Insulin levels differed by up to 23% and glycemic control varied up to 62% depending on whether the pen was shaken or not.
ReutersHealth.comrecently reportedon a study out of Italy stating that shaking the neutral protamine Hagedorn (NPH) insulin pen, as well as the angle at which it is injected, matters greatly in terms of the amount of insulin that enters the bloodstream.
The researchers set out to learn what would happen to a patient’s blood glucose levels if he/she did not tip the NPH pen 20 times in a back and forth motion prior to injection. Additionally, the researchers wanted to learn the effect of the position of the pen at the time of injection. The results of the study showed high degrees of variations in patients’ blood glucose levels as a result of the pen not being properly shaken and the position of the pen.
When the pen was not shaken and facing down, more insulin entered the bloodstream, while less insulin entered the bloodstream if the needle was lying flat or tilted upwards. This coincided with the rate of onset — faster if needle was pointing down, slower if needle was lying flat or tilted upwards. Therefore, a consequence of not shaking the pen is the possibility of unpredictable glycemic control. The research team found that insulin levels differed by up to 23% and glycemic control varied up to 62% depending on whether the pen was shaken or not.
Because of the degree of variability due to technique with NPH insulin, Dr. Satoru Yamada from Kitasato Institute Hospital, Tokyo, Japan, suggested that doctors use long-acting insulins rather than NPH insulin. This is a viable option if patients can afford the more expensive long-acting insulins. For those who cannot, providers should remind patients that NPH insulin must always be re-suspended according to its specific package labeling.