adds that 70/30 and NPH insulin in prefilled pens are good for seven days at room temperature and that Regular in prefilled pens is good for 30 days at room temperature.
Eli Lilly and Co. says a vial of insulin, after the first use, can be kept and used up to 28 days if it is stored below 86 degrees F and not allowed to freeze. John Holcombe, MD, senior clinical researcher at Eli Lilly, adds that it is “perfectly okay” to leave the insulin at room temperature when in use. He also recommends insulin be kept away from heat and direct light.
To Shake or To Roll – That is the Question
Failure to mix insulin properly could decrease its effectiveness and increase day-to-day blood sugar fluctuation. Clinical studies confirm that proper mixing decreases the chance of irregular concentrations of insulin. Still, it is reported that people with diabetes tend not to mix their insulin sufficiently.
One reason for this could be the seemingly never-ending exchange of opinions within the diabetes community about how to mix insulin. While this exchange is by all means necessary, it can sometimes leave an insulin user wondering if there is a right or wrong way to ensure proper suspension of insulin.
In each vial of insulin the hormone is suspended in liquid. All NPH insulin, as well as Lente and Ultralente (all cloudy insulins), need to be mixed to ensure uniform suspension of the insulin within the liquid. No special measure needs to be taken with Regular and fast-acting insulin (Humalog) to assure proper suspension.
The aspect that seems to be causing the most confusion is the proper mixing technique – shaking versus rolling the vial. Eli Lilly representative Laura Stallman says users are advised to gently shake, turn the bottle over from end to end a few times, or roll the bottle gently between the palms of the hands to appropriately mix the insulin; Novo Nordisk strongly urges their customers to roll the vial without shaking. Novo cautions against shaking because it could create air bubbles in the vial. Shaking can create bubbles so small that a person cannot see them, says Dr. Cheatham.
“The air bubbles expand the volume of the insulin, so when insulin is drawn into the syringe, the individual will not get the proper amount of insulin. The syringe might appear to be filled to six units, but there could actually only be five units there,” says Cheatham.
Cheatham recommends rolling NPH, 70/30 and Lente between the hands for approximately ten to 15 cycles, or until the solution is uniformly opaque.
No matter what technique is used, a study presented at the 1996 meeting of the European Association for the Study of Diabetes found that the average insulin user fails to attain proper suspension before injecting. In the study researchers monitored insulin users before they injected. They found that most users shake or roll their insulin only four times before injection. The study recommends that a vial of insulin be rolled or tipped 20 times to achieve a satisfactory mixture.
DIABETES HEALTH plays an active role in diabetes education and it is our goal to disseminate accurate information to our readers. The questions sent in by our readers helps us keep track of the current concerns within the diabetes community as well as provide our readers with interesting articles. Please keep your questions coming.