As daylight savings time approaches this weekend, I want to share a story about a recent encounter my colleague Naveen Kakumanu, MD, of Michigan State University’s endocrine clinic, had with a well-informed patient who used an insulin pump.
The patient presented with recent, unexplained nocturnal hypoglycemic episodes that occurred for 2 weeks before the clinic visit. Upon meticulous evaluation, Dr. Kakumanu detected that the patient’s insulin pump time setting was off by 12 hours — the a.m. and p.m. settings were flipped. Since there was a significant difference between the patient’s daytime and night-time basal insulin dose settings, the patient was receiving more insulin than required at night. Additionally, the patient used two bolus settings (carb ratios of 10 and 15), so, the a.m. and p.m. time switch not only affected the basal rates, but also the bolus dosing. In retrospect, the patient reported having changed the pump batteries about 2 weeks prior, coinciding with the nocturnal hypoglycemic events.
The reasons daylight savings time affects people with diabetes using insulin pumps are two-fold.
Fortunately, these events were not life threatening for this patient. However, this example underscores the importance of patients and their caregivers remembering to check their insulin pump’s time settings after the clocks “spring forward” by 1 hour this Sunday. Health care providers, too, should remember to remind their patients about this change and how it can affect insulin pumps and any diabetes device with an internal clock setting.
The reasons daylight savings time affects people with diabetes using insulin pumps are two-fold: Insulin pumps' internal clocks do not automatically adjust time or date settings, and the pumps that are commercially available (to my knowledge) are not connected to GPS or other automatically adjusting central sources.
On the other hand, insulin dosing by the insulin pump — basal and bolus — depends on correct time and date settings on the internal clock of the pump. The pump should always be in sync with ambient time.
To avoid redundancy, the details of the mechanistic technology of basal and bolus insulin dosing and its relation to correct time settings can be reviewed in previous posts, as well as in our review article that was published in the Journal of Diabetes Science and Technology in 2014 and reported by Endocrine Today.
As also detailed in prior posts, another perhaps more serious glitch may result from incorrect a.m. and p.m. settings. There is a potential risk of harm if such glitches result in significant errors in insulin dosing. The harm is related to over- or underdosing insulin, potentially resulting in hypoglycemia or hyperglycemia. The 1-hour change may not impact the basal rates significantly; however, the change may impact the bolus dosing if the patient uses more than one setting for meals. This can occur at lunch time in particular. A mix-up can occur because many patients eat lunch between11:30 a.m. and noon, and most bolus settings change from breakfast to lunch at 11 a.m..